Concentrations of oestrogens and progesterone in the plasma of ovariectomized and ovariectomized Norgestrel-treated pregnant guinea-pigs.

Abstract

Summary. Ovariectomy and/or adrenalectomy of guinea-pigs did not significantly affect the plasma concentration oftotal unconjugated oestrogens throughout pregnancy when compared to intact animals. This indicates that oestrogen production in the pregnant guinea-pig is predominantly extra-ovarian. The plasma concentrations of progesterone in animals ovariectomized between Day 3 and Day 5 post coitum (p.c.) and treated with Norgestrel to maintain pregnancy increased appreciably only after Day 30 p.c., and rose to levels not significantly different from those in animals ovariectomized later in pregnancy or in intact controls. This confirms the findings of other workers that the secretion of progesterone by extra-ovarian sites (the placentae) is important only during the second half of gestation. In Norgestrel-treated animals, masculinization of the maternal external genitalia was not seen during pregnancy but developed within 5 days after parturition.