Plasma renin activity and cAMP in termination of pregnancy induced by sulprostone

Plasma renin activity (PRA), plasma concentrations of cyclic adenosine-3',5'-monophosphate (cAMP) and the serum levels of oestradiol, progesterone, chorionic gonadotrophin, potassium, sodium and calcium were estimated in connection with termination of pregnancy induced in 23 women by sulprostone, a derivative of prostaglandin E2. A rapid decrease in PRA was observed during and after infusion of 1000 micrograms or 1500 micrograms sulprostone. PRA returned to the initial values at 24 h after drug administration. The lowest levels of PRA were 36% and 51% of the initial values (P less than 0.001) in the two drug concentration groups. No significant changes were observed in the control group. The value for plasma cAMP did not correspond completely to the changes in PRA. Serum concentrations of oestradiol, progesterone and chorionic gonadotrophin showed a gradual decrease during drug administration. The changes in serum potassium, sodium and calcium were minimal. The decrease in PRA associated with sulprostone is very surprising. Our finding elucidates in part the still rather poorly known mechanisms and function of renin-angiotensin system in pregnancy.