CELLULAR MECHANISM OF ENDOTHELIN-INDUCED NITRIC-OXIDE SYNTHESIS BY CULTURED BOVINE ENDOTHELIAL-CELLS

Endothelins (ETs) cause initial and transient vasodilation via an endothelium-dependent mechanism. We studied the cellular mechanism by which ETs stimulate synthesis and release of endothelium-derived relaxing factor (EDRF)/nitric oxide (NO) in cultured bovine endothelial cells (EC). ET-1 and ET-3 rapidly (within 1 min) and dose-dependently (10(10) to 10(-7) M) stimulated production of nitrate/nitrite (NOx) in bovine EC; ET-3 was more potent than ET-1 at generating endothelial NOx. The ET3-stimulated NOx production was completely abolished by a NO synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA), the effect of which was reversed by coadministration of exceSS L-arginine. NOx production stimulated by ET-3 was blocked by an intracellular Ca2+ chelator but not by an extracellular Ca2+ chelator. A selective calmodulin inhibitor W-7 dose-dependently inhibited the ET-3-stimulated NOx production, whereas a nonselective calmodulin inhibitor W-5 failed to affect NOx production. These data suggest that ETs stimulate receptor-mediated EDRF/NO synthesis via a Ca2+/calmodulin-dependent pathway in vascular endothelial cells.