An increase of pituitary 3', 5' cyclic adenosine monophosphate produced by estradiol benzoate in vitro: possible implication of this increase in the secretion of luteinizing hormone.

In an attempt to study the site and mechanism of action of estrogen in producing positive feedback control, porcine anterior pituitary slices were incubated in vitro in the presence of estradiol benzoate (EB). EB elevated pituitary cyclic AMP concentration within 5 min and augmented pituitary release of luteinizing hormone (LH). The magnitude of increase of cyclic AMP and LH release was related to the doses of EB used. Also, luteinizing hormone releasing hormone (LH-RH) elevated pituitary cyclic AMP concentration and stimulated pituitary release of LH. The magnitude of increase of cyclic AMP and LH release was inversely related to the doses of LH-RH used. EB and LH-RH were additive in increasing cyclic AMP. Progesterone and clomiphene citrate interfered with an increase of pituitary cyclic AMP produced by EB, but did not significantly affect the basal level of pituitary cyclic AMP. Testosterone propionate, human chorionic gonadotropin and hexestrol were without effect on either basal or stimulated level of pituitary cyclic AMP. Since cyclic AMP and dibutyryl cyclic AMP (DBC) stimulated LH release, it is suggested that EB directly stimulates the release of LH by augmenting cyclic AMP synthesis in the anterior pituitary.