Abstract
To clarify the mechanisms underlying the vasoactive effects of endothelin-3 (ET-3), we examined the effects of indomethacin, endothelium-denudation, methylene blue and L-NG-monomethyl arginine (L-NMMA) on the perfusion pressures of isolated rat mesenteric arteries infused with ET-3. ET-3 at 10-15 10-8 M elicited significant vasodilations in a dose-related manner, in which 10-9 and 10-8 M ET-3 caused biphasic pressure changes involving a transient dilation and subsequent vasoconstriction. Five micromolar indomethacin did not affect the vasodilations and vasoconstrictions induced by ET-3. In endothelium-denuded arteries, 10-13-10-8 M ET-3 elicited significant vasoconstriction in a dose-related manner without any vasodilation. In the presence of 30μM methylene blue, the vasodilations induced by ET-3 disappeared. In the presence of 100μM L-NMMA, 10-15-10-8 M ET-3 elicited significant vasoconstrictions in a dose-related manner, and the vasodilation by ET-3 existed only at 10-8M ET-3. These data suggest that the vasodilating effects of low doses of ET-3 through the endothelium overcome the vasoconstricting effects, and that the vasodilating effects of ET-3 are associated with an endothelium-derived relaxing factor as an endothelium-derived nitric oxide.
