Dexamethasone increases inhibin and estradiol secretion mediated by endogenous FSH in equine chorionic gonadotropin (eCG)-primed immature female rats

In the present study, we have examined whether the effects: of dexamethason e on follicle stimulating hormone (FSH) secretion were mediated by hypophys iotropic factors, and whether the increased levels of FSH induced by dexame thasone can stimulate ovarian functions in equine chorionic gonadotropin (e CG)-primed immature female rats. Dexamethasone (500 mug) significantly incr eased serum concentrations of FSH in hypophysectomized rats implanted with pituitary under the kidney capsule, as well as in intact rats. Serum concen trations of inhibin and estradiol in eCG (2.5, 5 i.u.)-primed rats were sig nificantly increased by simultaneous treatment with dexamethasone (500 mug) and eCG, These simultaneous effects were not confirmed in hypophysectomize d rats. The results had shown that hypophysiotropic factors do not mediate the selective increase of FSH secretion caused by dexamethasone. Dexamethas one induces the excess amount of FSH secretion from anterior pituitary and this FSH can stimulate inhibin and estradiol secretion in eCG-primed immatu re female rat. (C) 2001 Elsevier Science Inc. All rights reserved.