Gestational age-related inhibition of placental hCG, alpha hCG and steroid hormone release in vitro by a GnRH antagonist.

Human placental tissues have been shown to contain gonadotrophin-releasing hormone-(GnRH)-like activity. Thus, the effect of a potent GnRH antagonist (N-Ac-Pro1,D-p-Cl-Phe2,D-Nal(2)3,6-GnRH, obtained from Syntex Laboratories) on placental hormonal release was studied. Explant cultures of placentae of 6 to 15 weeks' gestation were studied. This GnRH antagonist did not inhibit the alpha human chorionic gonadotrophin (alpha hCG), human chorionic gonadotrophin (hCG), oestrone or oestradiol release from the six- and nine-week placental cultures, but greatly suppressed the release of these hormones in the placental cultures from 13- and 15-week gestations. Synthetic GnRH partially reversed the action of this antagonist on the hormonal releases in the 15-week placental cultures. These data demonstrate a gestational age-related action of this antagonist on placental hormonal release. Thus, a role for the endogenous GnRH-like activity of the placenta in the control of placental hormonogenesis is indicated.