Nitric oxide relaxes the vascular smooth muscle independently of endothelin-1- and U46619-induced intracellular increase of calcium.
A balance between circulating and locally released vasoconstrictors, such as endothelin-1 (ET-1), and vasodilators, such as nitric oxide, controls vascular smooth muscle tone. In the study reported here, using the technique of simultaneous measurements of intracellular free calcium ([Ca2+]i) and tension, we investigated the effects of a nitric oxide donor, sodium nitroprusside (NaNP) on endothelin-1- and U46619- [a thromboxane angiotensin-II (TXA-II) mimetic] induced sustained increases in tension and [Ca2+]i in intact and endothelium-denuded rabbit thoracic aortas. Our results showed that, in both intact and endothelium-denuded preparations, the nitric oxide donor NaNP (10(-6) M) reverses the ET-1- (10(-7) M) and U46619- (10(-7) M) induced sustained increase in tension but not in [Ca2+]i. However, it did not reduce the ET-1- and U46619-induced responses. Our data suggest that nitric oxide production modulates vascular smooth muscle tension via a mechanism that is independent of that generated by vasoconstrictors such as ET-1 and TXA-II.
Bkaily
G
G
Department of Anatomy and Cell Biology, Faculty of Medicine, University of Sherbrooke, Québec, Canada. gbkail01@courrier.usherb.ca
Shbaklo
H
H
Taoudi-Benchekroun
M
M
Sader
S
S
Duval
M
M
Jacques
D
D
D'Orléans-Juste
P
P
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D006152:Cyclic GMP / Q000502:physiology; D019332:Endothelin-1 / Q000494:pharmacology*; D005260:Female; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D009599:Nitroprusside / Q000494:pharmacology; D011817:Rabbits; D014664:Vasodilation / Q000187:drug effects*
D019332:Endothelin-1; D009599:Nitroprusside; D009569:Nitric Oxide; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D006152:Cyclic GMP; D002118:Calcium; D019331:NG-Nitroarginine Methyl Ester