Release of inactive renin from human fetal membranes and isolated trophoblasts

Human chorio-amnion from term pregnancy was perfused in vitro in a dual perfusion apparatus. Renin released from the fetal membranes was almost entirely in the form of inactive renin (IR) (trypsin-activated). IR was released from both the chorion side and the amnion side. IR introduced on the chorion side of the chorio-amnion did not appear on the amnion side. When cells isolated from term amnion and chorion were grown in tissue culture, IR was released continuously from chorionic cells but not from amnionic cells. The release of IR did not parallel the release of LDH from cultured chorion cells. Exposure to low calcium medium (with or without EGTA) decreased IR release while LDH release increased (or remained constant). Exposure to the calcium ionophore (A 23187) resulted in a marked decrease in IR release. The release of IR from chorionic cells shows some similarities to the release of HCG from trophoblasts. It is expected that IR release from the chorion will show some similarities to R release from the kidney as well as major differences. The function, regulation, and processing of chorionic IR remain to be elucidated.