Sodium ions discriminate between stimulatory and inhibitory effects of prostaglandin E2 on human fat cell adenylate cyclase

Prostaglandin E2 (PG E2) has biphasic effects on human fat cell adenylate cyclase with inhibition occurring in the nanomolar concentration range and stimulation at PG E2-concentrations above 1 mumol/l. Sodium ions stimulate the human fat cell adenylate cyclase in a hormone-like manner. The inhibitory component of PG E2-action is markedly augmented by sodium ions. In addition, the monovalent cation, by interfering with the stimulatory component of PG E2 discriminates between the opposing effects of PG E2 suggesting that the antagonistic effects of the E-type prostaglandins are mediated through distinct processes.