Restoration of Proestrous and Estrous Release of Gonadotropins in Ovariectomized Hamsters: A Possible Role for Inhibin in the Female

Changes in serum concentrations of estradiol (E2) and progesterone (P) similar to those ob-served in intact female hamsters during proestrus and estrus were restored in ovariectomized hamsters by Silastic capsule implants. E2 alone or E2 in combination with P elicited a surge release of luteinizing hormone (LH) I day after the introduction of the E2 stimulus. Neither steroid treatment regimen, however, caused the biphasic elevation in serum FSH levels normally observed in the cyclic hamster. The administration of bovine follicular fluid (a source of inhibin) on pro-estrus, either alone or in combination with gonadal steroids, elicited an elevation in serum FSH concentrations, followed by an abrupt decline and a subsequent secondary rise to control levels. These studies suggest that ovarian inhibin may play an important role in the regulation of FSH secretion during the periovulatory period in the female golden hamster.