Role of ET(A) receptors in the regulation of vascular reactivity in rats with congestive heart failure.
Endothelium-derived nitric oxide (NO) and endothelin (ET)-1 interact to regulate vascular tone. In congestive heart failure (CHF), the release and/or the activity of both factors is affected. We hypothesized that the increased ET-1 production associated with CHF may result in a reduced smooth muscle sensitivity to NO. The aim of this study was to evaluate the effects of a chronic treatment with the ET(A)-receptor (ET receptor A) antagonist LU-135252 (LU) on cerebrovascular reactivity to sodium nitroprusside (SNP) in the rat infarct model of CHF. Rats were subjected to coronary artery ligation and were treated for 4 wk with placebo (n = 24) or LU (50 mg. kg(-1). day(-1), n = 29). CHF was associated with a decreased (P < 0.05) efficacy of SNP to induce relaxation of isolated middle cerebral arteries. Furthermore, neither NO synthase inhibition with N(omega)-nitro-L-arginine (L-NNA) nor endothelial denudation affected the efficacy of SNP. Thus the endothelium no longer influences smooth muscle sensitivity to SNP. LU treatment, however, normalized (P < 0.05) smooth muscle sensitivity to SNP. Sensitivity of ET-1-induced contraction was increased in CHF only in the presence of L-NNA, whereas contraction induced by ET(B) receptor (receptor B) stimulation was increased (P < 0.05) in endothelium-denuded vessels. LU treatment restored these changes in reactivity and revealed a significant endothelium-dependent ET(B)-mediated relaxation after NO synthase inhibition. In conclusion, CHF decreases and uncouples cerebrovascular smooth muscle sensitivity to SNP from endothelial regulation. The observation that chronic ET(A) blockade restored most of the changes associated with CHF suggests that activation of the ET-1 system importantly contributes to the alteration in vascular reactivity observed in experimental CHF.
Thorin
E
E
Département de Chirurgie et, Centre de Recherche, Institut de Cardiologie de Montréal, Montréal, Quebec H1T 1C8, Canada. thorin@icm.umontreal.ca
Lucas
M
M
Cernacek
P
P
Dupuis
J
J
D000818:Animals; D002536:Cerebral Arteries / Q000187:drug effects* / Q000502:physiology / Q000503:physiopathology; D004562:Electrocardiography; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1 / Q000097:blood / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000502:physiology / Q000503:physiopathology; D006333:Heart Failure / Q000209:etiology / Q000503:physiopathology*; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000503:physiopathology*; D009203:Myocardial Infarction / Q000503:physiopathology*; D019335:Nitroarginine / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D010666:Phenylpropionates / Q000494:pharmacology*; D011743:Pyrimidines / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*; D014757:Viper Venoms / Q000494:pharmacology
D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; D010666:Phenylpropionates; D011743:Pyrimidines; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin; D014662:Vasoconstrictor Agents; D014757:Viper Venoms; C057354:sarafotoxins s6; D009599:Nitroprusside; D019335:Nitroarginine; C107831:darusentan