PROGESTERONE IN SYSTEMIC BLOOD AND PLACENTAE OF INTACT AND OVARIECTOMIZED PREGNANT GUINEA-PIGS

Abstract

SUMMARY Progesterone was isolated from systemic and uterine venous plasma and from placental tissue of intact and ovariectomized pregnant guinea-pigs. It was measured quantitatively by fluorescence assay. Concentrations of progesterone in intact animals rose from a mean value of 64 ng./ml. plasma 11–16 days post coitum (p.c.) to reach their highest values (265 ng./ml.) 30–45 days p.c. and decreased to 140 ng./ml. immediately before parturition. In pregnant guinea-pigs, ovariectomized 28 days p.c. or later, the progesterone levels were lower (75 ng./ml. at 34–35 days p.c., 146 ng./ml. at 40–45 and 50–55 days p.c.) except at the end of pregnancy (165 ng./ml.). During the last 2 weeks of pregnancy the difference in the progesterone levels of the two groups was not statistically significant. In ovariectomized pregnant guinea-pigs, the progesterone level was high in the uterine vein but low in placental tissue. The mean wet weight of placentae was, however, significantly correlated with systemic progesterone values.