Endothelins and membrane potential of vascular smooth muscle of the canine coronary artery

Abstract

We investigated the effects of endothelins on the membrane potential of vascular smooth-muscle cells of canine coronary artery, using glass microelectrodes. In tissues with endothelium, endothelin-1 (ET-1), from 10- 12 to 10-9 M, did not alter the membrane potential. Higher concentrations of the peptide produced sustained depolarization without detectable hyperpolarization. Endothelin-3 (ET-3, 10-11 to 10-8 M) did not produce significant membrane hyperpolarization in tissues with endothelium. Prostaglandin F(2α) (10-5 M) depolarized the cell membrane by about 6 mV. ET-1 (10-9 M) did not evoke detectable hyperpolarization in the presence of prostaglandin F(2α). In tissues incubated with BQ123 (10-6 M, a selective ET(A)-receptor antagonist), which attenuated the depolarization evoked by ET- 1, both isopeptides did not produce detectable hyperpolarization. These findings suggest that ET-1 and ET-3 do not evoke the release of endothelium- derived hyperpolarizing factor in the canine coronary artery.