Renin in the uterus of pregnant mice. Immunocytochemical, ultrastructural and biochemical studies.

The distribution and content of renin in the uterus of pregnant mice (12--14 days of gestation) was studied by immunocytochemistry, electron microscopy and radioimmunoassay. The uterine renin concentration at this stage of pregnancy was four-fold higher than that of the nonpregnant uterus but still less than 0.1% of the kidney renin concentration. Renin was localized almost exclusively in the decidual and entodermal epithelial linings of the yolk sac (uterine) cavity near the marginal sections of the placenta. By electron microscopy granular and vesicular structures were observed in the renin containing epithelial cells. Chorioallantoic placenta, myometrium, decidua basalis and the antimesometral parts of the epithelial leafs of the uterine cavity did not contain renin. The specific localization of renin suggests a role in parturition or delivery of the placenta.