Concentrations of renin and renin substrate in plasma of rabbits during pregnancy and the post partum period.

Abstract

The content of renin in rabbit uterus is known to increase many fold during pregnancy followed by a rapid fall to normal levels within a few days after delivery. In order to study this mechanism the blood concentrations of renin and its substrate were measured. Contrary to the concentration of renin in uterus, the plasma renin concentrations were not increased either during pregnancy or in the post partum period. The renin-substrate concentration was unchanged during the first part of pregnancy but was increased 2–3-fold in the days around delivery. This increase resulted in a corresponding increase in plasma renin activity. It was concluded that the rapid inactivation of uterine renin post partum was due to a local inactivation and not to a release of renin to the blood.