Effects of bovine follicular fluid on pulsatile secretion of gonadotrophin-releasing hormone and gonadotrophins in ovariectomized ewes.

Abstract Ovariectomized ewes were injected with charcoal-extracted bovine follicular fluid (n = 5) or with hypophysectomized ewe serum (n = 5) after which hypophyseal portal blood samples were taken to monitor the release of gonadotrophin-releasing hormone (GnRH). Peripheral blood samples were also taken to monitor plasma luteinizing hormone and follicle-stimulating hormone (FSH) concentrations. Bovine follicular fluid treatment caused a 50% decrease in plasma FSH concentrations whereas hypophysectomized ewe serum did not significantly alter plasma FSH levels. The frequency and amplitude of luteinizing hormone and GnRH pulses was similar in both experimental groups. It is concluded that inhibin activity in bovine follicular fluid selectively suppresses the release of FSH by direct action on the pituitary gland, with no effect on GnRH secretion.