Are the renal functional changes of human pregnancy caused by prostacyclin?

To investigate the hypothesis of others that the many characteristic physiological alterations of pregnancy are due to prostacyclin, the effects of this vasodilator prostaglandin on renal function and related variables were measured. Intravenous infusion of prostacyclin (7 ng/kg/min) for 90 minutes in seven healthy male volunteers resulting in a significant fall in diastolic blood pressure and increase in heart rate. No significant change occurred in renal plasma flow or glomerular filtration rate in response to the prostacyclin, but there were significant falls in uric acid clearance (16 +/- 1.3----10 +/- 1.5 ml/min/ 1.73m2) and in free water clearance (4.0 +/- 1.1-----0.5 +/- 0.4 ml/min) both of which rose rapidly to pre-infusion levels upon cessation of prostacyclin infusion. Plasma renin and aldosterone levels rose sharply during prostacyclin infusion, falling to pre-infusion levels rapidly afterwards. Although the haemodynamic alterations were similar, the renal functional effects of prostacyclin infusion were quite different from (and often opposite in direction to) those of normal pregnancy. This acute study therefore does not add support to the hypothesis suggested by others that these alterations in pregnancy are due to prostacyclin, and that deficiency of prostacyclin will lead to the changes of pregnancy-associated hypertension.