Renin substrate, active and acid-activatable renin concentrations in human plasma and endometrium during menstrual cycles controlled by oral contraceptive preparations.

Measurements of active and acid-activatable renin concentrations and renin substrate concentrations in plasma and endometrial samples taken from 31 patients are described. All of these patients were taking oestrogen-containing oral contraceptive preparations. Plasma active renin concentration was lower in these cycles than in normal cycles and the substrate concentrations higher. In the endometrium the concentrations of all of the components of the system were raised by oral contraceptives. As with normal cycles, the maximum potential for production of the angiotensins was in the premenstrual stage of the cycle. It is suggested that this increase in potential is associated with the onset of menstruation.