Abstract
Endothelin-1 (ET-1) is reported to be the most powerful constrictor of blood vessels known. Atrial natriuretic factor is a potent relaxor of contracted vessels. This study examined the potential interaction between these vasoactive peptides on rabbit aortic rings. ET-1 contracted the rings in a dose-dependent manner with an ec 50 (-log M) of 9.78 ± 0.16. Atriopeptin III (APIII) completely relaxed ET-1 (10 −9 M)-contracted rings with an EC 50 of 9.63 ± 0.07 and methoxamine contracted rings with an EC 50 of 9.18 ± 0.09. Pretreatment of aortic rings with APIII (up to 3 × 10 −6 M) did not alter the normal ET-1 dose-response curve with respect to potency but did diminish the maximal contraction achieved. An interesting additional finding was that the temporal nature of ET-1-induced contraction is remarkably dose-variable. In conclusion, the potent contractile effects of ET-1 on vascular smooth muscle can be effectively reversed but not prevented by APIII.
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