Contractile effect of endothelin in the human uterine artery and autoradiographic localization of its binding sites.

Abstract

The aim was to study the effects, mode of action, and binding sites of endothelin-1 in the human uterine artery. The contractile effect of endothelin-1 on the human uterine artery with and without endothelium and the effect of verapamil and nicardipine on the contraction was investigated in vitro. The Student t test was used. Iodine 125-endothelin-1 binding sites were localized with autoradiography. Endothelin-1 induced a contraction that was unaffected by removal of the endothelium. Verapamil antagonized the contraction, whereas nicardipine showed no effect. Iodine 125-endothelin-1 binding sites were demonstrated in the smooth muscle layer. These results show that endothelin-1 is a vasoconstrictor in the human uterine artery and suggest that the effect is mediated by receptors on the smooth muscle cells. The mode of action seems to involve Ca++ influx by other than dihydropyridine-sensitive Ca++ channels. Endothelin-1 does not seem to stimulate release of other endothelium-derived vasoactive agents.