Search

To provide novel insights into the pathogenesis of heart failure-induced renal dysfunction, we compared the effects of ACE inhibitor (ACEi) and AT1 receptor blocker (ARB) on systemic and kidney hemodynamics during heart failure in normotensive HanSD and hypertensive transgenic (TGR) rats. High-output heart failure was induced by creating an aorto-caval fistula (ACF). After five weeks, rats were either left untreated or treatment with ACEi or ARB was started for 15 weeks. Subsequently, echocardiographic, renal hemodynamic and biochemical measurements were assessed. Untreated ACF rats with ACF displayed significantly reduced renal blood flow (RBF) (HanSD: 8.9 ± 1.0 vs. 4.7 ± 1.6; TGR: 10.2 ± 1.9 vs. 5.9 ± 1.2 ml/min, both P P P P

Introduction: There is a need to implement a preclinical model in addition to the well established ischemic or volume-overload models that would mimic the clinical course of patients with chemotherapy-induced heart failure. Doxorubicin is an anthracycline chemotherapeutic that is widely used in oncology, although its cardiotoxicity. Hypothesis: Doxorubicin-induced left ventricular dysfunction in rats fulfills echocardiography and hemodynamic characteristics of chemotherapy-induced heart failure. Methods: We randomly assigned Ren-2 transgenic hypertensive (TGR, n = 17) and normotensive rats (HanSD, n = 22), at the age of 8 weeks to doxorubicin (2.5 mg/kg in 0.5 ml of normal saline) or placebo in 6 intraperitoneal doses within two weeks (cumulative doxorubicin dose 15 mg/kg). Two weeks later, we performed echocardiography study, pressure-volume analysis (PV), and we weighed the organs. Results: In doxorubicin groups, there was a decrease in the left ventricle weight (1,22 vs. 0,85 g in TGR), while an increase in wall stress (22036 vs. 29754 μL*mmHg/g in TGR). Echocardiography suggested heart remodeling with a decrease in relative wall thickness - RWT (1.02 vs. 0.65 mm in TGR), and together with PV analysis showed a decrease in systolic parameters - left ventricle ejection fraction - LVEF (71.41 vs. 59.96 % in TGR), end-systolic pressure-volume ratio - ESPVR (0.82 vs. 0.45 mmHg/uL in TGR) and preload recruitable stroke work - PRSW (75.71 vs. 60.98 mmHg in TGR). Ventricular-arterial coupling (VAC = Ea/Ees, a measure of cardiac efficiency) was worsened in the doxorubicin groups (1.69 vs. 2.52 in TGR). For all the above p < 0.05, in HanSD, the results were similar (all p < 0.05). Conclusions: Our results suggest that systolic dysfunction and decrease of cardiac efficiency in this model could be caused by heart atrophy, and such an animal model could potentially be an easily reproducible model of chemotherapy-induced heart failure in preclinical cardio-oncology studies.

To provide novel insights into the pathogenesis of heart failure-induced renal dysfunction, we compared the effects of ACE inhibitor (ACEi) and AT1 receptor blocker (ARB) on systemic and kidney hemodynamics during heart failure in normotensive HanSD and hypertensive transgenic (TGR) rats. High-output heart failure was induced by creating an aorto-caval fistula (ACF). After five weeks, rats were either left untreated or treatment with ACEi or ARB was started for 15 weeks. Subsequently, echocardiographic, renal hemodynamic and biochemical measurements were assessed. Untreated ACF rats with ACF displayed significantly reduced renal blood flow (RBF) (HanSD: 8.9 ± 1.0 vs. 4.7 ± 1.6; TGR: 10.2 ± 1.9 vs. 5.9 ± 1.2 ml/min, both P

Rationale and Objective: We recently showed that increasing epoxyeicosatrienoic acids (EETs) in kidney by blocking soluble epoxide hydrolase (sEH), an enzyme responsible for EETs degradation, markedly attenuated the development of renal dysfunction and progression of aorto-caval (ACF)-induced congestive heart failure (CHF) in Ren-2 transgenic hypertensive rats (TGR). Therefore, in this study we examined if additional inhibition of sEH to RAS blockade could further improve the course of ACF-induced CHF in TGR. Methods: The treatment regimens were started from one week after creation of ACF and the follow-up period was 60 weeks. RAS blockade was achieved by administration of angiotensin-converting enzyme inhibitor (ACEi, trandolapril, 3 mg/L in drinking water) and sEH was blocked using a sEH inhibitor (sEHi, c -AUCB, 3 mg/L in drinking water). The following experimental groups were investigated: 1) Sham-operated TGR; 2) Untreated ACF TGR; 3) ACF TGR + ACEi; 4) ACF TGR + ACEi + sEHi (n = 36 in each ACF group). In separate groups renal hemodynamics and excretory function were evaluated two weeks post-ACF, just before the onset the decompensated phase of CHF. Results: After 29 weeks post-ACF, no animal survived. ACEi treatment greatly improved the survival rate (87%) at the end of study. Surprisingly, combined treatment with ACEi and sEHi worsened the rate (53%, p < 0.05). After 2 weeks post-ACF, untreated TGR group showed lower mean arterial pressure (MAP) (124 ± 3 vs. 146 ± 4 mmHg, p < 0.05), renal blood flow (7.6 ± 0.3 vs. 10.5 ± 0.3 mL.min -1 .g -1 , p < 0.05) and absolute sodium excretion (0.18 ± 0.06 vs. 1.09 ± 0.19 μmol.min -1 .g -1 , p Conclusion: We found that addition of sEHi to ACEi treatment did not provide better protection against CHF progression and the survival rate, indeed, decreased significantly. Thus, increasing bioavailability of tissue EETs in individuals with pharmacologically-induced suppression of the RAS is not a promising approach to further attenuate renal dysfunction and progression of CHF.

Rationale and Objective: We showed recently that increasing kidney tissue epoxyeicosatrienoic acids (EETs) by blocking soluble epoxide hydrolase (sEH) and thereby blocking EETs degradation to inactive dihydroxyeicosatrienoic acids (DHETEs) substantially attenuated the progression of chronic kidney disease (CKD) in Ren-2 transgenic hypertensive rats (TGR) subjected to 5/6 renal mass reduction (5/6 NX). In this study we examined if in this model addition of sEH inhibition to the complex (dual) renin-angiotensin system (RAS) blockade would bring additional renoprotective effects in already established CKD. Methods: TGR aged 9 weeks underwent 5/6 NX and then were left untreated for 6 weeks to develop CKD. Then dual RAS blockade : ACE inhibition (trandolapril) + angiotensin AT 1 receptor blockade (losartan) was instituted, alone or combined with sEH inhibition (c-AUCB, 3 mg/l in drinking water). During the 60 weeks’ follow-up period albuminuria and urinary creatinine excretion was repeatedly determined. The following experimental groups were investigated: ; 1) sham-operated TGR; 2) Untreated 5/6 NX TGR; 3) 5/6 NX TGR + RAS blockade ; 4) 5/6 NX TGR + RAS + sEH blockade. Sham-operated transgene-negative normotensive Hannover-Sprague Dawley (HanSD) rats served as basic controls. In separate groups renal glomerular and tubulointerstitial injury was assessed, and effects of two weeks’ treatments on systolic blood pressure (SBP, measured by telemetry) and on kidney ANG II, ANG 1-7, EETs and DHETEs levels were determined. Results: All untreated TGR died by week 14 after 5/6 NX. RAS blockade increased the final survival rate to 23%, normalized SBP (116 ± 3 vs. 198 ± 3 mmHg, p Conclusion: Addition of sEH blockade to the RAS blockade brings additional renoprotective effects on the CKD progression in 5/6 NX TGR, even when applied in the advanced phase of the disease.

Results of our previous studies have suggested that enhanced generation of superoxide (O 2 − ) may contribute to the pathophysiology of hypertension in Ren-2 transgenic rats (TGR). The present study was performed to evaluate in TGR the effects of chronic treatment with the O 2 − scavenger tempol and the antioxidant apocynin on the development of hypertension. Systolic blood pressure (SBP) was monitored from 30 to 99 days of age in TGR and in normotensive Hannover Sprague–Dawley (HanSD) rats. At the end of the experiment, urinary protein and 8-isoprostane excretion were determined and angiotensin II (ANG II) and malondialdehyde (MDA) levels were measured in kidney and cardiac tissues. Cardiac hypertrophy was assessed as the ratio of left heart ventricle weight to tibia length (LVW/TL). Although tempol and apocynin treatment in TGR significantly decreased 8-isoprostane excretion and MAD tissue concentrations as compared with untreated TGR, it did not alter the course of SBP, LVW/TL ratio, proteinuria or ANG II levels that were enhanced as compared with HanSD rats. Our data suggest that the development of hypertension in TGR is clearly ANG II-dependent but the contribution of oxidative stress to the development of hypertension in this model appears to be negligible.

Objective The present study was performed to characterize the autoregulatory efficiency of renal blood flow and glomerular filtration rate and the pressure-natriuresis relationship in transgenic rats with inducible angiotensin II (ANG II)-dependent hypertension (Cyp1a1-Ren-2 rats). Methods The renin gene was induced in Cyp1a1-Ren-2 rats through dietary administration of the natural xenobiotic indole-3-carbinol (I3C, 0.3%) for 12 and 24 h, respectively. Noninduced rats served as controls. Anesthetized rats were prepared for renal function studies and an aortic clamp was placed above the junction of the left renal artery to regulate the level of renal arterial pressure. Plasma renin activity, ANG II and aldosterone levels were measured at the end of the experiment by radioimmunoassay. Results Administration of I3C resulted in progressive increases in plasma renin activity and plasma and kidney ANG II levels; however, it did not significantly alter aldosterone levels as compared with those in noninduced rats. I3C induction for 12 h did not cause significant changes in blood pressure as compared with those in noninduced rats. I3C induction for 24 h elicited a significant rise in blood pressure. Twelve-hour I3C induction caused an impairment of the autoregulatory efficiency of renal blood flow and glomerular filtration rate and of the pressure-natriuresis relationship as compared with that in noninduced rats. In addition, 24 h I3C induction of the renin gene resulted in a marked reduction in renal blood flow and glomerular filtration rate and a further impairment of the pressure-natriuresis mechanism as compared with that in noninduced rats. Conclusion Our findings indicate that an impairment of the pressure-natriuresis mechanism precedes the development of ANG II-dependent hypertension in Cyp1a1-Ren-2 transgenic rats.

The present study was performed to examine in two-kidney, one-clip (2K1C) Goldblatt hypertensive mice: first, the relative contribution of angiotensin II receptor subtypes 1A (AT(1A)) and 1B (AT(1B)); second, the role of angiotensin II type 2 (AT(2)) receptors in the development of hypertension in wild-type (AT(1A)+/+) and AT(1A) receptor knockout (AT(1A)-/-) mice; and third, the role of increased nitric oxide synthase activity in counteracting the hypertensinogenic action of angiotensin II in this model.AT(1A)+/+ and AT(1A)-/- mice underwent clipping of one renal artery and were infused with either saline vehicle or selective AT(2) receptor agonist CGP-42112A (CGP). Blood pressure was monitored by radiotelemetry. Blood pressure responses to the nitric oxide synthase inhibitor nitro-L-arginine-methyl-ester were evaluated.AT(1A)+/+ mice responded to clipping by a rise in blood pressure that was not modified by CGP infusion. Clip placement caused a slight increase in blood pressure in AT(1A)-/- mice that remained significantly lower than in AT(1A)+/+ mice. Acute nitric oxide synthase inhibition caused greater increase in blood pressure in 2K1C/AT(1A)+/+ than in AT(1A)+/+ mice.The present data support the critical role of AT(1A) receptors in the development of 2K1C hypertension, whereas AT(1B) receptors play only a minor role in blood pressure regulation in this model of angiotensin II-dependent hypertension. Activation of AT(2) receptors does not play an antagonistic role in the AT(1) receptor-mediated hypertensinogenic actions of angiotensin II in this model. Finally, enhanced nitric oxide synthase activity plays a protective role by counteracting the vasoconstrictor influences of angiotensin II in 2K1C hypertensive mice.

The aim of this study was first to evaluate the effects of persistent or transient blockade of the angiotensin II (ANG II) receptor AT1 on the development of hypertension and end-organ damage in hypertensive Ren-2 transgenic rats (TGR), and second to assess the potential role of AT2 receptors in the control of blood pressure (BP) in this monogenetic model of hypertension. Male heterozygous TGR and Hannover Sprague-Dawley (HanSD) rats fed a normal salt diet were treated from day 32 of age either persistently until the end of the experiment (day 100 of age) or transiently until day 56 of age with the selective AT1 receptor antagonist candesartan or with the combination of candesartan and the AT2 receptor antagonist PD 123319. Persistent treatment with candesartan completely prevented the rise in BP, proteinuria and the increase in left ventricular weight/body weight ratio, whereas transient treatment with candesartan was effective only as long as the drug was administered. In the presence of candesartan, PD 123319 was without effect. Our results show that in male heterozygous TGR persistent candesartan treatment completely prevented hypertension and end-organ damage as long as the drug was administered, whereas transient AT1 receptor blockade had no long-term effects.

The effects of the human renin inhibitor aliskiren on blood pressure (BP), end-organ damage, proteinuria, and tissue and plasma angiotensin (ANG) II levels in young and adult heterozygous Ren-2 transgenic rats (TGR) were evaluated and compared with the effect of the ANG type 1 (AT1) receptor blocker losartan during treatment and after 12 days after the withdrawal of drug treatments. BP was monitored by telemetry from the age of 32 days on (young rats) and at 100 days (adult rats). Aliskiren (10 mg·kg−1·day−1in osmotic minipumps) or losartan (5 mg·kg−1·day−1in drinking water) treatment was applied for 28 days in young rats and for 70 days in adult rats. In young untreated TGR, severe hypertension rapidly evolved. Adult untreated TGR exhibited stable established hypertension. Both aliskiren and losartan fully prevented the development of hypertension and cardiac hypertrophy in young TGR and normalized BP and cardiac hypertrophy in adult TGR. After cessation of aliskiren treatment in both young and adult TGR BP and cardiac hypertrophy were persistently reduced, while after losartan withdrawal BP and cardiac hypertrophy rapidly increased. In adult aliskiren-treated rats proteinuria was significantly reduced compared with losartan (the effect persisting after withdrawal of treatment), and this decrease strongly correlated with normalization of glomerular size in these animals. In conclusion, aliskiren and losartan had similar antihypertensive effects during chronic treatment, but the antihypertensive and organoprotective effects of aliskiren were persistent even after the 12-day washout period. The durable effect on proteinuria can possibly be attributed to the normalization of glomerular morphology.

Objective We evaluated the effects of salt restriction and of increasing dietary salt loading on blood pressure and the renin-angiotensin system in transgenic rats with inducible hypertension. Methods Hypertension was induced in Cyp1a1-Ren-2 rats through dietary administration of the natural xenobiotic indole-3-carbinol (0.3%), which activates the renin gene. Rats were fed either a normal-salt diet (0.6% NaCl), three different high-salt diets (2, 4 and 8% NaCl) or a low-salt diet (

Objective In the present study we compared the effects of treatment with the AT 1 receptor antagonist candesartan and of 'triple therapy' (hydralazine, hydrochlorothiazide, reserpine) on the course of blood pressure, cardiac hypertrophy and angiotensin II concentrations after induction of hypertension in transgenic rats with inducible expression of the mouse renin gene (Cyp1a1-Ren-2 rats). Methods Hypertension was induced in Cyp1a1-Ren-2 rats through dietary administration of the natural xenobiotic indole-3-carbinol (I3C, 0.3%) for 4 days. Starting on the day before administration of I3C, rats were treated either with candesartan or received triple therapy for 9 days. Systolic blood pressure was measured in conscious animals. Rats were decapitated and angiotensin II levels in plasma and in whole kidney and left ventricular tissues were determined by radioimmunoassay. Results Administration of I3C resulted in the development of severe hypertension and cardiac hypertrophy that was accompanied by marked elevations of plasma and tissue angiotensin II concentrations. Candesartan treatment prevented the development of hypertension and cardiac hypertrophy and was associated with a reduction of tissue angiotensin II concentrations. In contrast, triple therapy, despite maintaining systolic blood pressure in the normotensive range, did not prevent the development of cardiac hypertrophy and tissue angiotensin II augmentations. Conclusions Our findings indicate that hypertension in Cyp1a1-Ren-2 rats is a clearly angiotensin II-dependent model of hypertension with elevated circulating and tissue angiotensin II concentrations, and that antihypertensive treatment with AT 1 receptor blockade is superior to conventional triple therapy in effective protection against hypertension-induced end-organ damage in this rat model.

Objective Since there is as yet no general agreement regarding the role of plasma and kidney angiotensin II (ANG II) in the development of hypertension in Ren-2 transgenic rats (TGR), in the present study we evaluated plasma and kidney ANG II levels in anesthetized and conscious TGR and in normotensive Hannover-Sprague-Dawley rats (HanSD) fed a normal salt diet (NS). Given the importance of ANG II in the development of salt-sensitive hypertension, and the fact that hypertensinogenic actions of ANG II are mediated via ANG II type 1 (AT1) receptors, the effects of high salt (HS) intake and of sodium depletion on blood pressure (BP), ANG II levels and kidney AT1 receptor protein expression in TGR and HanSD were also examined. Methods Rats were maintained on a NS diet (0.6% NaCl) or fed a HS diet (2% NaCl) for 4 days or were sodium depleted (40 mg/l furosemide for 1 day followed by 3 days of 0.01% NaCl diet). They were sacrificed either by an overdose of anesthetic (thiopental sodium) or by decapitation (without anesthetic) and plasma and kidney ANG II levels were determined by radioimmunoassay during the prehypertensive (32 days old), the early (52 days) and the maintenance (90 days) phases of hypertension. Total kidney AT1 receptor protein levels were assessed by Western blot analysis. Results In anesthetized animals fed the NS diet, plasma ANG II levels were lower in 32-day-old TGR than in HanSD, but at 52 and 90 days of age no significant differences were noted. ANG II concentrations in kidney tissue were similar in 32- and 90-day-old TGR and HanSD, but were higher in 52-day-old TGR than in HanSD. In contrast, in conscious animals immediately after decapitation, plasma and kidney ANG II levels were higher in TGR than in HanSD at all ages. HS diet did not change BP but suppressed ANG II levels in HanSD at all ages. In contrast, HS diet increased BP but did not decrease plasma and kidney ANG II levels in TGR at all ages. Sodium restriction did not alter BP and resulted in a marked increase in ANG II levels in HanSD, but caused a significant decrease in BP in TGR without altering plasma or tissue ANG II concentrations. There were no significant differences in renal AT1 receptor protein expression between HanSD and TGR at any age of any of the experimental groups. Conclusions On the basis of our present results we conclude that TGR exhibit a disrupted interaction between sodium homeostasis and the regulation of the renin-angiotensin system (RAS) activity which results in the loss of BP regulation in this model.

Background: Previous studies have implicated that normotensive rats with normal renal renin activity respond to anesthesia and surgery with greater increases in plasma and kidney angiotensin II (ANG II) concentrations than ANG II-dependent hypertensive rats with intrarenal renin depletion. In the present study, we therefore compared plasma and kidney ANG II levels in anesthetized and conscious normotensive and ANG II-dependent hypertensive rats. Methods: Salt-replete Hannover-Sprague-Dawley rats (HanSD) served as controls. As models of ANG II-dependent hypertension we used: 1st, transgenic rats harboring the Ren-2 renin gene (TGR); 2nd, two-kidney, one-clip (2K1C) Goldblatt hypertensive rats, and, 3rd, ANG II-infused hypertensive rats. As additional model with enhanced renin-angiotensin system (RAS) activity, salt-depleted HanSD and TGR were employed. Results: In anesthetized salt-repleted HanSD, plasma and kidney ANG II levels were higher than in salt-repleted TGR, ANG II-infused and 2K1C rats. Salt depletion caused marked increases in ANG II levels in HanSD but did not alter them in TGR. In contrast, in conscious animals immediately after decapitation plasma and kidney ANG II levels were similar in salt-repleted and salt-depleted TGR, in ANG II-infused rats, in the clipped kidney of 2K1C rats and in salt-depleted HanSD and in all these groups they were significantly higher than in salt-repleted HanSD. Conclusions: These findings indicate that anesthesia increases plasma and kidney ANG II levels in HanSD to a greater degree than in ANG II-dependent models of hypertension. Therefore, the results from studies employing anesthetized animals must be interpreted with caution.

Objective We investigated the responses of mean arterial pressure and renal blood flow to intravenous and intrarenal angiotensin II, plasma and kidney angiotensin II concentrations and renal angiotensin receptor subtype 1 protein expression, and renal functional responses to intravenous and intrarenal angiotensin receptor 1 blockade with candesartan. Methods In male anaesthetized transgenic rats and Hannover Sprague-Dawley rats aged 36-38 days mean arterial pressure and renal blood flow were determined after intravenous and intrarenal boluses of angiotensin II. Mean arterial pressure, renal blood flow and sodium excretion after intravenous or intrarenal candesartan were studied. Plasma and kidney angiotensin II concentrations were determined by radioimmunoassay. Renal angiotensin receptor subtype 1 protein levels were analysed by immunoblotting. Results The responses of mean arterial pressure and renal blood flow to angiotensin II were significantly greater in transgenic than in Hannover Sprague-Dawley rats. The administration of candesartan resulted in comparable decreases in mean arterial pressure and increases in renal blood flow and sodium excretion in both groups of rats. Renal angiotensin receptor subtype 1 protein levels were no different between Hannover Sprague-Dawley and transgenic rats. Conclusions Plasma and kidney angiotensin II levels were lower in anaesthetized transgenic rats but, in contrast, were higher in decapitated transgenic rats when compared with Hannover Sprague-Dawley rats, suggesting that the kidney function of prehypertensive transgenic rats is under inappropriately high angiotensin II-dependent influence.

OBJECTIVE: The first aim of the present study was to assess plasma and kidney angiotensin II (ANG II) levels and renal cortical ANG II receptor subtype 1A (AT1A) mRNA expression in hypertensive Ren-2 transgenic rats (TGR) and in normotensive Hannover Sprague-Dawley (HanSD) rats. The second aim was to investigate potential differences between TGR and HanSD in blood pressure (BP) and renal functional responses to either intravenous (i.v.), i.e. systemic, or intrarenal (i.r.) AT1 receptor blockade with candesartan. METHODS: Rats were anesthetized and prepared for clearance experiments. In series 1, ANG II concentrations were assayed by radioimmunoassay and renal cortical AT1A mRNA expression by semiquantitative reverse transcriptase-polyacrylamide gel electrophoresis. In series 2, BP and renal functional responses were evaluated after either i.v. or i.r. bolus administration of candesartan. RESULTS: Plasma and kidney ANG II levels were significantly lower in TGR than in HanSD (39 +/- 5 versus 107 +/- 19 fmol/ml and 251 +/- 41 versus 571 +/- 95 fmol/g, respectively, P < 0.05). Renal AT1A mRNA expression was not different between TGR and HanSD. Intravenous candesartan caused comparable decreases in BP in TGR and HanSD and did not change renal plasma flow (RPF) or absolute and fractional sodium excretion in HanSD. In contrast, i.v. candesartan significantly increased RPF (+27 +/- 6%, P < 0.05) and absolute and fractional sodium excretion (+49 +/- 10 and + 42 +/- 9%, respectively P < 0.05) in TGR without changing glomerular filtration rate (GFR). Acute i.r. candesartan increased RPF by +36 +/- 6% (P < 0.05) in TGR but not in HanSD with a greater rise in absolute and fractional sodium excretion in TGR (+124 +/-8 and 97 +/- 9%, respectively) than in HanSD (+81 +/- 9 and +69 +/- 8%, respectively) (P < 0.05). CONCLUSIONS: The enhanced responses of RPF and sodium excretion to AT1 receptor blockade in TGR suggest that renal hemodynamics and sodium excretion in TGR are under strong ANG II influence. The compromised ability of the kidney to respond to BP elevations by appropriate increases in sodium excretion may contribute to the maintenance of high BP in TGR. Thus, the present findings provide new insights into the pathophysiology of hypertension in this model.