Endothelin-1 as an Autocrine Growth Factor for Endothelial Cells

To elucidate the role of endothelin-1 (ET-1) as an autocrine growth factor for vascular endothelial cells (ECs), we studied the effects of phosphoramidon, an inhibitor of ET-1-converting enzyme, on the production of ET-1-like immunoreactivity (LI), [125I]ET-1 binding activity, ETB receptor mRNA expression, phosphoinositide breakdown, and DNA synthesis in cultured bovine carotid artery ECs. Phosphoramidon dose-dependently decreased ET-1-LI production but reciprocally increased [125I]ET-1 binding capacity. ET-1 and ET-3 equipotently inhibited the binding of [125I]ET-1 only in the presence of phosphoramidon. Northern blot analysis revealed that ETB receptor mRNA expression was more evident in phosphoramidon-treated cells than in nontreated cells. In the presence of phosphoramidon, ET-1 and ET-3 equipotently stimulated inositol 1,4,5-trisphosphate formation and [3H]-thymidine incorporation into cultured ECs. Both phosphoramidon and anti-ET-1 antibody inhibited basal [3H]thymidine incorporation. These data suggest that endogenous ET-1 constitutively secreted by ECs is an autocrine growth factor via ETB receptors.