Endothelin Dissociates Muscle Tension from Cytosolic Ca2+ in Vascular Smooth Muscle of Rat Carotid Artery

Abstract

Endothelin induced rapid increase followed by a decrease in cytosolic Ca2+ ([Ca2+]i) and a slow increase in muscle tension in the vascular smooth muscle strip of rat carotid artery. Thus, the endothelin-induced contraction was smaller, and it became gradually greater than high K-induced contraction at a given ([Ca2+]i). In Ca2+ -free solution, endothelin induced a transient increase in ([Ca2+]i) and a sustained contraction. These results suggest that endothelin-induced contraction is due to the increase in ([Ca2+]i), the time-dependent change in Ca2+ -sensitivity of contractile elements, and the mechanism which is independent of the increment in ([Ca2+]i).