Changes in plasma renin activity (PRA), angiotensin I and placental leucine aminopeptidase (P-LAP) activity during normal pregnancy.

Plasma renin activity (PRA) and relative changes in angiotensin I compared with non-pregnant women were determined by radioimmunoassay (RIA) at different stages of normal gestation. Their levels showed increases in the early and late stages, and decreases at the period of 25 to 28 weeks of pregnancy in the middle stage, although their levels were higher than those in non-pregnant women throughout pregnancy. The increase in angiotensin I was less striking than that of PRA. Placental leucine aminopeptidase (P-LAP) activity increased progressively with advancing gestation, reaching the highest value at the 38th week of pregnancy. Simultaneous estimations of changes in angiotensin I and placental leucine aminopeptidase (P-LAP) were performed longitudinally in 12 normal pregnant women. The significance of the increase in P-LAP activity and the relationships among PRA, angiotensin I and P-LAP during normal pregnancy are discussed.