STEROIDOGENESIS IN SHEEP OVARIAN ANTRAL FOLLICLES IN CULTURE - TIME-COURSE STUDY AND SUPPLEMENTATION WITH A PRECURSOR

The present study was designed to explore the steroidogenic responsive ness of ovine antral follicles of different sizes when cultured for va rying time-periods with different doses of pregnenolone. Antral follic les of different sizes were isolated from sheep ovaries and cultured i n medium 199 with or without pregnenolone in the presence or absence o f FSH for 1, 6, 10, and 24 hours at 37 C. The levels of progesterone a nd estradiol in the spent medium were estimated. In the absence of pre gnenolone, steroid production by the follicles did not increase signif icantly beyond 1 hour of culture. However, in the presence of pregneno lone there was a significant increase in progesterone production at 6, 10, and 24 hours of culture compared to controls. Estradiol levels we re unaffected. Addition of FSH in combination with pregnenolone failed to increase progesterone or estradiol levels beyond that seen with pr egnenolone alone. These data demonstrate that short-term incubation of follicles is sufficient for the secretion of steroids into the cultur e medium and supplementation of the culture medium with an immediate p recursor is essential for optimal steroidogenesis in vitro.