PLASMA STEROIDS, PROLACTIN AND PLACENTAL-LACTOGEN IN INTACT OR HYPOPHYSECTOMIZED PREGNANT EWES WITH AN HYPOPHYSECTOMIZED FETUS - EFFECT OF FETAL PERFUSION OF DEXAMETHASONE

Progesterone, total estrogens (mainly conjugated and unconjugated estrone), prolactin and placental lactogen have been determined during late pregnancy in the peripheral plasma of intact or hypophysectomized ewes after destruction of the fetal pituitary. During the prolongation of gestation due to the removal of the fetal hypophysis, progesterone and placental lactogen remained at a high level, while total estrogens and prolactin maintained a low concentration. When the fetus was perfused for 2 days with dexamethasone, the induced lambing was preceded by a fall in progesterone concentrations followed by a decrease in placental lactogen; at the same time, an abrupt increase in estrogens and prolactin was observed.