Role of Phosphoinositide Turnover and Cyclic AMP Accumulation in Prostaglandin-Stimulated Noradrenaline Release from Cultured Adrenal Chromaffin Cells

Prostaglandins (PGs) E1, E2 and F2a stimulated release of nor-adrenaline from chromaffin cells; the most potent was PGF2a with an ECro of about 0.1 M. The rank order of potency for release, and the ECso for each PG, was the same as that for stimulation of (poly)phosphoinositide turnover. PGE1-stimulated release was dependent on extracellular calcium and sensitive to dihydropyridine calcium channel agonists and antagonists at 1 M, but unlike release stimulated by 50 mM extracellular potas-sium was not sensitive to verapamil or diltiazem at 1 0 zM. The PGs also enhanced the turnover of inositol ptiospholipids, but the PGE1-stimulated formation of inositol phosphates was small compared to that produced by bradykinin, which stimulates a similar degree of release. Unlike release, the stimulation of mo-sitol phosphate formation by PGs was not dependent on th