Angiotensin Converting Enzyme and Angiotensin Stimulated Prostanoid Production in the Umbilical Artery in Preeclampsia

Abstract

Angiotensin Converting Enzyme (ACE) activity was measured in maternal and fetal blood samples from preeclamptic and normotensive pregnancies and in samples from non-pregnant women. The enzyme activity was found to be significantly higher in the hypertensive pregnancies. For all pregnancies the levels in the umbilical venous samples exceeded those in the arterial samples.

The vascular production of prostacyclin and thromboxane was investigated by in vitro perfusion of umbilical arteries from these pregnancies. Both angiotensin I and II elicited significant changes in the production, giving an increased prostacyclin/thromboxane ratio. In the hypertensive pregnancies the arteries displayed a lower production rate, and the angiotensin-induced changes were smaller, especially those of angiotensin I.

The results indicate that preeclampsia also involves circulatory changes in the fetus, and that the vascular angiotensin I-conversion might be reduced despite higher circulating activity of the converting enzyme.