Binding of prostaglandin E 2 to cultured bovine adrenal chromaffin cells and its effect on catecholamine secretion

Abstract

We have previously shown that plasma membranes from adrenal medulla possess specific high-affinity binding sites for prostaglandins (PGs) E 1 and E 2. We have now investigated the binding of PGE 2 to intact bovine adrenal chromaffin cells and the effects of prostaglandins on the release of catecholamines from these cells. Adrenal chromaffin cells specifically bound PGE 2 with a dissociation constant of 2 nM and a concentration of about 40 000 binding sites per cell. Low concentrations of PGE 2 inhibited the nicotine-stimulated release of catecholamines from these cells. The effect of PGE 2 was biphasic, the maximal inhibitory effect being observed at a concentration of between 1 and 10 nM. Higher concentrations (1 μM) of PGE 2 had minimal inhibitory effects on nicotine-evoked noradrenaline release, but instead had a direct stimulatory effect in the absence of cholinergic agonists. Although the stimulatory effects of high concentrations of PGE 2 were reproducibly observed in all cell preparations, only about one-half of the cultures tested responded to the inhibitory effects of this prostaglandin. It is possible that PGE 2 plays a modulatory role in the regulation of catecholamine secretion from the adrenal medulla.