Plasma renin and kallikrein in parturient women and newborn babies.

There are changes in both the plasma renin system and plasma kallikrein system during parturition. To investigate the interrelationship between plasma inactive renin and plasma kallikrein, we measured plasma active renin, inactive renin, active kallikrein and inactive kallikrein in 21 parturient women just before delivery and on the 5th day after delivery, and also in 30 newborn babies upon birth and on the 5th day after birth. Plasma active renin was measured by radioimmunoassay of angiotensin I generated after the addition of an exogenous substrate. Inactive renin was activated by trypsin. Active kallikrein was measured by kallikrein activity on substrate S-2302. Inactive kallikrein was activated by an activator containing the Hageman factor and kininogen. The results showed a significant decrease in active renin, inactive renin, and a significant increase in active kallikrein, inactive kallikrein and the active/total kallikrein ratio in mothers on the 5th day after delivery. In vaginally delivered babies, a decrease in active renin and in the active/total renin ratio were observed on the 5th day after birth, but inactive renin, active and inactive kallikrein showed no change. In babies delivered by cesarean section, no change in either the renin or kallikrein level was found. The patterns of change in plasma active renin and inactive renin in mothers and babies are in keeping with previous suggestions that plasma inactive renin is prorenin. There was no correlation between the plasma active/total renin ratio or the plasma active kallikrein level in mothers and babies, either before or after delivery.(ABSTRACT TRUNCATED AT 250 WORDS)