Acute influence of LH and FSH on cyclic AMP formation in isolated granulosa cells of the rat.

A technique for the mechanical isolation of granulosa cells from the rat ovary is described. Cyclic AMP formation by the isolated granulosa cells of the follicles in various stages of development was studied in response to the administration in vitro of gonadotrophins. In granulosa cells from small to medium-sized follicles FSH but no LH stimulated cAMP formation, while in cells from pre-ovulatory follicles both gonadotrophins had a stimulatory effect. The effects of both gonadotrophins were transient with a maximal response after 15 to 60 min of incubation. In the presence of the phosphodiesterase inhibitor, 3-isobutyl-methylxanthine, the action of FSH was potentiated and prolonged while the response to LH was unaffected. These data indicate that both gonadotrophins activate the adenylate cyclase system of the isolated granulosa cells while FSH in addition stimulates the phosphodiesterase activity. Consecutive determinations of cAMP during and after the pre-ovulatory LH-FSH surge, demonstrated a rise of cAMP levels in granulosa cells from the pre-ovulatory follicles following endogenous gonadotrophin release. cAMP levels remained high or increased until the time of ovulation.