Role of the extra-follicular compartment in the ovulation of isolated rabbit ovarian follicles

Summary.Ovulation was never observed, even in the presence of gonadotrophins, when preovulatory follicles isolated from oestrous does were cultured in vitro(n= 112). If the follicles were co-cultured with pieces of ovarian tissue and gonadotrophins, then 50% ovulated (P< 0·01). Attempts to replace the ovarian tissue by various steroid hormones or prostaglandins did not result in follicular rupture except when PGE-2 was used (23·8%, P< 0·05). We suggest that gonadotrophins have an immediate (<1 h) action upon the follicle and ovarian interstitial tissue simultaneously. The response of the ovarian tissue to gonadotrophins is essential for eventual follicular rupture and involves PGE-2.