In-vitro ovulation of rabbit ovarian follicles isolated after the endogenous gonadotrophin surge.

Follicular rupture was never observed when preovulatory rabbit follicles were isolated from the ovary before the ovulatory gonadotrophin discharge and placed in hormone-free culture for 10-14 h (n = 48). However, if the follicles were taken 1 h post coitum and cultured under the same conditions, 11/24 (45.8%) ruptured spontaneously. Follicular rupture under these conditions appeared to be chronologically and histologically comparable to that of ovulation in vivo. Culture in the presence of progesterone increased the proportion of follicles ovulating in vitro (17/23 = 73.9%; P less than 0.05). Inhibition in vitro of the synthesis of steroids or prostaglandins suppressed ovulation, although meiotic maturation of the oocyte did take place. These findings indicate that the follicle constitutes an independent entity within the ovary from 1 h post coitum.