Changes in angiotensin-converting enzyme during pregnancy in the guinea pig

Angiotensin-converting enzyme (ACE) activity was measured weekly in plasma of pregnant guinea pigs either during the last half of pregnancy (experiment 1) or throughout pregnancy (experiment 2). ACE activity increased about the time of the first missed estrus, reached a maximum about days 35-40, and then declined. A similar rise and decline in plasma ACE activity does not appear to have been reported in other animals or in humans.