[Effect of inhibitors of sodium-calcium exchangers on acetylcholine-induced hyperpolarization of endothelial cells in rat aorta].

The effect of selective sodium-calcium exchanger blockers on acetylcholine-induced hyperpolarization of endothelial cells from excised rat aorta was investigated. Acetylcholine administration induced sustained endothelial hyperpolarization. In the presence of 100 microM benzamil, the blocker of forward and reversed mode of the exchanger, acetylcholine induced only short-lived hyperpolarization. When benzamil was introduced during the plateau phase of hyperpolarization the amplitude of hyperpolarization significantly and reversibly decreased. KB-R7943 (20 microM), the blocker of reversed sodium-calcium exchanger, exerted the similar effect. Benzamil-mediated inhibition of sustained hyperpolarization was observed when recordings were commenced from isolated endothelium. The results obtained suggest that reversed mode of sodium-calcium exchanger is activated in intact endothelial cells following stimulation by acetylcholine.