Effects of prostaglandins on the adenylate cyclase activity of lungs from fetal rabbits.

Abstract

Prostaglandin E1 (PGE1) and PGI2 stimulate adenylate cyclase activity in lungs from fetal rabbits (29 days of gestation) with EC50 values of 4.4 and 2.6 X 10(-7) M, respectively. PGE2, PGD2, PGF2 alpha, and 6-oxoPGF1 alpha are active only at much higher concentrations. The response of adenylate cyclase to PGE1 rises gradually from 16% to 60% above basal between days 21-26 of gestation. Between days 26-27 of gestation, there is a sharp increase in stimulated activity to 120% above basal (P < 0.001). This level is maintained until 3 days after birth. A further increase was observed 8 days after birth. Stimulation of adenylate cyclase by fluoride increases gradually from about 100% to nearly 400% above basal activity between 21 days of gestation and 8 days after birth. During this time there are no significant changes in basal activity. The increased response of adenylate cyclase to PGE1 between days 26-27 of gestation occurs at a time when unbound plasma cortisol and synthesis of pulmonary surfactant start to increase in the fetal rabbit. It is possible that cortisol sensitizes adenylate cyclase to prostaglandins, which could explain some of the its actions on surfactant synthesis.