Kininogen, esterase and kininase activities in human peripheral venous plasma and in plasma from the intervillous space of human placenta, before and during labor.

Kininogen, esterase and kininase activity were measured in the peripheral venous and intervillous placental plasma of women submitted to cesarean section and of women who delivered normally. Kininogen consumption occurred in the intervillous placental plasma during labor. Kininase activity increased in the intervillous placental plasma during labor and was considerably higher than in peripheral venous plasma. Esterase activity was high during labor and decreased after delivery.