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This study was designed to investigate the cardiovascular consequences of oral administration of Cedrelopsis grevei (CG) in normotensive rats. Experiments were designed to investigate fiemodynamic parameters in vivo as well as the consequences of CG treatment on the vasoconstriction response to norepinephrine and the vasorelaxant response to ACh ex vivo in isolated aortas and small mesenteric arteries (SMA). Treatment of male Wistar rats with 80 mg/kg CG for 4 wk induced a progressive decrease in systolic blood pressure. In the aorta, CG did not significantly alter the response to norepinephrine despite the participation of extraendothelial nitric oxide (NO)-induced hyporeactivity. In the SMA, contraction to norepinephrine was not modified by CG treatment even though it enhanced the participation of endothelial NO. Endothelium-dependent relaxation to ACh was increased in both the aorta and SMA from CG-treated rats. In the aorta from CG-treated rats, the mechanism involved superoxide dismutase (SOD)- and catalase-sensitive free radical production. The latter was associated with enhanced expression of Cu/Zn SOD and endothelial NO synthase. These results suggest that oral administration of CG produces a decrease in blood pressure in normotensive rats. This hemodynamic effect was associated with enhanced endothelium-dependent relaxation and an induction of Cu/Zn SOD and endothelial NO synthase expressions in the vessel wall. They also show subtle mechanisms that compensate for the increased participation of NO to maintain unchanged agonist-induced contractility. These data provide a pharmacological basis for the empirical use of CG against cardiovascular diseases. blood pressure; vasoconstriction

An analysis of phenotypic modulation of rat aortic smooth muscle cells (SMC), to examine the expression and role of angiotensin II receptor, confirms that the proliferative and the contractile SMC phenotype exhibit expression of AT1 receptors coupled to phospholipase C through a protein. Proliferative phenotype involves obstructed coupling to Ca2+ release. Phenotype modulation of SMC failed to exhibit AT2 receptor expression.

Experiments on rat femoral arteries reveal that Escherichia coli lipopoly saccharide (LPS) triggers the formation of a L-arginine-derived relaxing factor by a predominantly extra-endothelial process. The continuous nitric oxide synthase-mediated nitric oxide production probably reduces the relaxing effect in LPS-exposed arteries. The mechanism may be involved in mortality- causing factors that are observed during sepsis and morphological injury.

Abstract: Objective: Chronic administration of moderate amounts of red wine has been associated with a protective effect on the cardiovascular system. This study examined whether red wine polyphenols prevent the angiotensin II (Ang II)-induced hypertension and endothelial dysfunction in rats, and, if so, to elucidate the underlying mechanism. Methods: Hypertensive rats were obtained by a 14-day infusion of Ang II. Red wine polyphenols were administered in the drinking water one week before and during the Ang II infusion. Arterial pressure was measured in conscious rats. Ex vivo vascular relaxation was assessed in organ chambers, vascular superoxide anion production by dihydroethidine and vascular NADPH oxidase expression by immunohistochemistry. Results: Ang II-induced hypertension was associated with decreased relaxation to acetylcholine but not to red wine polyphenols. The Ang II treatment also increased vascular superoxide anion production and expression of nox1 and p22phox NADPH oxidase subunits. Intake of red wine polyphenols prevented the Ang II-induced hypertension and endothelial dysfunction and normalized vascular superoxide anion production and NADPH oxidase subunit expression. Red wine polyphenol treatment alone did not affect blood pressure. Conclusion: Intake of red wine polyphenols prevents Ang II-induced hypertension and endothelial dysfunction. Prevention of vascular NADPH oxidase induction and preservation of arterial nitric oxide availability during Ang II administration likely contribute to this effect. [Copyright &y& Elsevier]

1 The present study was aimed to characterize the effects of ageing on vascular contraction by noradrenaline in rat isolated arteries. The existence of vascular bed heterogeneity was investigated in endothelium-denuded conductance (aorta) and resistance (small mesenteric artery, SMA) arteries, with respect to Ca[sup 2+] handling, Ca[sup 2+] sensitization or Ca[sup 2+]-independent mechanisms. 2 In both arteries, contractions to noradrenaline were not different between adult and aged rats. 3 In Ca[sup 2+]-free medium, noradrenaline elicited a transient increase in tension that was reduced by the Ca[sup 2+] mobilizing agents, ryanodine and thapsigargin, in arteries from adult rats. A loss of the thapsigargin- but not the ryanodine-sensitive component of noradrenaline-induced contraction was observed in the two arteries from aged rats. 4 After depletion of Ca[sup 2+] stores with noradrenaline, addition of exogenous CaCl[sub 2] produced a sustained contraction that was decreased to the same extent by the protein kinase C inhibitor, GF 109203X and the tyrosine kinase inhibitor, tyrphostin A-23, in arteries from adult and aged rats. The Rho-associated protein kinase inhibitor, Y-27632, caused identical relaxation of noradrenaline pre-contracted arteries from both age groups. 5 Basal intracellular calcium ([Ca[sup 2+]][sub i]) was higher in SMA from aged than from adult rats. In addition, the noradrenaline [Ca[sup 2+]][sub i]-force relationship was significantly shifted to the right in the SMA from aged rats. 6 Altogether, these data indicate that responsiveness to noradrenaline is preserved both in conductance and resistance arteries with ageing. The latter results from the association of increased basal [Ca[sup 2+]][sub i], changes in Ca[sup 2+] handling at the level of thapsigargin-sensitive sarcoplasmic reticulum Ca[sup 2+]-ATPases and decreased myofilament sensitivity to Ca[sup 2+]. [ABSTRACT FROM AUTHOR]

Objective: Lipopolysaccharide (LPS) induces early (within 1 h) and delayed (after several hours) impairment of vascular reactivity to catecholamines whose mechanisms are different, although they probably both involve nitric oxide (NO). Temporal and quantitative relationships between hyporeactivity to noradrenaline and NO production were investigated in a rat model of endotoxaemia allowing to clearly distinguish the two phases of hyporeactivity. Methods: Anaesthetised rats were infused with LPS (14 mg kg−1 h−1) for 1 h. Pressure responses to noradrenaline (NA) and circulating NO derivatives (nitrosyl haemoglobin, NO2−, NO3−) were monitored for 5 h after the onset of infusion. Reactivity to NA and tissue cyclic GMP level were also assessed ex vivo, in aortic rings taken at different experimental times. Results: LPS-induced early hyporeactivity to NA was associated with a moderate but significant increase in plasma NO3− level, without any significant change in concentration of the other circulating NO derivatives. Neither reactivity ex vivo nor cyclic GMP content were modified in aortae taken after 1 h of LPS infusion. By contrast, delayed hyporeactivity (5 h after the onset of LPS infusion) was associated with a large increase in all circulating NO derivatives (up to 2.5 fold), enhanced aortic cyclic GMP level and aortic hyporeactivity ex vivo. Pre-treatment of rats with NG-nitro-L-arginine methyl ester (1 mg kg−1 i.v.) entirely prevented early hyporeactivity and rise in NO3− concentration. In addition it attenuated in comparable proportion both delayed hyporeactivity to NA in vivo and circulating levels of NO derivatives. Conclusion: The results confirm the involvement of NO in the two phases of hyporeactivity to NA induced by LPS. They strongly support the view that a circulating factor is involved in triggering endothelial NO release during the early phase, whereas the delayed phase is associated with a high production of NO in vascular smooth muscle resulting from the induction of NO synthase. [ABSTRACT FROM PUBLISHER]

Objective: Low output heart failure induces abnormalities of endothelium dependent vasodilatation, but the mechanisms responsible for this remain unclear. As blood flow can alter endothelial cell function, in particular nitric oxide (NO) release, the activity of endothelium derived relaxing factor (EDRF) was investigated in a rat model of high output heart failure. Methods: The thoracic aorta upstream of an aorto-caval fistula in rats was submitted to hormonal changes (similar to those in heart failure) and to high blood flow (opposite to that found in low output heart failure). Functional and biochemical arterial properties were studied in aorto-caval fistula rats and in sham operated rats three months after operation. The vascular responses were studied by exposing aortic segments from fistula and sham operated rats to increasing concentrations of agonists. Aortic cyclic guanosine monophosphate (cGMP) concentration was assessed as an index of NO synthase activity. The effect of NO synthase blockade on functional and biochemical arterial properties was also studied. Results: Plasma atrial natriuretic factor (ANF) was increased in fistula rats compared to sham operated rats. The concentrations of acetylcholine or the calcium ionophore A23187 required to produce 10% and 50% maximum relaxation (EC, and EC50) were similar in the two groups. Relaxation in response to low concentrations of Sin-1 (an NO donor) was shifted rightwards in fistula rats and EC10 was greater than in the controls. The aortic cGMP concentration was higher in aorto-caval fistula rats than in sham operated rats (p=0.008). The differences between aorto-caval fistula rats and sham operated rats were probably the result of increased basal EDRF-NO release in the former, since NO synthase blockade abolished the differences in both aortic cGMP and the dose-response curve to Sin-1. Conclusions: The arterial wall upstream of a chronic aorto-caval fistula has increased cGMP content and hyposensitivity to Sin-1, which may be due to enhanced basal EDRF-NO release. These changes, strikingly different from those found in the low output heart failure, suggest that haemodynamic rather than neuroendocrine factors play a determinant role in the altered vasodilator response in heart failure.Cardiovascular Research 1993;27:1651-1656 [ABSTRACT FROM PUBLISHER]

Abstract: We have previously demonstrated that in endothelium-denuded arteries, S-nitrosation of cysteine residues is a mechanism of formation of releasable nitric oxide (NO) stores, accounting for the long-lasting relaxation induced by S-nitrosating agents like S-nitrosoglutathione (GSNO). Here, we have investigated whether such effects could also be obtained in arteries exhibiting oxidative stress-associated endothelial dysfunction. Rats were implanted or not with a minipump delivering saline or angiotensin II for 14 days. As expected, aorta from angiotensin II-infused rats exhibited increased level of superoxide anions (as evaluated with dihydroethidine as fluorescent probe) and a reduced relaxation to acetylcholine in comparison to saline group. Unlike aortic rings with endothelium from controls, those from angiotensin II-infused rats exhibited persistent hyporesponsiveness to phenylephrine after pre-exposure to GSNO, as well as relaxation upon addition of N-acetylcysteine (NAC, which can displace NO from cysteine–NO residues) or HgCl2 (which cleaves S–NO bonds). In aorta from angiotensin II-infused rats, GSNO also induced a persistent increase in cysteine–NO residues (as determined using anti-cysteine–NO antiserum), which was blunted by NAC and HgCl2. These data indicate that (i) the vasorelaxant influence of releasable NO stores is unmasked by endothelial dysfunction (ii) S-nitrosation of cysteine residues remains an effective mechanism of formation of releasable NO stores in arteries exhibited oxidative stress-associated endothelial dysfunction. Thus, formation of releasable NO stores by S-nitrosating agents allows targeted vasculoprotective effects of NO at sites of endothelial dysfunction. [Copyright &y& Elsevier]

Abstract: Endothelium-independent relaxant activities of N ω-hydroxy-l-arginine (l-NOHA) homologues and hydroxylamine, a possible intermediate in nitric oxide (NO) formation, were examined in rat aortic rings. Addition of one –CH2– group to the –(CH2) x – chain between the α-amino acid and the hydroxyguanidine group (x =4) almost abolished–while deletion of one or two –CH2– (x =1 or 2) enhanced–the relaxant activity of l-NOHA homologues. N ω-hydroxy-nor-l-arginine- (x =2) and hydroxylamine-induced relaxations were blunted by a NO scavenger and by inhibitors of the guanylyl cyclase pathway, but not by NO synthase or cytochrome P 450 inhibitors (except 7-ethoxyresorufin). However, aortic NO formation was detected (using electron paramagnetic resonance) in the presence of concentrations of these compounds higher than those producing relaxation. These findings support the view that endothelium-independent vasorelaxations induced by both l-NOHA homologues with a required chain length x ≤3 and hydroxylamine are mediated by NO-dependent activation of guanylyl cyclase, through a 7-ethoxyresorufin-inhibited mechanism. [Copyright &y& Elsevier]

Hypertension has been shown to be associated with impaired endothelium-derived hyperpolarizing factor (EDHF)-mediated arterial relaxation and hyperpolarization. Treatments of hypertensive rats with inhibitors of the renin-angiotensin system have been shown to restore both EDHF-mediated responses and the expression of connexins involved in the intercellular transfer of the hyperpolarization in mesenteric arteries. The present study was designed to determine whether chronic treatment of rats with angiotensin II impairs EDHF-mediated responses and the expression of connexins in the mesenteric arterial wall. Male Wistar rats were treated with angiotensin II (0.4 mg/kg/day) for 21 days using osmotic minipumps. Arterial pressure was measured by tail-cuff plethysmography. Contractile responses and membrane potential were measured in isolated mesenteric arteries. The expression of the three connexins (Cxs), Cx37, Cx40, and Cx43, was quantified in segments of mesenteric arteries by immunohistochemistry and quantitative real-time reverse transcriptase-polymerase chain reaction. Angiotensin II administration increased the mean systolic blood pressure. EDHF-mediated relaxation and hyperpolarization to acetylcholine and red wine polyphenols were significantly impaired in mesenteric arteries from angiotensin II-treated rats in comparison with control animals, whereas nitric oxide-mediated relaxation was unaltered. The expression of connexins Cx37, Cx40, and Cx43 was significantly decreased in the mesenteric artery from angiotensin II-treated rats. These findings indicate that angiotensin II-induced hypertension is associated with a selective impairment of EDHF-mediated relaxation and hyperpolarization in the rat mesenteric artery. The inhibition of EDHF-mediated responses is due, at least in part, to a decreased expression of connexins Cx37, Cx40, and Cx43 in the arterial wall.

This study was designed to investigate the cardiovascular consequences of oral administration of Cedrelopsis grevei (CG) in normotensive rats. Experiments were designed to investigate hemodynamic parameters in vivo as well as the consequences of CG treatment on the vasoconstriction response to norepinephrine and the vasorelaxant response to ACh ex vivo in isolated aortas and small mesenteric arteries (SMA). Treatment of male Wistar rats with 80 mg/kg CG for 4 wk induced a progressive decrease in systolic blood pressure. In the aorta, CG did not significantly alter the response to norepinephrine despite the participation of extraendothelial nitric oxide (NO)-induced hyporeactivity. In the SMA, contraction to norepinephrine was not modified by CG treatment even though it enhanced the participation of endothelial NO. Endothelium-dependent relaxation to ACh was increased in both the aorta and SMA from CG-treated rats. In the aorta from CG-treated rats, the mechanism involved superoxide dismutase (SOD)- and catalase-sensitive free radical production. The latter was associated with enhanced expression of Cu/Zn SOD and endothelial NO synthase. These results suggest that oral administration of CG produces a decrease in blood pressure in normotensive rats. This hemodynamic effect was associated with enhanced endothelium-dependent relaxation and an induction of Cu/Zn SOD and endothelial NO synthase expressions in the vessel wall. They also show subtle mechanisms that compensate for the increased participation of NO to maintain unchanged agonist-induced contractility. These data provide a pharmacological basis for the empirical use of CG against cardiovascular diseases.

S-Nitrosation of cysteine residues plays an important role in nitric oxide (NO) signaling and transport. The aim of the present study was to investigate the role of S-nitrosothiols as a storage form of NO, which may account for the long-lasting effects in the vasculature. Rat aorta exposed to S-nitrosoglutathione (GSNO) displayed, even after washout of the drug, a persistent increase in cysteine-NO residues (detected by immunostaining using an antiserum that selectively recognized S-nitrosoproteins) and in NO content (detected by NO spin-trapping), a persistent attenuation of the effect of vasoconstrictors, and a relaxant response upon addition of low molecular weight (LMW) thiols. Rat mesenteric and porcine coronary artery exposed in vitro to GSNO, as well as aorta and mesenteric arteries removed from rats treated in vivo with GSNO, displayed similar modifications of contraction. In isolated aorta exposed to GSNO, the decrease of the contractile response and the relaxant effect of LMW thiols were both blunted by NO scavengers (oxyhemoglobin or 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) or by a cyclic GMP-dependent protein kinase inhibitor (Rp-8-bromoguanosine-3',5'-cyclic monophosphorothioate). In these arteries, mercuric chloride (which cleaves the cysteine-NO bond) exerted a transient relaxation, completely abolished the one of LMW thiols, and blunted the increase in cysteine-NO residues and NO content. Together, these data support the idea that S-nitrosation of cysteine residues is involved in long-lasting effects of NO on arterial tone. They suggest that S-nitrosation of tissue thiols is a mechanism of formation of local NO stores from which biologically active NO can subsequently be released.

The mechanisms of vasorelaxation elicited by N(omega)-hydroxy-L-arginine (L-NOHA) and other compounds bearing a C=NOH function and the structural determinants governing this effect were investigated in rat aorta. L-NOHA, formamidoxime, five aromatic monosubstituted amidoximes, and one aromatic monosubstituted ketoxime elicited relaxation in endothelium-denuded rings. N-Hydroxyguanidine and substituted N-hydroxyguanidines were markedly less active. Relaxations induced by L-NOHA and by the most active studied compound, 4-chlorobenzamidoxime (ClBZA), were unmodified by the presence of endothelium. In endothelium-denuded rings, they were blunted by the NO scavenger 2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide (300 microM) and by the inhibitor of guanylyl-cyclase activation 1H[1,2,4,]oxadiazolo[4,3-a]quinoxalin-1-one (1 microM). In addition, L-NOHA- and ClBZA both caused cGMP accumulation. L-Arginine, but not D-arginine (1 mM), antagonized the effect of L-NOHA but not ClBZA. Both L-NOHA- and ClBZA-induced relaxations were inhibited by the NAD(P)H-dependent enzymes inhibitor diphenyliodonium (30 microM) and the NAD(P)H-dependent reductases inhibitor 7-ethoxyresorufin (10 microM), but they were unmodified by the cytochrome P450 (P450) inhibitor proadifen (10 microM) and by the NO synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME, 300 microM). These results show that L-NOHA and other compounds with a C=NOH function can cause endothelium-independent relaxation in the rat aorta. They suggest that activation of guanylyl cyclase and NO formation is implicated in relaxation and that a 7-ethoxyresorufin-sensitive NAD(P)H-dependent pathway is involved. On one hand, L-NOHA and amidoximes may be useful tools for characterizing this pathway in blood vessels and, on the other, may offer a novel approach for treating vascular diseases with impaired endothelial NO activity.