The effects of intracellular Ca2+ concentration and hypoxia on basal endothelin-1 secretion by cultured porcine aortic endothelial cells.

When the intracellular free Ca2+ concentration ([Ca2+]i) of porcine aortic endothelial cells incubated in normoxic or hypoxic atmosphere was varied more than tenfold, basal endothelin-1 (ET-1) secretion was maximal at control conditions ([Ca2+]i = 190 nM) and reduced at lower and higher [Ca2+]i. High [Ca2+]i reduced ET-1 synthesis only in part via activation of the NO/cGMP system. Our results provide evidence that basal ET-1 secretion is regulated by [Ca2+]i, and that Ca2+ plays a similar role in hypoxic and normoxic signal transduction.