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Background: Preeclampsia poses a substantial clinical challenge, characterized by maternal hypertension, cardiac dysfunction, and persistent cardiovascular risks for both the mother and offspring. Despite the known roles of the estrogen receptor (GPER [G protein-coupled estrogen receptor]) in placental development, its impact on cardiovascular aspects within a preeclampsia animal model remains unexplored. We propose that G-1, a GPER agonist, could have the potential to regulate not only hypertension but also cardiac dysfunction in rats with preeclampsia., Methods: To explore the influence of G-1 on preeclampsia, we used the reduced uterine perfusion pressure (RUPP) model. RUPP rats were administered either G-1 (100 µg/kg per day) or hydralazine (25 mg/kg per day). We conducted echocardiography to probe the intricate cardiac effects of G-1., Results: The RUPP rat model revealed signs of hypertension and cardiac dysfunction and alterations in gene and protein expression within placental and heart tissues. G-1 treatment reduced blood pressure and reversed cardiac dysfunction in rats with preeclampsia. In contrast, administration of the vasodilator hydralazine reduced blood pressure without an improvement in cardiac function. In addition, while G-1 treatment restored the levels of sFLT-1 (soluble fms-like tyrosine kinase-1) in RUPP rats, hydralazine did not normalize this antiangiogenic factor., Conclusions: The therapeutic intervention of G-1 significantly mitigated the cardiovascular dysfunction observed in the RUPP rat model of preeclampsia. This discovery underscores the broader significance of understanding GPER's role in the context of preeclampsia-related cardiovascular complications., Competing Interests: None.

Certain classes of antihypertensive drug may exert specific, blood pressure (BP)-independent protective effects on end-organ damages such as left ventricular hypertrophy, although the overall evidence has not been definitive in clinical trials. To unravel antihypertensive drug-induced gene expression changes that are potentially related to the amelioration of end-organ damages, we performed in vivo phenotypic evaluation and transcriptomic analysis on the heart and the kidney, with administration of antihypertensive drugs to two inbred strains (ie, hypertensive and normotensive) of rats. We chose 6 antihypertensive classes: enalapril (angiotensin-converting enzyme inhibitor), candesartan (angiotensin receptor blocker), hydrochlorothiazide (diuretics), amlodipine (calcium-channel blocker), carvedilol (vasodilating β-blocker), and hydralazine. In the tested rat strains, 4 of 6 drugs, including 2 renin-angiotensin system inhibitors, were effective for BP lowering, whereas the remaining 2 drugs were not. Besides BP lowering, there appeared to be some interdrug heterogeneity in phenotypic changes, such as suppressed body weight gain and body weight-adjusted heart weight reduction. For the transcriptomic response, a considerable number of genes showed prominent mRNA expression changes either in a BP-dependent or BP-independent manner with substantial diversity between the target organs. Noticeable changes of mRNA expression were induced particularly by renin-angiotensin system blockade, for example, for genes in the natriuretic peptide system ( Nppb and Corin ) in the heart and for those in the renin-angiotensin system/kallikrein-kinin system ( Ren and rat Klk1 paralogs) and those related to calcium ion binding ( Calb1 and Slc8a1 ) in the kidney. The research resources constructed here will help corroborate occasionally inconclusive evidence in clinical settings.

Leptomeningeal anastomoses (LMAs) are pial collaterals that perfuse the penumbra and important for stroke outcome. We previously showed LMAs from SHRs (spontaneously hypertensive rats) were vasoconstricted compared with normotensive Wistar rats. Here, we investigated mechanisms by which hypertension causes LMA vasoconstriction. SHRs were treated with the ACE (angiotensin-converting enzyme) inhibitor captopril, an Ang II (angiotensin II)-independent antihypertensive agent hydralazine, or vehicle for 5 weeks in drinking water (n=8/group). A group of Wistar rats (n=8) had regular drinking water served as controls. Blood pressure was measured twice weekly by tail-cuff. LMAs were isolated and studied under pressurized conditions. Vasoreactivity of LMAs, including myogenic responses, reactivity to Rho-kinase inhibitor Y-27632, and nitric oxide were measured. Both captopril and hydralazine lowered blood pressure in SHRs similar to Wistar. However, only captopril normalized LMA increased tone compared with untreated SHRs (15±2% versus 50±3%; P <0.01) that was similar to Wistar (16±2%) but not hydralazine (38±6%; P >0.05). Vasodilatory response of LMAs to Y-27632 was impaired in SHRs compared with Wistar (28±3% versus 81±4%; P <0.01) that was restored by captopril (84±5%; P <0.01) and partially hydralazine (59±4%). LMAs from all groups constricted similarly to NOS (NO synthase) inhibition; however, the vasodilatory response of LMAs to the nitric oxide donor sodium nitroprusside was impaired in SHRs compared with Wistar rats (29±4% versus 80±2%; P <0.01) that was restored by captopril (84±4%; P <0.01), not hydralazine (38±8%; P >0.05). These results suggest that ACE inhibition during chronic hypertension reversed vascular dysfunction and hyperconstriction of LMAs that could improve stroke outcome by increasing collateral perfusion.

Mineralocorticoids have been implicated in the pathogenesis of diastolic heart failure. On the contrary, angiotensin (Ang)-(1-7) has emerged as a potential strategy for treatment of cardiac dysfunction induced by excessive mineralocorticoid receptor activation. A critical question about the cardioprotective effect of Ang-(1-7) in hypertensive models is its dependence on blood pressure (BP) reduction. Here, we addressed this question by investigating the mechanisms involved in Ang-(1-7) cardioprotection against mineralocorticoid receptor activation. Sprague-Dawley (SD) and transgenic (TG) rats that overexpress an Ang-(1-7) producing fusion protein (TG(A1-7)3292) were treated with deoxycorticosterone acetate (DOCA) for 6 weeks. After treatment, SD rats became hypertensive and developed ventricular hypertrophy. These parameters were attenuated in TG-DOCA. SD-DOCA rats developed diastolic dysfunction which was associated at the cellular level with reduced Ca(2+) transient. Oppositely, TG-DOCA myocytes presented enhanced Ca(2+) transient. Moreover, higher extracellular signal-regulated kinase phosphorylation, type 1 phosphatase, and protein kinase Cα levels were found in SD-DOCA cells. In vivo, pressor effects of DOCA can contribute to the diastolic dysfunction, raising the question of whether protection in TG was a consequence of reduced BP. To address this issue, BP in SD-DOCA was kept at TG-DOCA level by giving hydralazine or by reducing the DOCA amount given to rats (Low-DOCA). Under similar BP, diastolic dysfunction and molecular changes were still evident in DOCA-hydralazine and SD-low-DOCA, but not in TG-DOCA. In conclusion, Ang-(1-7) protective signaling against DOCA-induced diastolic dysfunction occurs independently of BP attenuation and is mediated by the activation of pathways involved in Ca(2+) handling, hypertrophy, and survival., (© 2015 American Heart Association, Inc.)

Most patients with essential hypertension do not exhibit substantial renal damage. Renal autoregulation by preventing glomerular transmission of systemic pressures has been postulated to mediate this resistance. Conversely, malignant nephrosclerosis (MN) has been postulated to develop when severe hypertension exceeds a critical ceiling. If the concept is valid, even modest blood pressure (BP) reductions to below this threshold regardless of antihypertensive class (1) should prevent MN and (2) lead to the healing of the already developed MN lesions. Both predicates were tested using BP radiotelemetry in the stroke-prone spontaneously hypertensive rats receiving 1% NaCl as drinking fluid for 4 weeks. Severe hypertension (final 2 weeks average systolic BP, >200 mm Hg) and MN (histological damage score 36±5; n=27) developed in the untreated stroke-prone spontaneously hypertensive rats but were prevented by all antihypertensive classes (enalapril [n=15], amlodipine [n=13], or a hydralazine/hydrochlorothiazide combination [n=15]) if the final 2-week systolic BP remained <190 mm Hg. More impressively, modest systolic BP reductions to 160 to 180 mm Hg (hydralazine/hydrochlorothiazide regimen) initiated at ≈4 weeks in additional untreated rats after MN had already developed (injury score 35±4 in the right kidney removed before therapy) led to a striking resolution of the vascular and glomerular MN injury over 2 to 3 weeks (post-therapy left kidney injury score 9±2, P<0.0001; n=27). Proteinuria also declined rapidly from 122±9.5 mg/24 hours before therapy to 20.5±3.6 mg 1 week later. These data clearly demonstrate the barotrauma-mediated pathogenesis of MN and the striking capacity for spontaneous and rapid repair of hypertensive kidney damage if new injury is prevented., (© 2014 American Heart Association, Inc.)

The objective of our study was to determine the effects of 2 antihypertensive drug dose schedules (PM dose and add-on dose) on nocturnal blood pressure (BP) in comparison with usual therapy (AM dose) in blacks with hypertensive chronic kidney disease and controlled office BP. In a 3-period, crossover trial, former participants of the African American Study of Kidney Disease were assigned to receive the following 3 regimens, each lasting 6 weeks, presented in random order: AM dose (once-daily antihypertensive medications taken in the morning), PM dose (once-daily antihypertensives taken at bedtime), and add-on dose (once-daily antihypertensives taken in the morning and an additional antihypertensive medication before bedtime [diltiazem 60-120 mg, hydralazine 25 mg, or additional ramipril 5 mg]). Ambulatory BP monitoring was performed at the end of each period. The primary outcome was nocturnal systolic BP. Mean age of the study population (n=147) was 65.4 years, 64% were men, and mean estimated glomerular filtration rate was 44.9 mL/min per 1.73 m(2). At the end of each period, mean (SE) nocturnal systolic BP was 125.6 (1.2) mm Hg in the AM dose, 123.9 (1.2) mm Hg in the PM dose, and 123.5 (1.2) mm Hg in the add-on dose. None of the pairwise differences in nocturnal, 24-hour, and daytime systolic BP was statistically significant. Among blacks with hypertensive chronic kidney disease, neither PM (bedtime) dosing of once-daily antihypertensive nor the addition of drugs taken at bedtime significantly reduced nocturnal BP compared with morning dosing of antihypertensive medications.

Arterial tone in muscular conduit arteries may influence pressure wave reflection through changes in diameter and pulse wave velocity. We examined the relative specificity of vasodilator drugs for radial artery and forearm resistance vessels during intrabrachial arterial infusion. The nitric oxide (NO) donors, nitroglycerine and nitroprusside, and brain natriuretic peptide were compared with the α-adrenergic antagonist phentolamine, calcium-channel antagonist verapamil, and hydralazine. Radial artery diameter was measured by high resolution ultrasound, forearm blood flow by strain gauge plethysmography, and pulse wave velocity by pressure recording cuffs placed over the distal brachial and radial arteries. Norepinephrine was used to constrict the radial artery to generate a greater range of vasodilator tone when examining pulse wave velocity. Despite dilating resistance vasculature, phentolamine and verapamil had little effect on radial artery diameter (mean dilation <9%). By contrast, for comparable actions on resistance vessels, nitroglycerine and nitroprusside but not brain natriuretic peptide had powerful actions to dilate the radial artery (dilations of 31.3 ± 3.6%, 23.6 ± 3.1%, and 9.8 ± 2.0% for nitroglycerine, nitroprusside, and brain natriuretic peptide, respectively). Changes in pulse wave velocity followed those in arterial diameter irrespective of the signaling pathway used to modulate arterial tone (R=-0.89, P<0.05). Basal tone in human muscular arteries is relatively unaffected by α-adrenergic or calcium-channel blockade, but is functionally or directly antagonized by NO donors. The differential response to NO donors suggests that there is potential to manipulate the downstream pathway to confer greater specificity for large arteries with a resultant decrease in pressure wave reflection and systolic blood pressure.

Prostaglandin E(2) is a major prostanoid found in the kidney and vasculature contributing to the regulation of blood pressure. The prostaglandin E(2) receptor EP1 has been shown to contribute to hypertension by mediating angiotensin II-dependent vasoconstriction, although its precise role is incompletely characterized. Disruption of the EP1 receptor in C57BL/6J mice reduced the incidence of mortality during severe hypertension induced by uninephrectomy, deoxycorticosterone acetate, and angiotensin II. Mortality was dependent on all components of the model. Death was a result of aortic aneurysm rupture or occurred after development of anasarca, each of which was reduced in EP1-/- mice. Mean arterial pressure was increased in treated EP1+/+ and EP1-/- mice; however, this elevation was significantly lower in EP1-/- mice. Blood pressure reduction via administration of hydralazine phenocopied EP1-/- mice. Thus, reduction in blood pressure by disruption of EP1 reduced incidence of mortality and decreased organ damage, suggesting that EP1 receptor blockade may be a viable target for antihypertensive therapy.

We found earlier that deoxycorticosterone acetate-salt treatment causes blood pressure-independent left ventricular hypertrophy, but only in male mice. To test the hypothesis that the estrogen receptor-β (ERβ) protects the females from left ventricular hypertrophy, we treated male and female ERβ-deficient (ERβ(-/-)) mice and their male and female littermates (wild-type [WT]) with deoxycorticosterone acetate-salt and made them telemetrically normotensive with hydralazine. WT males had increased (+16%) heart weight/tibia length ratios compared with WT females (+7%) at 6 weeks. In ERβ(-/-) mice, this situation was reversed. Female WT mice had the greatest heart weight/tibia length ratio increases of all of the groups (+23%), even greater than ERβ(-/-) males (+10%). Echocardiography revealed concentric left ventricular hypertrophy in male WT mice, whereas ERβ(-/-) females developed dilative left ventricular hypertrophy. The hypertrophic response in female ERβ(-/-) mice was accompanied by the highest degree of collagen deposition, indicating maladaptive remodeling. ERβ(+/+) females showed robust protective p38 and extracellular signal-regulated kinase 1/2 signaling relationships compared with other groups. Calcineurin Aβ expression and its positive regulator myocyte-enriched calcineurin-interacting protein 1 were increased in deoxycorticosterone acetate-salt female ERβ(-/-) mice, yet lower than in WT males. Endothelin increased murine cardiomyocyte hypertrophy in vitro, which could be blocked by estradiol and an ERβ agonist. We conclude that a functional ERβ is essential for inducing adaptive p38 and extracellular signal-regulated kinase signaling, while reducing maladaptive calcineurin signaling in normotensive deoxycorticosterone acetate female mice. Our findings address the possibility of sex-specific cardiovascular therapies.

Reactive oxygen species and proinflammatory cytokines contribute to cardiovascular diseases. Inhibition of downstream transcription factors and gene modifiers of these components are key mediators of hypertensive response. Histone acetylases/deacetylases can modulate the gene expression of these hypertrophic and hypertensive components. Therefore, we hypothesized that long-term inhibition of histone deacetylase with valproic acid might attenuate hypertrophic and hypertensive responses by modulating reactive oxygen species and proinflammatory cytokines in SHR rats. Seven-week-old SHR and WKY rats were used in this study. Following baseline blood pressure measurement, rats were administered valproic acid in drinking water (0.71% wt/vol) or vehicle, with pressure measured weekly thereafter. Another set of rats were treated with hydralazine (25 mg/kg per day orally) to determine the pressure-independent effects of HDAC inhibition on hypertension. Following 20 weeks of treatment, heart function was measured using echocardiography, rats were euthanized, and heart tissue was collected for measurement of total reactive oxygen species, as well as proinflammatory cytokine, cardiac hypertrophic, and oxidative stress gene and protein expressions. Blood pressure, proinflammatory cytokines, hypertrophic markers, and reactive oxygen species were increased in SHR versus WKY rats. These changes were decreased in valproic acid-treated SHR rats, whereas hydralazine treatment only reduced blood pressure. These data indicate that long-term histone deacetylase inhibition, independent of the blood pressure response, reduces hypertrophic, proinflammatory, and hypertensive responses by decreasing reactive oxygen species and angiotensin II type1 receptor expression in the heart, demonstrating the importance of uncontrolled histone deacetylase activity in hypertension.

Angiotensin II is a potent growth factor involved in arterial wall homeostasis. In resistance arteries, chronic increases in blood flow induce a rise in diameter associated with arterial wall hypertrophy. Nevertheless, the role of angiotensin II in this remodeling is unknown. We investigated the effect of blocking angiotensin II production or receptor activation on flow-induced remodeling of mesenteric resistance arteries. Arteries were ligated in vivo to generate high-flow arteries compared with normal flow (control) vessels located at a distance. Arteries were isolated after 1 week for in vitro analysis. Arterial diameter, media surface, endothelial NO synthase expression, superoxide production, and extracellular signal-regulated kinase 1/2 phosphorylation were higher in high-flow than in control arteries. Angiotensin-converting enzyme inhibition (perindopril) and angiotensin II type 1 receptor blockade (candesartan) prevented arterial wall hypertrophy without affecting diameter enlargement. The nonselective vasodilator hydralazine had no effect on remodeling. Although perindopril and candesartan increased endothelial NO synthase expression in high-flow arteries, hypertrophy remained in rats treated with N(G)-nitro-l-arginine methyl ester and mice lacking endothelial NO synthase. Perindopril and candesartan reduced oxidative stress in high-flow arteries, but superoxide scavenging did not prevent hypertrophy. Both Tempol and the absence of endothelial NO synthase prevented the rise in diameter in high-flow vessels. Extracellular signal-regulated kinase 1/2 activation in high-flow arteries was prevented by perindopril and candesartan and not by hydralazine. Extracellular signal-regulated kinase 1/2 inhibition in vivo (U0126) prevented hypertrophy in high-flow arteries. Thus, a chronic rise in blood flow in resistance arteries induces a diameter enlargement involving NO and superoxide, whereas hypertrophy was associated with extracellular signal-regulated kinase 1/2 activation by angiotensin II.

Hypertension-induced diastolic heart failure accounts for a large proportion of all heart failure presentations. Hypertension also induces left ventricular (LV) hypertrophy. Fixed-dose isosorbide dinitrate/hydralazine (HISDN) decreased mortality in human systolic heart failure but it is unknown whether it improves maladaptive myocardial remodeling. We sought to test the hypothesis that chronic HISDN modulates LV hypertrophy and myocardial remodeling in hypertension-induced diastolic heart failure. FVB mice underwent either saline (n=18) or aldosterone (n=28) infusion. All underwent uninephrectomy and drank 1% salt water for 4 weeks. Mice were randomized after surgery to regular chow or chow containing HISDN (isosorbide dinitrate: 26 mg/kg per day; hydralazine: 50 mg/kg per day) for 4 weeks. Aldosterone infusion increased tail-cuff blood pressure (161+/-3 mm Hg) versus saline-infused mice (129+/-2 mm Hg). Aldosterone induced LV hypertrophy versus saline-infused mice (LV:body weight ratio: 4.2+/-0.1 versus 3.6+/-0.1 mg/g). HISDN attenuated the aldosterone-induced increased in systolic blood pressure (137+/-5 mm Hg) and also lowered blood pressure in saline-infused mice (114+/-2 mm Hg). However, HISDN did not cause LV hypertrophy regression in aldosterone-infused mice. Aldosterone increased LV end-diastolic dimensions that were not attenuated by HISDN. Similarly, neither aldosterone infusion nor HISDN affected LV end-systolic dimensions. LV ejection fraction and wet:dry lung ratio were not different between aldosterone-untreated and aldosterone-HISDN mice. However, mitral Doppler E/A ratio (a measure of diastolic function), exercise capacity, and plasma soluble vascular cell adhesion molecule 1 levels were improved in aldosterone-HISDN hearts. In conclusion, fixed-dose HISDN improved hypertension, diastolic function, and exercise capacity and reduced soluble vascular cell adhesion molecule 1 levels. There were no reductions in LV hypertrophy, cardiac fibrosis, or pulmonary congestion. These functional improvements are likely related to extracardiac effects, such as effects on the vasculature.

One ultimate goal of hypertension therapy is to cause permanent reversal ("regression") of already established hypertension. Our aim was to examine whether high-dose "pulse" treatment with a renin-angiotensin system inhibitor could cause regression of established hypertension and to link this action to reversal of arteriolar hypertrophy and changes in vascular matrix metalloproteinase activities. First, 16-week-old male spontaneously hypertensive rats (n=60) were pulse treated for 2 weeks with high-dose angiotensin-converting enzyme inhibitor (enalapril), angiotensin receptor blocker (candesartan), calcium channel blocker (nifedipine), or vasodilator (hydralazine) with or without salt restriction, and the long-term effects on blood pressure were examined. Second, spontaneously hypertensive rats were treated with angiotensin receptor blocker or calcium channel blocker, and the effects on renal gene expressions, arteriolar structure, and vascular matrix metalloproteinase were compared. Treatment of spontaneously hypertensive rats with different antihypertensive agents caused apparently similar reductions in blood pressure during the course of the pulse treatment, within the limitations of the tail-cuff method. After cessation of medications, blood pressure in the rats treated with renin-angiotensin system inhibitor remained reduced by >30 to 40 mm Hg for 4 months. No such effect was seen with calcium channel blocker or vasodilator. The 2-week angiotensin receptor blocker treatment induced a marked reversal of the arteriolar hypertrophy specifically in the small (30 to 100 microm) renal arterioles, together with increased expression and activity of matrix metalloproteinase-13. In conclusion, transient high-dose pulse treatment with angiotensin receptor blocker caused changes in vascular matrix metalloproteinase activity, specific reversal of renal arteriolar hypertrophy, and regression of hypertension in spontaneously hypertensive rats.

There is increasing evidence for a role of somatic cellular senescence in physiological aging but also in injury and disease. Cell cycle inhibitor p16(INK4a) is the key mediator for stress and aberrant signaling induced senescence. Here we report that elevated blood pressure markedly induced p16(INK4a) expression in rat kidneys and hearts, as well as in human kidneys. In kidneys from deoxycorticosterone acetate-salt-treated rats, p16(INK4a) induction was found in tubular, glomerular, interstitial, and vascular cells and correlated with the typical histopathologic features of hypertensive target organ damage. p16(INK4a) expression also correlated with phospho-p38, a positive upstream regulator of p16(INK4a) expression. In left ventricles, increased p16(INK4a) expression was found in myocardium and cardiac arteries. Antihypertensive medication consistent of hydrochlorothiazide, hydralazine, and reserpine ameliorated the histopathologic changes and attenuated p16(INK4a) expression in kidneys of deoxycorticosterone acetate-salt-treated rats. Nonantihypertensive administration of spironolactone also reduced kidney damage and p16(INK4a) expression. p16(INK4a) induction was further observed in kidneys from hypertensive transgenic rats heterozygous for the mouse Ren-2 gene and was prevented by the angiotensin II type 1 receptor blocker losartan. In human kidney biopsies showing hypertensive nephrosclerosis, increased p16(INK4a) expression was found compared with age-matched normotensive control subjects. Thus, hypertension induces cellular senescence via p16(INK4a), possibly through p38, thereby contributing to hypertensive target organ damage. This detrimental effect can be overcome by different therapeutic drug strategies.

We analyzed the effect of hypertension on postischemic vasculogenesis. Ischemia was induced by right femoral artery ligature in Wistar Kyoto rats (WKY) or spontaneously hypertensive rats (SHR) treated with or without angiotensin-converting enzyme inhibitor (Perindopril, 0.76 mg/kg/d) and angiotensin type 1 receptor blocker (losartan, 30 mg/kg/d). Basal postischemic neovascularization was reduced in SHR compared to WKY (P<0.05, n=8). Treatment with ACE inhibitor or angiotensin type 1 receptor blocker decreased blood pressure levels by 1.4- and 1.3-fold (P<0.001), respectively and restored vessel growth in SHR to WKY levels. Interestingly, 14 days after bone-marrow mononuclear cell (BM-MNC) transfusion, angiographic scores, capillary density, and foot perfusion were decreased by 1.4-, 1.5-, and 1.2-fold, respectively in SHR transfused with BM-MNCs isolated from SHR compared to those receiving BM-MNCs of WKY (P<0.05, n=6). Alteration in BM-MNCs proangiogenic potential was likely related to the reduction in their ability to mobilize into peripheral circulation, as revealed by the 2.9-fold decrease in number of circulating CD34+/CD117+ cells (P<0.001) and to differentiate into cells with endothelial phenotype, as revealed by the 2.1-fold reduction in percentages of DilLDL/BS-1 lectin positive cells (P<0.001). In addition, reactive oxygen species (ROS) levels were increased by 2.2-fold in SHR BM-MNCs compared to WKY BM-MNCs (P<0.01), as assessed by L-012 luminescence. Cotreatment with ACE inhibitor, angiotensin type 1 receptor blocker, or antioxidants (NAC 3 mmol/L, Apocynin 200 micromol/L) reduced ROS levels, improved the number of DilLDL/BS-1 lectin-positive cells by around 1.5-fold, and restored BM-MNCs proangiogenic effects in ischemic hindlimb. In conclusion, alteration in progenitor cell proangiogenic function may participate to the hypertension-induced impairment in postischemic revascularization.

We tested the hypothesis that female and male mice differ in terms of cardiac hypertrophy after deoxycorticosterone acetate (DOCA)+salt hypertension (uninephrectomy and 1% saline in drinking water) and focused on calcineurin signaling. We excluded confounding effects of blood pressure elevation or sex-related blood pressure differences by treating DOCA-salt mice with hydralazine (250 mg/L in drinking water). We found that directly measured mean arterial blood pressure was lowered to control values with hydralazine and corroborated this finding in separate mouse groups with radiotelemetry. Male mice were more responsive to DOCA-salt-related effects. They developed more left ventricular hypertrophy and more renal hypertrophy after 6 weeks of DOCA-salt+hydralazine compared with female mice. In hearts, transcripts for calcineurin Abeta and for myocyte-enriched calcineurin interacting protein 1 were upregulated in male but not in female mice. Enhanced activity of calcineurin Abeta, as indicated by diminished phosphorylation of NFATc2 in male mice, accounted for this sex-specific difference. Stretch-related, inflammatory, and profibrotic responses were also accentuated in male mice, as shown by higher transcript levels of atrial natriuretic peptide, monocyte chemoattractant protein-1, and transforming growth factor-beta. Our results support sex-specific regulation of the calcineurin pathway in response to largely blood pressure-independent mineralocorticoid action. We suggest that sex-specific calcineurin activation determines the maladaptive cardiac and renal hypertrophic responses and accompanying organ injury in male mice.

The aim of this study was to determine the effects of carbon monoxide (CO) at a nontoxic low concentration on the cardiac and vascular hypertrophic response and reactive oxygen species generation, compared with the action of a vasodilator, hydralazine. Twelve- to 16-week-old low-density lipoprotein receptor knockout mice were subjected to angiotensin II (Ang II) infusion using osmotic minipumps (Ang II group; n=11) for 2 weeks. Controls were administered saline (n=10). Animals were exposed to CO in a chamber at 60 ppm for 2 hours per day with or without Ang II infusion (Ang II+CO group, n=10; CO group, n=9). Hydralazine was administered with Ang II infusion (n=10). Animals exhibited elevated arterial carboxyhemoglobin after CO exposure. Although the CO exposure did not affect systolic blood pressure without Ang II infusion, the hypertensive response after Ang II infusion was significantly attenuated by CO. Accordingly, the mice in the Ang II+CO group showed lesser left ventricular hypertrophy compared with those in the Ang II group. CO treatment also attenuated aortic hypertrophy. Interestingly, these changes were accompanied by the reduction of reactive oxygen species production, p47(phox) and p67(phox) subunit expressions of reduced nicotinamide-adenine dinucleotide phosphate oxidase, and Akt phosphorylation. Although hydralazine showed stronger antihypertensive action, superior inhibition on cardiac hypertrophy was obtained by CO (P<0.05). Furthermore, Ang II-dependent myocardial reactive oxygen species generation was more effectively suppressed by CO. Low-dose exogenous CO treatment attenuates Ang II-dependent reactive oxygen species generation, suggesting that appropriate CO administration alleviates hypertension and reduces organ hypertrophy mediated by Ang II.

The role of angiotensin II type 2 receptors (AT2Rs) remains a matter of controversy. Its vasodilatory and antitrophic properties are well accepted. Nevertheless, in hypertensive rats, AT2R stimulation induces a vasoconstriction counteracting flow-mediated dilation (FMD). This contraction is reversed by hydralazine. Because FMD is also decreased in aging, another risk factor for cardiovascular diseases, we hypothesized that AT2R function might be altered in old-rat resistance arteries. Mesenteric resistance arteries (250 mum in diameter) were isolated from old (24 months) and control (4 months) rats receiving hydralazine (16 mg/kg per day; 2 weeks) or water. FMD, NO-mediated dilation, and endothelial NO synthase expression were lower in old versus control rats. AT2R blockade improved FMD in old rats, suggesting that AT2R stimulation produced vasoconstriction. AT2R expression was higher in old rats and mainly located in the smooth muscle layer. In old rats, AT2R stimulation induced endothelium-independent contraction, which was suppressed by the antioxidant Tempol. Reactive oxygen species level was higher in old-rat arteries than in controls. Hydralazine improved FMD and NO-dependent dilation in old rats without change in AT2R expression and location. In old rats treated with hydralazine, reactive oxygen species level was reduced in endothelial and smooth muscle cells, and AT2R-dependent contraction was abolished. Thus, AT2R stimulation induced vasoconstriction through activation of reactive oxygen species production, contributing to decrease FMD in old-rat resistance arteries. Hydralazine suppressed AT2R-dependent reactive oxygen species production and AT2R-dependent contraction, improving FMD. Importantly, endothelial alterations in aging were reversible. These findings are important to consider in the choice of vasoactive drugs in aging.

Accumulating evidence suggests that mineralocorticoid receptor blockade effectively reduces proteinuria in hypertensive patients. However, the mechanism of the antiproteinuric effect remains elusive. In this study, we investigated the effects of aldosterone on podocyte, a key player of the glomerular filtration barrier. Uninephrectomized rats were continuously infused with aldosterone and fed a high-salt diet. Aldosterone induced proteinuria progressively, associated with blood pressure elevation. Notably, gene expressions of podocyte-associated molecules nephrin and podocin were markedly decreased in aldosterone-infused rats at 2 weeks, with a gradual decrease thereafter. Immunohistochemical studies and electron microscopy confirmed the podocyte damage. Podocyte injury was accompanied by renal reduced nicotinamide-adenine dinucleotide phosphate oxidase activation, increased oxidative stress, and enhanced expression of aldosterone effector kinase Sgk1. Treatment with eplerenone, a selective aldosterone receptor blocker, almost completely prevented podocyte damage and proteinuria, with normalization of elevated reduced nicotinamide-adenine dinucleotide phosphate oxidase activity. In addition, proteinuria, podocyte damage, and Sgk1 upregulation were significantly alleviated by tempol, a membrane-permeable superoxide dismutase, suggesting the pathogenic role of oxidative stress. Although hydralazine treatment almost normalized blood pressure, it failed to improve proteinuria and podocyte damage. In cultured podocytes with consistent expression of mineralocorticoid receptor, aldosterone stimulated membrane translocation of reduced nicotinamide-adenine dinucleotide phosphate oxidase cytosolic components and oxidative stress generation in podocytes. Furthermore, aldosterone enhanced the expression of Sgk1, which was inhibited by mineralocorticoid receptor antagonist and tempol. In conclusion, podocytes are injured at the early stage in aldosterone-infused rats, resulting in the occurrence of proteinuria. Aldosterone can directly modulate podocyte function, possibly through the induction of oxidative stress and Sgk1.

Recent clinical studies implicate proteinuria as a key prognostic factor for renal and cardiovascular complications in hypertensives. The pathogenesis of proteinuria in hypertension is, however, poorly elucidated. Podocytes constitute the final filtration barrier in the glomerulus, and their dysfunction may play a pivotal role in proteinuria. In the present study, we examined the involvement of podocyte injury in Dahl salt-hypertensive rats, an animal model prone to hypertensive glomerulosclerosis, and explored the effects of inhibition of aldosterone. Four-week-old Dahl salt-resistant and salt-sensitive rats were fed a 0.3% or 8.0% NaCl diet. Some salt-loaded Dahl salt-sensitive rats were treated with a selective aldosterone blocker eplerenone (1.25 mg/g diet) or hydralazine (0.5 mmol/L). After 6 weeks, salt-loaded Dahl salt-sensitive rats developed severe hypertension, proteinuria, and glomerulosclerosis. Immunostaining for nephrin, a constituent of slit diaphragm, was attenuated, whereas expressions of damaged podocyte markers desmin and B7-1 were upregulated in the glomeruli of salt-loaded Dahl salt-sensitive rats. Electron microscopic analysis revealed podocyte foot process effacement. Podocytes were already impaired at as early as 2 weeks of salt loading in Dahl salt-sensitive rats, when proteinuria was modestly increased. Both eplerenone and hydralazine partially reduced systemic blood pressure as measured by indirect and direct methods in salt-loaded Dahl salt-sensitive rats, but only eplerenone dramatically improved podocyte damage and retarded the progression of proteinuria and glomerulosclerosis. Our findings suggest that podocyte injury underlies the glomerulopathy of Dahl salt-hypertensive rats and that inhibition of aldosterone by eplerenone is protective against podocyte damage, proteinuria, and glomerulosclerosis in this hypertensive model.

Angiotensin II plays an important role in vascular remodeling through effects that involve, in part, interactions of vascular smooth muscle cells with extracellular matrix via integrins, which belong to a family of transmembrane receptors. We hypothesized that angiotensin (Ang) II regulates expression of vascular integrins and their ligands in experimental hypertension. Rats were infused subcutaneously with Ang II and received angiotensin type-1 (AT1) receptor blocker losartan, the AT1/angiotensin type-2 (AT2) [Sar1-Ile8]-Ang II, or the vasodilator hydralazine for 7 days. Osteopontin and integrin subunit expression were evaluated immunohistochemically. Ang II enhanced vascular alpha8, beta1, beta3 integrins and osteopontin expression, which were significantly reduced by losartan, [Sar1-Ile8]-Ang II, and hydralazine. Although Ang II increased vascular alpha5 subunit expression, this was additionally increased by losartan. Losartan was the only treatment that induced alpha1 subunit expression. These results demonstrate that AT1 and AT2 receptors have countervailing effects on vascular integrin subunit expression that may influence their effects on vascular remodeling and extracellular matrix composition.

We investigated the role of angiotensin II type 1 (AT1) and AT2 receptors, matrix metalloproteinases (MMPs), and extracellular matrix (ECM) components involved in vascular remodeling of resistance arteries induced by angiotensin II (Ang II). Sprague-Dawley rats received Ang II (120 ng/kg per minute SC) +/- the AT1 antagonist losartan (10 mg/kg per day PO), the AT1/AT2 antagonist Sar1-Ile8-Ang II (Sar-Ile; 10 microg/kg per minute SC), or hydralazine (25 mg/kg per day PO) for 7 days. Structure and mechanical properties of small mesenteric arteries were evaluated on a pressurized myograph. Ang II increased growth index (+21%), which was partially decreased by losartan (-11%) and abrogated by Sar-Ile. Hydralazine markedly increased growth index (+32%) despite systolic blood pressure (BP) lowering, suggesting a BP-independent effect of Ang II on vascular growth. Elastic modulus was increased by Sar-Ile compared with Ang II and control. Vascular type I collagen was reduced (P<0.05), whereas fibronectin increased significantly with Sar-Ile. Vascular tissue inhibitor of metalloproteinase-2 binding to MMP-2 was abrogated by Sar-Ile, but MMP-2 activity was significantly increased compared with losartan, Ang II, and controls. Thus, AT1 blockade exerted antigrowth effects and reduced stiffness of small resistance arteries by decreasing nonelastic fibrillar components (collagen and fibronectin). Concomitant AT1/AT2 blockade prevented growth, reduced collagen type I and elastin deposition but increased vascular stiffness, fibronectin, and MMP-2 activity. These results demonstrate opposing roles of AT1 receptors that increase fibronectin and vascular stiffness and AT2 receptors that decrease MMP-2 and increase elastin. Changes in vascular wall mechanics, ECM deposition, and MMP activity are thus modulated differentially by Ang II receptors.

Although plasma levels of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are elevated early after myocardial infarction (MI), the significance is not fully understood. We therefore investigated the function of natriuretic peptides after induction of MI in knockout (KO) mice lacking the natriuretic peptide receptor guanylyl cyclase-A, the receptor for ANP and BNP. KO and wild-type (WT) mice were subjected to left coronary artery ligation and then followed up for 4 weeks. Irrespective of genotype, almost all deaths occurred within 1 week after induction of MI. KO mice showed significantly higher mortality because of a higher incidence of acute heart failure, which was associated with diminished water and sodium excretion and with higher cardiac levels of mRNAs encoding ANP, BNP, transforming growth factor-beta1, and type I collagen. By 4 weeks after infarction, left ventricular remodeling, including myocardial hypertrophy and fibrosis, and impairment of left ventricular systolic function were significantly more severe in KO than WT mice. Notably, the enhanced myocardial fibrosis seen in KO mice was virtually absent in infarcted double-KO mice, lacking guanylyl cyclase-A and angiotensin II type 1a receptors, although there was no improvement in survival and no attenuation of cardiac hypertrophy. Thus, guanylyl cyclase-A activation by endogenous cardiac natriuretic peptides protects against acute heart failure and attenuates chronic cardiac remodeling after MI. These beneficial effects are mediated partly through inhibition of the renin-angiotensin system (RAS), although RAS-independent protective actions of guanylyl cyclase-A are also suggested.

Although Mg2+ contributes to blood pressure regulation partly in terms of vasodilator action, its sympatholytic effect may also play an important role to control blood pressure. Thus, in the present study, we investigated the effect of Mg2+ on sympathetic tone and blood pressure. We studied its actions on the blood pressure response to hydralazine, a direct vasodilator, in conscious spontaneously hypertensive rats (SHRs), and to electrical stimulation in the pithed Sprague-Dawley rat; catecholamine release by peripheral sympathetic nerve endings; and the N-type Ca2+ channels of cultured neural cells. Intravenous Mg2+ infusion (MgSO4: 3x10(-6) mol/kg body weight/min) induced the greater hypotensive response to hydralazine with attenuated reflex tachycardia in SHRs. In pithed rats, Mg2+ infusion significantly attenuated the blood pressure elevation (2+/-2 mm Hg versus 27+/-6 mm Hg, P<0.01) in response to spinal electrical stimulation. In the perfused mesenteric arteries system, norepinephrine release was significantly attenuated (51+/-2%, P<0.01) by high Mg2+ concentration solution (4.8 mmol/L) compared with normal Mg2+ solution (1.2 mmol/L). When we applied the perforated whole-cell patch clamp method to nerve growth factor-treated PC12 cells, Mg2+ blocked voltage-gated Ca2+ currents in a concentration-dependent manner. The majority of the voltage-gated Ca2+ currents were carried through N-type channels, followed by L-type channels. Mg2+ blocked both of these channels. These findings suggest that Mg2+ blocks mainly N-type Ca2+ channels at nerve endings, and thus inhibits norepinephrine release, which decreases blood pressure independent of its direct vasodilating action.

Central nervous system mechanisms are involved in hypertension caused by chronic inhibition of nitric oxide (NO) synthesis. Chronic inhibition of NO synthesis might also activate the Rho/Rho-kinase pathway in the vasculature. We recently demonstrated that activation of the Rho/Rho-kinase pathway in the nucleus tractus solitarii (NTS) contributes to hypertensive mechanisms in spontaneously hypertensive rats. The aim of the present study was to determine whether activation of this pathway also contributes to neurogenic hypertensive mechanisms caused by chronic NO synthesis inhibition. The NO synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) was administered to Wistar-Kyoto rats in their drinking water (1 mg/mL) for 2 weeks. Bilateral microinjection of Y-27632, a specific Rho-kinase inhibitor, into the NTS elicited decreases in arterial pressure, heart rate, and renal sympathetic nerve activity in control rats and L-NAME-treated rats. The magnitude of the decrease, however, was significantly greater in L-NAME-treated than in control rats. In another group of rats, the specific Rho-kinase inhibitor, Y-27632, was administered intracisternally for 2 weeks with a mini-osmotic pump from the beginning of treatment with L-NAME. Y-27632 co-treatment significantly attenuated the increase in arterial pressure. Furthermore, the expression level of membranous RhoA and phosphorylation of the target proteins of Rho-kinase, the ERM (ezrin, radixin, moesin) family members, was significantly greater in L-NAME-treated rats than in control rats. These results indicate that activation of the Rho/Rho-kinase pathway in the NTS contributes to neurogenic hypertension caused by chronic NO synthase inhibition.

Endothelin A (ETA) receptor blockade has prevented vascular remodeling in aldosterone and salt-induced hypertension. To evaluate effects of the ETA receptor antagonist, BMS 182874, compared with the aldosterone antagonist, spironolactone, on vascular remodeling in aldosterone-infused rats not exposed to a high salt diet, Sprague-Dawley rats were infused subcutaneously with aldosterone (0.75 microg/h) and treated with BMS 182874 (40 mg. kg-1. d-1), spironolactone, or hydralazine (both 25 mg. kg-1. d-1) while receiving a normal salt diet for 6 weeks. Aldosterone increased systolic BP (P<0.01), plasma endothelin (3.33+/-0.32 versus 1.85+/-0.40 pmol/L in control, P<0.05), systemic oxidative stress as shown by plasma thiobarbituric acid-reacting substances and vascular nicotinamide adenine dinucleotide phosphate (NADPH) activity. Aldosterone increased small artery media thickness (17.7+/-0.9 versus 13.6+/-0.8 microm in control, P<0.05) and media/lumen ratio (7.6+/-0.4 versus 5.5+/-0.4% in control, P<0.05), with growth index of 21% indicating hypertrophic remodeling. Laser confocal microscopy showed increased collagen and fibronectin deposition and intercellular adhesion molecule-1 (ICAM-1) content in the vessel wall of aldosterone-infused rats. The 3 treatments lowered BP, although hydralazine was slightly less effective. BMS 182874 and spironolactone decreased oxidative stress, normalized the hypertrophic remodeling, decreased collagen and fibronectin deposition, and reduced ICAM-1 abundance in the vascular wall of aldosterone-infused rats, whereas hydralazine only reduced NADPH activity in aorta but did not affect the remaining parameters. Vascular remodeling of small arteries occurs in aldosterone-infused rats exposed to a normal salt diet and may be mediated in part by ET-1 via stimulation of ETA receptors. Endothelin blockade may exert beneficial effects on vascular remodeling, fibrosis, oxidative stress, and adhesion molecule expression in aldosterone-induced hypertension.

Essential hypertension is a common disorder, associated with increased endothelin-1-mediated vasoconstrictor tone at rest. We hypothesized that increased vasoconstrictor activity of endothelin-1 might explain why the normal decrease in peripheral vascular resistance in response to exercise is attenuated in hypertensive patients. Therefore, we investigated the effect of endothelin A (ET(A)) receptor blockade on the vasodilator response to handgrip exercise. Forearm blood flow responses to handgrip exercise (15%, 30%, and 45% of maximum voluntary contraction) were assessed in hypertensive patients and matched normotensive subjects, before and after intra-arterial infusions of the ET(A) receptor antagonist BQ-123; a control dilator, hydralazine; and placebo (saline). Preinfusion (baseline) vasodilation in response to exercise was significantly attenuated at each workload in hypertensive patients compared with normotensive subjects. Intra-arterial infusions of hydralazine and saline did not increase the vasodilator response to exercise in either hypertensives or normotensives at any workload. The vasodilator response to exercise was markedly enhanced after BQ-123 at the 2 higher workloads in hypertensives (157+/-48%, P<0.01; 203+/-58%, P<0.01) but not in normotensives. This suggests that the impaired vasodilator response to exercise in hypertensive patients is, at least in part, a functional limitation caused by endogenous ET(A) receptor-mediated vasoconstriction. Treatment with endothelin receptor antagonists may, therefore, increase exercise capacity in essential hypertension.

Chronic inhibition of endothelial NO synthesis by the administration of N(G)-nitro-L-arginine methyl ester (L-NAME) to rats induces early vascular inflammation (monocyte infiltration into coronary vessels and monocyte chemoattractant protein-1 expression) as well as subsequent arteriosclerosis. The small GTPase Rho controls cell adhesion, motility, and proliferation and is activated by several growth factors such as angiotensin II. We investigated the effect of a specific inhibitor of Rho-kinase, Y-27632, in rats treated with L-NAME to determine the role of the Rho/Rho-kinase pathway in the development of arteriosclerosis. We found here increased activity of Rho/Rho-kinase after L-NAME administration and its prevention by angiotensin II type 1 receptor blockade. Hydralazine or lecithinized superoxide dismutase (l-SOD) did not affect Rho/Rho-kinase activity. Co-treatment with Y-27632 did not affect the L-NAME-induced increase in cardiovascular tissue ACE activity or L-NAME-induced decrease in plasma NO concentrations, but did prevent the L-NAME-induced early inflammation and late coronary arteriosclerosis. In addition, Y-27632 prevented the increased gene expression of monocyte chemoattractant protein-1 and transforming growth factor-beta1 as well as cardiac fibrosis and glomerulosclerosis. These findings suggest that increased activity of Rho/Rho-kinase pathway mediated via the angiotensin II type 1 receptor may thus be important in the pathogenesis of early vascular inflammation and late remodeling induced by chronic inhibition of NO synthesis. The beneficial effects of Rho-kinase inhibition are not mediated by restoration of NO production. The Rho-kinase pathway could be a new therapeutic target for treatment of vascular diseases.

Cardiac vagal control has prognostic significance in cardiac disease, but the control mechanisms of this system remain poorly understood. We have previously demonstrated a role for NO in promoting vagal control of heart rate in humans. Here we examine the influence of L-arginine, the substrate for NO synthase, on this mechanism in healthy human subjects. Eleven healthy volunteers (9 men; age, 20 to 25 years) underwent measurement of heart rate variability and baroreflex sensitivity before and during a systemic infusion of L-arginine (1 g/min; total, 30 g). To control for the fall in blood pressure, comparison was made with an infusion of the control vasodilator hydralazine. Stereospecificity of observed effects was investigated by infusion of D-arginine. Urinary nitrate and nitrite (NO(x)) and cGMP concentrations were measured as indexes of NO generation. L-Arginine infusion produced a drop in mean arterial pressure of 5 mm Hg. This fall in blood pressure was matched by hydralazine infusion and was not observed with either D-arginine or saline infusion. Although RR interval duration, heart rate variability, and baroreflex sensitivity all fell significantly with hydralazine, the same degree of baroreflex unloading with L-arginine produced an increase in RR interval duration and no change or even slight increases in heart rate variability and baroreflex sensitivity. In contrast, D-arginine produced falls in high-frequency indexes of heart rate variability compared with saline. Only L-arginine increased urinary NO(x) and cGMP excretion. In conclusion, these data demonstrate that short-term L-arginine infusion facilitates vagal control of heart rate in healthy humans, probably via increased NO synthesis.

We previously reported the generation of transgenic mice containing the entire human renin gene with a 900-bp promoter. To determine whether all the required elements for angiotensin II-mediated suppression of human renin are present in these mice, angiotensin II was chronically infused by means of osmotic minipump at both low and high doses, 200 and 1000 ng/kg per minute, respectively. Blood pressure was measured by tail-cuff, and kidney renin mRNA levels were quantitated using ribonuclease protection assays. Blood pressure was unchanged in mice receiving either vehicle or low-dose angiotensin II infusion but was increased by approximately 40 mm Hg with the higher dose of angiotensin II. Mouse renin mRNA decreased by >60% during both pressor and nonpressor angiotensin II infusion. Human renin mRNA was not suppressed by nonpressor angiotensin II and was paradoxically increased 1.9-fold by pressor angiotensin II. The lack of upregulation during nonpressor angiotensin II suggested that the increase might be pressure-mediated. To test this, the angiotensin II-induced increase in blood pressure was prevented by coadministration of the vasodilator, hydralazine (15 mg/kg per day). Hydralazine alone decreased blood pressure (-27+/-3 mm Hg) and increased mouse renin mRNA 2.4-fold. Human renin mRNA was unresponsive to this vasodilator-induced fall in pressure and despite the normalization of blood pressure by hydralazine, high-dose angiotensin II still caused a 2.1-fold increase in human renin mRNA. Thus, the first 900 bp of the human renin promoter does not contain all the elements required for appropriate angiotensin II-mediated suppression of human renin mRNA.

Cardiac autonomic control is of prognostic significance in cardiac disease, yet the control mechanisms of this system remain poorly defined. Animal data suggest that nitric oxide (NO) modulates cardiac autonomic control. We investigated the influence of NO on the baroreflex control of heart rate in healthy human subjects. In 26 healthy male volunteers (mean age, 23+/-5 years), we measured heart rate variability and baroreflex sensitivity during inhibition of endogenous NO production with N(G)-monomethyl-L-arginine (L-NMMA) (3 mg/kg per hour) and during exogenous NO donation with sodium nitroprusside (1 to 3 mg/h). Increases from baseline (Delta) in high-frequency (HF) indexes of heart rate variability were smaller with L-NMMA in comparison to an equipressor dose of the control vasoconstrictor phenylephrine (12 to 42 microg/kg per hour): Deltaroot mean square of successive RR interval differences (DeltaRMSSD)=23+/-32 versus 51+/-48 ms (P<0.002); Deltapercentage of successive RR interval differences >50 ms (DeltapNN50)=5+/-15% versus 14+/-12% (P<0.05); and DeltaHF normalized power=-2+/-7 versus 9+/-8 normalized units (P<0.01), respectively. Relative preservation of these indexes was observed during unloading of the baroreflex with sodium nitroprusside compared with a matched fall in blood pressure produced by a control vasodilator, hydralazine (9 to 18 mg/h): DeltaRMSSD=-8+/-8 versus -24+/-15 ms (P<0.001); DeltapNN50=-6+/-11% versus -15+/-19% (P<0.01); DeltaHF normalized power=-7+/-13 versus -13+/-11 normalized units (P<0.05), respectively. The change in cross-spectral alpha-index calculated as the square root of the ratio of RR interval power to systolic spectral power in the HF band (although not alpha-index calculated in the same way for the low-frequency bands or baroreflex sensitivity assessed by the phenylephrine bolus method) was attenuated with L-NMMA compared with phenylephrine (Delta=4+/-8 versus 14+/-15 ms/mm Hg, respectively; P<0.02) and with sodium nitroprusside compared with hydralazine (Delta=-7+/-6 and -9+/-7 ms/mm Hg, respectively; P<0.05). In conclusion, these data demonstrate that NO augments cardiac vagal control in humans.

Reports on the effectiveness of endothelin receptor blockers in angiotensin (Ang) II-induced end-organ damage are conflicting, and the mechanisms involved are uncertain. We tested the hypothesis that endothelin (ET)(A/B) receptor blockade with bosentan (100 mg/kg by gavage after age 4 weeks) ameliorates cardiac and renal damage by decreasing inflammation in rats harboring both human renin and angiotensinogen genes (dTGR). Furthermore, we elucidated the effect of bosentan on tissue factor (TF), which is a key regulator of the extrinsic coagulation cascade. We compared bosentan with hydralazine (80 mg/L in the drinking water for 3 weeks) as a blood pressure control. Untreated dTGR featured hypertension, focal necrosis in heart and kidney, and a 45% mortality rate (9 of 20) at age 7 weeks. Compared with Sprague-Dawley controls, both systolic blood pressure and 24-hour albuminuria were increased in untreated dTGR (203+/-8 versus 111+/-2 mm Hg and 67.1+/-8.6 versus 0.3+/-0.06 mg/d at week 7, respectively). Bosentan and hydralazine both reduced blood pressure and cardiac hypertrophy. Mortality rate was markedly reduced by bosentan (1/15) and partially by hydralazine (4/15). However, only bosentan decreased albuminuria and renal injury. Untreated and hydralazine-treated dTGR showed increased nuclear factor (NF)-kappaB and AP-1 expression in the kidney and heart; the p65 NF-kappaB subunit was increased in the endothelium, vascular smooth muscles cells, infiltrating cells, glomeruli, and tubules. In the heart and kidney, ET(A/B) receptor blockade inhibited NF-kappaB and AP-1 activation compared with hydralazine treatment. Macrophage infiltration, ICAM-1 expression, and the integrin expression on infiltrating cells were markedly reduced. Renal vasculopathy was accompanied by increased tissue factor expression on macrophages and vessels of untreated and hydralazine-treated dTGR, which was markedly reduced by bosentan. Thus, ET(A/B) receptor blockade inhibits NF-kappaB and AP-1 activation and the NF-kappaB- and/or AP-1-regulated genes ICAM-1, VCAM-1, and TF, independent of blood pressure-related effects. We conclude that Ang II-induced NF-kappaB and AP-1 activation and subsequent inflammation and coagulation involve at least in part the ET(A/B) receptors.

In this study, we investigated the regulation and physiological role of heme oxygenase-1 (HO-1) in the kidney of rats with hypertension. Rats were continuously administered either angiotensin II (Ang II) or norepinephrine with an osmotic minipump for up to 7 days. Ang II infusion decreased the glomerular filtration rate (GFR) as determined through creatinine clearance (3.2+/-0.2 versus 1.2+/-0.2 mL/min with Ang II infusion, P<0.01) and increased proteinuria (9. 7+/-1.3 versus 28.1+/-7.2 mg/d with Ang II infusion, P<0.01). In contrast, norepinephrine did not alter these laboratory values. Ang II infusion significantly increased HO-1 expression in mRNA (442+/-98% of control at day 5, P<0.01) and protein levels (314+/-49% of control at day 5, P<0.01). Immunohistochemistry showed that in the kidney of normotensive rats, HO-1 was expressed mainly in the basal side in the renal tubules. After Ang II infusion, HO-1 staining was more extensively dispersed in the tubular epithelial cells. The intraperitoneal administration of zinc protoporphyrin, an HO inhibitor, to Ang II-infused rats further decreased GFR (0.8+/-0. 1 mL/min) and increased proteinuria (52.5+/-13.0 mg/d). In contrast, the administration of hemin, an HO inducer, ameliorated the Ang II-induced decrease in GFR (2.4+/-0.2 mL/min) and increase in proteinuria (9.3+/-4.5 mg/d). These data suggest that HO-1 upregulation in the kidney of Ang II-induced hypertensive rats may exert a renoprotective effect against Ang II-induced renal injury.

Through the use of microanatomic techniques, we investigated the effects of treatment with some dihydropyridine-type calcium antagonists (CAs) (ie, lercanidipine, manidipine, and nicardipine) and with the nondihydropyridine-type vasodilator hydralazine on hypertension-dependent glomerular injury and on the morphology of afferent and efferent arterioles in spontaneously hypertensive rats (SHR). Fourteen-week-old male SHR and age-matched normotensive Wistar-Kyoto rats were left untreated (control groups). Four additional groups of 14-week-old SHR were treated for 12 weeks with daily oral doses of 2.5 mg/kg lercanidipine, 5 mg/kg manidipine, 3 mg/kg nicardipine, or 10 mg/kg hydralazine. These treatments decreased systolic blood pressure values to a similar extent in SHR. Signs of glomerular injury, as characterized by glomerulosclerosis, hypertrophy, and an increased number of mesangial cells, were observed in control SHR. The treatment with CAs improved glomerular morphology and decreased the number of mesangial cells. Lercanidipine and manidipine were more effective than nicardipine in countering glomerular injury. In the SHR, both afferent and efferent arterioles revealed luminal narrowing, accompanied by increased wall thickness in efferent arterioles. The dihydropyridine-type derivatives that were tested decreased the luminal narrowing of afferent arterioles. Lercanidipine and manidipine countered the luminal narrowing of efferent arterioles. Hydralazine had no effect on hypertension-dependent glomerular injury or vascular changes. The present data indicate that lercanidipine and manidipine vasodilate afferent and efferent arterioles in SHR. A vasodilatory activity on efferent arteriole, which is not induced by the majority of CAs, may represent an useful property in the treatment of hypertension complicated by renal disease.

The blood pressure-independent effects of angiotensin II (Ang II) were examined in double transgenic rats (dTGR) harboring human renin and human angiotensinogen genes, in which the end-organ damage is due to the human components of the renin angiotensin system. Triple-drug therapy (hydralazine 80 mg/L, reserpine 5 mg/L, and hydrochlorothiazide 25 mg/L in drinking water) was started immediately after weaning. Triple-drug therapy normalized blood pressure and coronary resistance, only partially prevented cardiac hypertrophy, and had no effect on ratio of renal weight to body weight. Although triple-drug therapy delayed the onset of renal damage, severe albuminuria nevertheless occurred. Semiquantitative scoring of ED-1-positive and MIB-5-positive (nuclear cell proliferation-associated antigen Ki-67) cells showed profound perivascular monocyte/macrophage infiltration and cell proliferation in kidneys and hearts of untreated dTGR. Triple-drug therapy had only a minimal effect on local inflammatory response or vascular cell proliferation. In contrast, a novel orally active human renin inhibitor (HRI), 30 mg/kg by gavage for 4 weeks, normalized blood pressure and coronary resistance and also prevented cardiac hypertrophy and albuminuria. ED-1-positive cells and MIB-5-positive cells were decreased by HRI in hearts and kidneys almost to levels observed in normotensive Sprague-Dawley rats. The renoprotective effects of HRI were at least in part due to improved renal hemodynamics and distal tubular function, since HRI shifted renal pressure-diuresis/natriuresis curves leftward by approximately 35 mm Hg, increased glomerular filtration rate and renal blood flow, and shifted the fractional water and sodium excretion curves leftward. In untreated dTGR, plasma Ang II was increased by 400% and renal Ang II level was increased by 300% compared with Sprague-Dawley rats. HRI decreased plasma human renin activity by 95% and normalized Ang II levels in both plasma and kidney compared with triple-drug therapy. Our findings indicate that in dTGR harboring human renin and angiotensinogen genes, Ang II causes end-organ damage and promotes inflammatory response and cellular growth largely independent of blood pressure.

Angiotensin II (Ang II) plays an important role in cardiac remodeling through stimulation of proliferation and extracellular matrix (ECM) production in cardiac fibroblasts. Integrins are a family of transmembrane receptors that mediate the attachment of cells to ECM. We hypothesized that Ang II regulation of integrins further contributes to its role in cardiac remodeling. We cultured adult rat cardiac fibroblasts with and without Ang II (100 nmol/L) to determine the effects on mRNA and protein levels of integrins, as well as alpha-actinin and other cytoskeletal proteins that link to integrins at the site of focal adhesions. Ang II was also added in the presence of irbesartan (10 micromol/L), a specific Ang II type 1 (AT(1)) receptor antagonist, or PD 123319 (10 micromol/L), a specific Ang II type 2 receptor antagonist. To investigate the function of these integrins, we determined the effects of blocking antibodies on Ang II-induced adhesion to ECM. We also treated spontaneously hypertensive rats (SHR) with an AT(1) receptor blocker, losartan, or with hydralazine to investigate integrin and alpha-actinin expression in treated and untreated SHR. Ang II enhanced alpha(v), beta(1), beta(3), and beta(5) integrins; osteopontin; and alpha-actinin mRNA and protein levels in cardiac fibroblasts. All of these effects were inhibited by irbesartan but not by PD 123319. Pretreatment of cardiac fibroblasts with Ang II enhanced cell attachment to ECM proteins and induced focal adhesion kinase phosphorylation. Blocking antibodies to beta(3) and alpha(v)beta(5) attenuated Ang II-induced adhesion. In SHR, ventricular alpha(v) and beta(5) integrin expression and alpha-actinin were increased compared with those in Wistar-Kyoto rats. Although both losartan and hydralazine lowered mean arterial pressure and decreased peripheral vascular resistance, only losartan attenuated the increased integrin, alpha-actinin, fibronectin laminin, and osteopontin expression and the increased left ventricular mass (as determined with echocardiography). Hydralzine had none of these effects. Although both agents attenuated beta-myosin heavy chain expression, a marker of hypertrophy, losartan had a greater effect. These results suggest that integrins and alpha-actinin are upregulated by Ang II and in left ventricular hypertrophy and that the block of expression of these proteins through inhibition of the AT(1) receptor is associated with attenuation of the hypertrophic response. Ang II induces integrin and alpha-actinin expression in cardiac fibroblasts that is associated with adhesion and left ventricular hypertrophy and blocked through inhibition of the AT(1) receptor.

We previously reported that increased apoptosis participates in the regression of aortic hypertrophy in spontaneously hypertensive rats. To further document the potential role of apoptosis in cardiovascular therapy, we examined apoptosis during regression of hypertrophy in the heart of spontaneously hypertensive rats receiving the antihypertensive drug enalapril (30 mg. kg(-1). d(-1)), losartan (30 mg. kg(-1). d(-1)), nifedipine (35 mg. kg(-1). d(-1)), hydralazine (40 mg. kg(-1). d(-1)), propranolol (50 mg. kg(-1). d(-1)), or hydrochlorothiazide (75 mg. kg(-1). d(-1)) for 1 to 4 weeks, starting at 10 to 11 weeks of age. Systolic blood pressure and heart rate were measured by the tail-cuff method. Markers of apoptosis included oligonucleosomal DNA fragmentation in extracted cardiac DNA or in situ in ventricular cross sections labeled with terminal deoxynucleotidyl transferase. Cardiac DNA synthesis was evaluated by [(3)H]-thymidine incorporation in vivo. All drugs reduced cardiac workload, defined as the product of blood pressure and heart rate, by >20% at 4 weeks. However, only nifedipine, enalapril, losartan, and propranolol reduced cardiac mass (>19%) within 4 weeks. Regression of cardiac hypertrophy was accompanied by a 50% to 300% increase in DNA fragmentation and a >20% reduction in DNA synthesis, resulting in a >20% reduction in cardiac DNA content after 4 weeks. Apoptosis induction occurred early and was transient within 4 weeks of nifedipine, enalapril, or losartan administration. With all regression-inducing drugs, the increase in DNA fragmentation occurred mainly in the subepicardium. Thus, transient induction of apoptosis in the subepicardium appears to be a characteristic feature of the early response to drug-induced regression of cardiac hypertrophy in spontaneously hypertensive rats.

Hepatocyte growth factor (HGF) is a unique growth factor that has many protective functions against renal damage. Our previous study demonstrated that HGF stimulated the growth of endothelial and epithelial cells without the replication of mesangial cells. Moreover, angiotensin (Ang) II significantly decreased local HGF production in mesangial cells. Therefore, we examined the effects of Ang II blockade on renal HGF expression and renal damage in experimental hypertensive rats. An angiotensin-converting enzyme inhibitor (cilazapril; 10 mg. kg(-1). d(-1)), an Ang II type 1 receptor antagonist (E-4177; 30 mg. kg(-1). d(-1)), hydralazine (8 mg. kg(-1). d(-1)), and vehicle were administered to 16-week-old stroke-prone spontaneously hypertensive rats (SHR-SP) for 3 weeks. Renal damage was evaluated with a computer analysis system, and renal HGF mRNA was measured by Northern blot analysis. Blood pressure of SHR-SP was significantly decreased by all drug treatments compared with vehicle. Moreover, cilazapril, E-4177, and hydralazine significantly decreased the thickening and necrosis of blood vessels compared with vehicle. Similarly, degeneration and necrosis of glomeruli were also markedly improved by cilazapril and E-4177 (P<0.01). We next examined the effects of Ang II blockade on renal HGF expression in SHR-SP. Renal HGF mRNA was markedly decreased in SHR-SP compared with Wistar-Kyoto rats, although Ang II blockade by cilazapril and E-4177 but not hydralazine significantly increased renal HGF mRNA in SHR-SP. Ang II blockade significantly increased renal HGF (a protective growth factor for tubular epithelial cells); thus, we examined tubular histological appearance. Degeneration and necrosis of tubules were significantly improved by cilazapril and E-4177 treatment (P<0.01). In addition, cell infiltration into the glomeruli and hemorrhage were also significantly reduced in SHR-SP treated with cilazapril or E-4177. The present data demonstrated the prevention of renal damage by Ang II blockade in SHR-SP, which was accompanied by a significant increase in renal HGF mRNA. Given the strong mitogenic activity and antiapoptotic actions of HGF on endothelial and epithelial cells, we believe that increased local HGF production by the blockade of Ang II may improve renal function in hypertension.

We investigated the pathophysiological significance of adrenomedullin (AM) in the development of left ventricular hypertrophy (LVH). LVH was produced by aortic banding (AB) in rats. The left ventricular weight/body weight (LV/BW) ratio, ventricular AM peptide and mRNA levels, and hemodynamics were measured at 1, 3, 7, and 21 days after the operation. Both LV/BW ratio and ventricular AM levels showed a significant increase from 1 day after the operation in the AB rats versus the sham-operated rats. Both increased in a time-dependent manner. The ventricular AM levels correlated with the LV/BW ratio (r=0.76, P<0.01). The AM mRNA levels were highly expressed at 1 day after the operation in the AB rats but showed no difference from 3 to 21 days after the operation between the AB and sham groups. The plasma AM levels showed a peak at 1 day after the operation in both groups. Then, we treated AB rats with an angiotensin-converting enzyme inhibitor (quinapril) in 2 doses (1 and 10 mg. kg-1. d-1) for 21 days. The quinapril treatment attenuated similarly both the LV/BW ratio and the ventricular AM levels. We also assessed the effects of AM and hydralazine administration for 7 days on the LV/BW ratio and hemodynamics of AB rats. Both AM and hydralazine administration reduced the blood pressure by approximately 10% compared with the nontreated AB rats, but a reduction of the LV/BW ratio was observed only in the AM-treated group (P<0.05). These results suggest that ventricular AM levels are elevated by chronic pressure overload in a time-dependent manner concomitant with the extent of LVH and that AM may play a pathophysiological role in the development of LVH in chronic pressure overload.

Radio-telemetry systems offer the ability to measure blood pressure and heart rate in experimental models of hypertension without the stress artifacts induced by some other methods. We therefore aimed to develop improved, nonparametric regression methods for radio-telemetry data and to use these to assess the effects of pharmacological interventions on cardiac and vascular hypertrophy in the stroke-prone spontaneously hypertensive rat. One control group and 5 groups treated either with losartan (alone or in combination with NG-nitro-L-arginine methyl ester [ L-NAME]), perindopril (also alone or in combination with L-NAME), or hydralazine plus hydrochlorothiazide were monitored for 4 weeks. Cardiac hypertrophy was assessed by the left ventricle plus septum weight to body weight ratio and vascular hypertrophy by flow-cytometry analysis of vascular smooth muscle cell polyploidy. Hemodynamic series were split into trend and cyclic components by the seasonal and trend decomposition procedure based on Loess and compared between groups by Loess regression modeling. Systolic and diastolic blood pressures were reduced systematically by losartan and perindopril (P<10(-10)) but to a lesser extent by hydralazine plus hydrochlorothiazide (P<10(-8)), and diurnal variation was reduced in the latter group (P<10(-6)). L-NAME significantly reduced the hypotensive effect only of losartan. Vascular and cardiac hypertrophy were significantly attenuated with losartan or perindopril, but were unchanged with other treatments. The new analysis proposed here identifies differential effects on trends and cyclic variation and associations with regression of end-organ damage for losartan and perindopril compared with hydralazine plus hydrochlorothiazide. The method offers a powerful tool for detailed investigation of radio-telemetry data.

A novel model of hypertension recently developed in our laboratory shows that neonatal degeneration of capsaicin-sensitive sensory nerves renders a rat responsive to a salt load with a significant rise in blood pressure. To determine the role of the renin-angiotensin system and the sympathetic nervous system in the development of hypertension in this model, newborn Wistar rats were given capsaicin 50 mg/kg SC on the first and second days of life. Control rats were treated with vehicle. After they were weaned, male rats were divided into 6 groups and subjected to the following treatments for 2 weeks: control+high sodium diet (4%) (CON-HS), capsaicin+normal sodium diet (0.5%) (CAP-NS), capsaicin+high sodium diet (CAP-HS), capsaicin+high sodium diet+losartan (10 mg/kg per day) (CAP-HS-LO), capsaicin+high sodium diet+prazosin (3 mg/kg per day) (CAP-HS-PR), and capsaicin+high sodium diet+hydralazine (10 mg/kg per day) (CAP-HS-HY). Levels of calcitonin gene-related peptide in dorsal root ganglia were decreased by capsaicin treatment (P<0.05). Both tail-cuff systolic blood pressure and mean arterial pressure were higher in CAP-HS and CAP-HS-PR than in CON-HS, CAP-NS, CAP-HS-LO, and CAP-HS-HY (P<0.05). The 24-hour urinary volume and sodium excretion were increased when a high sodium diet was given (P<0.05), but they were lower in CAP-HS, CAP-HS-LO, CAP-HS-PR, and CAP-HS-HY than in CON-HS (P<0.05). Urinary potassium excretion was not different among all 6 groups. We conclude that blockade of the angiotensin type 1 receptor with losartan but not antagonism of the alpha1-adrenoreceptor with prazosin prevents the development of salt-sensitive hypertension induced by sensory denervation. Sensory denervation impairs urinary sodium and water excretion in response to a high sodium intake, regardless of blood pressure, suggesting that sensory innervation plays a direct role in regulating the natriuretic response to sodium loading.

Septic shock involves systemic vasodilation mediated by proinflammatory cytokines. In essential hypertension, vascular and immune dysfunctions are closely associated. The response of hypertensive animals compared with normotensive controls to endotoxin (lipopolysaccharide; LPS) challenge is not known. Age-matched (12 weeks) normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) were exposed to intravenous injection of 10 mg/kg LPS. Survival rate at 24 hours was markedly higher in SHR than in WKY (12 of 15 and 3 of 15, respectively; P<0.01). Survival of LPS-injected SHR was not related to their hypertension because hydralazine-treated SHR with normalized pressure had similar survival rates, and WKY made hypertensive by clipping of one renal artery showed fatality similar to that of normotensive WKY. Continuous arterial pressure and sequential plasma levels of interleukin-6 (IL-6) and tumor necrosis factor (TNF) were measured in LPS-treated SHR and WKY. Both the duration of the delayed hypotensive phase and the systemic release of IL-6 were much lower in SHR than WKY, whereas both acute hypotension and plasma TNF peak were equivalent. We further explored in vitro the inflammatory response and showed that LPS-activated whole blood from SHR produced less TNF and IL-6 than WKY LPS-activated whole blood. Our results indicate that SHR have a greater ability to resist endotoxic shock than WKY. This is not related to their hypertension but is associated with an attenuated inflammatory response to LPS.

The purpose of this investigation was to evaluate the role of blood pressure in the proliferative response of vascular smooth muscle cells to systemic infusion of angiotensin II (Ang II). Our laboratory has previously shown that infusion of Ang II induces smooth muscle cell proliferation in rat mesenteric vessels and carotid arteries. Ang II, a strong vasopressor, raised systolic blood pressure in rats from 120 to 200 mm Hg at a dose of 435 ng x kg(-1) x min(-1) after 1 week of treatment. The question arises as to whether this development of hypertension is a primary contributor to the replicative activities observed in the arterial wall of the mesenteric arteries or the carotid arteries or whether Ang II alone, without an increase in blood pressure, is sufficient to stimulate proliferation in these vessels. In the previous studies, we found that Ang II stimulated smooth muscle cell replication in the carotid artery and in type III and type I mesenteric microvessels. This study demonstrates that although administration of hydralazine normalizes the animals' blood pressures, it does not suppress the mitogenic effect of Ang II. Thus, it appears that Ang II has a direct effect on cell proliferation.

Monocyte chemoattractant protein-1 (MCP-1), a potent monocyte chemoattractant synthesized by vascular cells and monocytes, has been proposed to be an important mediator of inflammatory responses in the arterial vasculature. It was recently demonstrated that hypertension is associated with an inflammatory response in the arterial wall. To determine the effect of hypertension on arterial MCP-1 expression, we induced hypertension in Sprague-Dawley rats by infusing angiotensin II (0.75 mg x kg[-1] x d[-1] SC) for 7 days. Using Northern blot analysis, we detected a 3.6-fold increase in MCP-1 mRNA in the aortas of hypertensive rats. When we normalized blood pressure in angiotensin II-treated rats through oral administration of the nonspecific vasodilator hydralazine (15 mg x kg[-1] x d[-1]), aortic MCP-1 mRNA expression was significantly reduced. Similar results were obtained with a norepinephrine model of hypertension. Taken together, these data suggest that mechanical factors may be responsible in part for the upregulation of expression. Consistent with this interpretation, we found that cultured rat aortic vascular smooth muscle cells exposed to mechanical strain (20% peak deformation at 1 Hz) exhibited a marked increase in MCP-1 expression, suggesting the hemodynamic strain imparted onto arterial cells in hypertension is an important stimulus underlying this phenomenon. These results provide important insights into the in vivo regulation of MCP-1 and have potential implications for understanding the influence of hypertension on atherosclerosis.

We evaluated the effect of different vasodilators on ventricular end-systolic stress by investigating the impact of sodium nitroprusside, nifedipine, and hydralazine on blood pressure, aortic stiffness, and wave reflection during drug-induced hypotension (to 80 mm Hg mean blood pressure) in normotensive (central aortic mean blood pressure, 116 to 119 mm Hg; systolic pressure, 133 to 137 mm Hg), nonanesthetized, unrestrained rats. Aortic stiffness was evaluated from the slope of the linear regression relating pulse wave velocity (PWV) to central aortic mean or pulse pressure. The fall in central aortic systolic blood pressure was less than the fall in mean pressure, especially after hydralazine (122+/-4 mm Hg; sodium nitroprusside, 107+/-2; and nifedipine, 112+/-3 mm Hg; P<.05). The PWV/mean pressure slope was linear, positive, and similar in all three groups (hydralazine, 3.3+/-0.2; sodium nitroprusside, 3.8+/-0.3; and nifedipine, 3.9+/-0.3 cm x s[-1]x mm Hg[-1]; P>.05). The PWV/pulse pressure slope was linear, negative, and less steep in the case of hydralazine (-4.9+/-0.6; sodium nitroprusside, -15.5+/-3.7; and nifedipine, -13.5+/-2.9 cm x s[-1] x mm Hg[-1]; P<.05). The travel time and augmentation index of the reflected wave were similar in all groups. In conclusion, sodium nitroprusside and nifedipine had a more beneficial effect on end-systolic stress than did hydralazine. This does not appear to be related to any specific effect on wave reflection or the "static" relationship between PWV and aortic mean blood pressure; it may be related to the effects of these drugs on the "dynamic" relationship between PWV and pulse pressure.

The present study evaluated the effects of lovastatin on renal function and the development of hypertension in spontaneously hypertensive rats (SHR). Four-week-old SHR were given lovastatin (10 mg/kg) or vehicle twice daily by gavage. After 4 weeks of treatment, mean arterial pressure was significantly lower in lovastatin-treated SHR (131 +/- 4 mm Hg, n=5) than in control animals (160 +/- 4 mm Hg, n=12) (P<.05). The fall in arterial pressure in lovastatin-treated rats was accompanied by changes in renal function. The slope of the relationship between arterial pressure and sodium excretion was threefold greater in lovastatin-treated SHR (n=6) than in control rats (n=6), and this was associated with significant elevations in renal medullary blood flow and renal interstitial hydrostatic pressure. Glomerular filtration rate was 17% higher in lovastatin-treated SHR (n=6) than in control rats (n=6) (0.94 +/- 0.05 versus 0.81 +/- 0.07 mL/min per g of kidney weight, P<.05). The wall-to-lumen area ratio of renal arterioles was significantly reduced in lovastatin-treated SHR compared with vehicle-treated rats (0.86 +/- 0.05 versus 1.08 +/- 0.04 for vessels with inner diameters <50 microm and 0.62 +/- 0.02 versus 0.75 +/- 0.04 for vessels with inner diameters of 50 to 100 microm, P<.05). These results indicate that chronic treatment with lovastatin shifts the relations between renal medullary blood flow, renal interstitial pressure, sodium excretion, and renal perfusion pressure to lower levels of arterial pressure and attenuates the development of hypertension and renal vascular hypertrophy in SHR.

Our previous studies have shown that ethanol selectively counteracts centrally mediated hypotensive responses. This study investigated the role of cardiac output and peripheral resistance in the antagonistic interaction between ethanol and antihypertensive drugs. Changes in blood pressure, heart rate, cardiac index, stroke volume, and peripheral resistance elicited by clonidine and subsequent ethanol or saline administration were evaluated in conscious rats. The aortic barodenervated rat was employed because it exhibits greater hypotensive responses to clonidine compared with the intact rat. Aortic barodenervation elicited acute rises in blood pressure, heart rate, and peripheral resistance, whereas cardiac index and stroke volume were not altered. The blood pressure of conscious aortic barodenervated rats returned to sham-operated levels by 48 hours due to concomitant reductions in cardiac index and stroke volume; the peripheral resistance, however, remained significantly elevated. Clonidine (30 microg/kg, I.V.) elicited greater decreases in blood pressure in aortic barodenervated compared with sham-operated rats. The hypotension was caused by decreases in cardiac index and stroke volume because peripheral resistance did not change. Ethanol (1 g/kg, I.V.) counteracted the hypotensive effect of clonidine and raised blood pressure to levels higher than preclonidine values. Significant (P<.05) increases in cardiac index and stroke volume and decreases in peripheral resistance accompanied the pressor effect of ethanol. Additional control groups were included in the study to determine the selectivity of the interaction. A dose of hydralazine (0.5 mg/kg, I.V.) was used that produced similar hypotension to that evoked by clonidine in aortic barodenervated rats. Hydralazine-evoked hypotension was similar in denervated and control rats and resulted from significant reductions in peripheral resistance. Reflex increases in heart rate and stroke volume and hence cardiac output were observed. Ethanol given after hydralazine produced a short-lived pressor effect (<5 minutes versus 40 minutes in the case of clonidine) and counteracted the sympathetically mediated increases in cardiac output, stroke volume, and heart rate. These findings support our hypothesis that ethanol selectively counteracts hypotensive responses of central origin by reversing the reduction in cardiac output elicited by clonidine.

To assess whether acute nitric oxide (NO) blockade could unmask the vascular actions of endogenous endothelin, we tested the effects of the endothelin type A/type B (ET(A)/ET(B)) receptor antagonist bosentan and the selective ET(A) antagonist FR 139317 on blood pressure, plasma volume, and albumin escape after inhibition of NO synthesis with N(G)-nitro-L-arginine methyl ester (L-NAME). Conscious, chronically catheterized rats received L-NAME in the absence and presence of 17.4 micromol/kg (10 mg/kg) bosentan or 3.8 micromol/kg (2.5 mg/kg I.V., 10 minutes before L-NAME) FR 139317. Red blood cell volume and plasma volume were determined with chromium-51-tagged erythrocytes and iodine-125-labeled albumin, respectively. L-NAME (0.46 to 7.42 micromol/kg [0.125 to 2 mg/kg]) induced a dose-dependent increase in blood pressure, which was attenuated by 60% and 48% with bosentan and FR 139317, respectively (P<.01). L-NAME (7.42 micromol/kg) also increased hematocrit. This effect was associated with an increase in total-body albumin escape, which is reflected by a 14% reduction in plasma volume. Red blood cell volume remained unchanged. L-NAME promoted albumin escape primarily in the lung, heart, liver, kidney, and gastrointestinal tract. Both bosentan and FR 139317 markedly reduced these effects of L-NAME. Furthermore, L-NAME increased plasma levels of immunoreactive endothelin-1 from 8.6+/-0.4 (n=10) to 14.7+/-1.4 pg/mL (n=9, P<.01). These results demonstrate that the pressor response, losses in plasma volume, and increase in albumin escape observed after inhibition of NO synthesis are in part the consequence of unmasking the actions of endogenous endothelin, which are mediated predominantly via ET(A) receptors. These findings suggest a role for endogenous endothelin in the regulation of vascular functions in conditions when NO formation by endothelial cells is impaired.

Intrathecal administration of nicotinic agonists previously has been shown to result in exaggerated pressor and heart rate responses as well as greater nociceptive behavior in adult (12-week-old) spontaneously hypertensive rats (SHR) than in age-matched normotensive Wistar-Kyoto rats (WKY). Paradoxical to these augmented responses to nicotinic agonists in SHR, nicotinic receptor number in the spinal cord as measured by cytisine binding sites is lower in adult SHR than normotensive WKY and Sprague-Dawley rats. Using the high-affinity agonist epibatidine, we found similar differences in receptor number between strains in both in vitro ligand binding experiments with spinal cord membranes and in situ autoradiographic analyses. Spinal nicotinic receptor number did not differ in 5-week-old prehypertensive SHR and age-matched WKY; however, receptor numbers were higher in young rats of both strains than in their adult counterparts. Antihypertensive treatment (25 mg/kg per day hydralazine PO) in 6-week-old SHR from 6 to 12 weeks of age markedly reduced the progressive rise in blood pressure yet did not alter nicotinic receptor number compared with untreated rats. Similar treatment of WKY with hydralazine produced a slight fall in blood pressure but no change in receptor number. Thus, normalization of blood pressure by hydralazine in SHR does not result in a return of receptor expression to levels seen in normotensive rats. Higher centrally mediated pressor activity or augmented postcoupling events after neuronal nicotinic receptor stimulation may slowly downregulate expression of spinal nicotinic receptors in this genetically hypertensive rat strain.

We studied the effect of chronic (7 days) angiotensin II (Ang II) infusion in nonpressor and pressor doses on cardiovascular mass and expression of alpha- and beta-myosin heavy chain genes in the left ventricle in normotensive Wistar rats. An increased left ventricular mass was observed in rats receiving non-pressor and pressor doses of Ang II, but only high doses increased arterial pressure. Normalization of arterial pressure during Ang II infusion by losartan, a specific Ang II receptor antagonist, or hydralazine had different effects on left ventricular mass. Losartan prevented the increased left ventricular mass, and hydralazine did not affect left ventricular mass. Northern blot analysis showed that the switch in left ventricular myosin isoform mRNA from the adult to the fetal pattern occurred only in rats given the pressor Ang II dose. Both losartan and hydralazine, in parallel with the normalization of arterial pressure, prevented this myosin isoform switch. Thus, these data suggest that the Ang II-induced increase in left ventricular mass was not dependent on pressure overload, but the switch in myosin isoform mRNA from the adult to the fetal pattern was dependent on pressure overload.