title: Demonstration of an antiglucocorticoid action of progesterone on the corticosterone inhibition of beta-endorphin release by rat anterior pituitary in primary culture.
abstract: The effects of progesterone or 17 alpha-hydroxyprogesterone on corticosterone regulation of beta-endorphin (beta-end) release have been studied in vitro using primary culture of rat anterior pituitaries. Incubation of pituitary cells with ovine corticotropin-releasing factor (CRF) for 2 h resulted in a dose-dependent increase in beta-end release. Maximal stimulation was obtained with 200 ng/ml CRF. Preincubation for 2 h with corticosterone resulted in a dose-dependent inhibition of CRF-induced beta-end release. When the cultures were preincubated for 2 h with 200 ng/ml corticosterone and increasing concentrations (1, 10, 100, 1,000, and 10,000 ng/ml) of progesterone, a significant decrease in the corticosterone feedback action was observed with 100 ng/ml progesterone. Complete inhibition of the action of 200 ng/ml corticosterone was achieved with 10,000 ng/ml progesterone. Moreover, when the cultures were preincubated with increasing concentrations of corticosterone in the presence of 100 ng/ml progesterone, the ED50 of corticosterone increased significantly from 212 +/- 36 to 940 +/- 42 ng/ml (mean +/- SEM; P less than 0.01). Under the same conditions, 17 alpha-hydroxyprogesterone had no effect. These data demonstrate that progesterone antagonizes the corticosterone feedback inhibition of beta-end release by rat anterior pituitary.
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003345:Corticosterone / Q000494:pharmacology*; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004723:Endorphins / Q000378:metabolism*; D005260:Female; D006908:Hydroxyprogesterones / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D011374:Progesterone / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors; D001615:beta-Endorphin
chemical_list: D004723:Endorphins; D006908:Hydroxyprogesterones; D011374:Progesterone; D001615:beta-Endorphin; D003346:Corticotropin-Releasing Hormone; D003345:Corticosterone