Prostaglandin biosynthesis and its compartmentation in vascular smooth muscle and endothelial cells.

PGI2 is the major, if not the only, eicosanoid formed by smooth muscle and endothelial cells of large arteries and veins. PGI2 is not the major prostanoid synthesized by microvessels. Different stimuli elicit prostanoid production by smooth muscle and endothelial cells. PGI2 is formed at several subcellular sites within smooth muscle and perhaps endothelial cells, but the consequences of this highly unusual distribution are unknown. PGI2 formed by the endothelium can exit on the luminal surface to modulate the functions of circulating blood cells, and probably on the abluminal surface to relax underlying smooth muscle. PGI2 formed by smooth muscle probably acts only upon smooth muscle cells.