ROLE OF INHIBIN IN THE REGULATION OF FSH-SECRETION AND FOLLICULOGENESIS IN COWS

This review focuses on the role of inhibin and oestradiol in the hormo nal regulation of ovarian folliculogenesis during the oestrous cycle i n cows and other domestic animals, using data from the cow, sheep, pig , horse, rat and hamster. The evidence reviewed confirms the role of i nhibin as a chemical signal of the number of growing follicles in the ovary to the pituitary gland to reduce the secretion of follicle stimu lating hormone (FSH) to a level which maintains the species-specific n umber of ovulations. It is argued that ovarian inhibin may be the most important hormone for determining the species-specific number of ovul ations in both single and multiple ovulatory species. On the other han d, evidence presented in the review also confirms the importance of ov arian oestradiol acting as a chemical signal to indicate the maturity of growing follicles to the hypothalamo-pituitary system. This induces the preovulatory luteinising hormone (LH) surge to cause ovulation.