Regional vasodilation to endothelin-1 is mediated by a non-ETA receptor subtype in the anaesthetized rat: effect of BQ-123 on systemic haemodynamic responses.
The sustained infusion of 75 nmol/kg per min BQ-123 selectively attenuates the systemic pressor responses to i.v. bolus endothelin-1 in the anaesthetized rat; the initial systemic vasodepression is only attenuated when a 10-fold higher dose of this ETA-selective antagonist is infused. These doses of BQ-123 do not antagonize the haemodynamic actions of angiotensin II or calcitonin gene-related peptide nor do they alter basal systemic haemodynamics. The secondary increase in carotid vascular resistance associated with the systemic pressor actions of endothelin-1 is selectively attenuated by the bolus i.v. administration of BQ-123 (1.6 mumol/kg); the maximum degree of the vasorelaxation that precedes this more sustained constriction is unaltered. Thus, the initial carotid vasodilation observed to endothelin-1, and the associated systemic vasodepression, is mediated by a non-ETA receptor subtype. Furthermore, subtle differences might exist between the receptors mediating mesenteric and carotid vasoconstriction since only the latter is sensitive to BQ-123.
Douglas
S A
SA
Department of Cardiovascular Pharmacology, SmithKline Beecham Pharmaceuticals, King of Prussia, PA 19406-0939.
Elliott
J D
JD
Ohlstein
E H
EH
D000758:Anesthesia; D000818:Animals; D016232:Endothelins / Q000494:pharmacology*; D006439:Hemodynamics / Q000187:drug effects*; D008297:Male; D010456:Peptides, Cyclic / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017466:Receptors, Endothelin / Q000187:drug effects / Q000502:physiology*; D014664:Vasodilation / Q000187:drug effects*
D016232:Endothelins; D010456:Peptides, Cyclic; D017466:Receptors, Endothelin; C072247:cyclo(Trp-Asp-Pro-Val-Leu)