Lack of endothelin ETB receptor-mediated smooth muscle hyperpolarization in rat mesenteric resistance arteries.
The presence of functional endothelin ETB receptors was investigated in rat isolated mesenteric resistance arteries. Neither endothelin-3 (0.1-100 nM) nor the endothelin ETB selective agonists sarafotoxin S6c and BQ 3020 (both 1-100 nM) induced any measurable hyperpolarization or relaxation in stimulated (alpha 1-adrenoceptor agonist; phenylephrine) or unstimulated arteries. In both cases, the subsequent addition of acetylcholine (1 microM) hyperpolarized the membrane potential by 10-20 mV and totally reversed any contraction which was present. These results indicate that the endothelin ETB-mediated vasodilatation observed in the intact mesenteric bed does not reflect hyperpolarization of smooth muscle cells in resistance arteries arising from the mesenteric artery.
Waldron
G J
GJ
Department of Pharmacology, University of Bristol, University Walk, UK.
Roach
A G
AG
Garland
C J
CJ
D000818:Animals; D019334:Endothelin-3 / Q000494:pharmacology; D016232:Endothelins / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008638:Mesenteric Arteries / Q000502:physiology*; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D010446:Peptide Fragments / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D017466:Receptors, Endothelin / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014757:Viper Venoms / Q000494:pharmacology
D019334:Endothelin-3; D016232:Endothelins; D010446:Peptide Fragments; D017466:Receptors, Endothelin; D014662:Vasoconstrictor Agents; D014757:Viper Venoms; C057354:sarafotoxins s6; C075771:BQ 3020