Effect of 17 beta-estradiol on pituitary cAMP binding and responses to DBcAMP

Effects of 17 beta-estradiol (E2) on adenosine 3',5'-cyclic monophosphate (cAMP) binding and luteinizing hormone (LH) and prolactin (PRL) responses to N6-O-2'-dibutyryl cAMP (DBcAMP) were examined in pituitary monolayer cultures prepared from female rats. Incubation with 8 mM DBcAMP for 4 h significantly (P less than 0.05) increased both LH and PRL release into medium by two- to threefold. E2 pretreatment augmented the DBcAMP-induced LH release but not PRL release to 160% of the non-E2-treated controls. However, the cellular and total accumulation of both LH and PRL were significantly increased in cultures pretreated with E2. The effect of E2 was time dependent, and the maximal effect was observed after 3 days of treatment. Furthermore, E2 treatment significantly increased cAMP-binding activities to 254% of the non-E2-treated controls. The time course of the E2 effect on cAMP-binding activities closely resembled the time course of the E2 effect on LH and PRL accumulation as well as the DBcAMP-induced LH release. These results suggest that the priming effect of E2 on pituitary LH and PRL responses to DBcAMP is associated with increased hormone synthesis and cAMP binding stimulated by E2 pretreatment.