Progesterone modulation of gonadotropin secretion by dispersed rat pituitary cells in culture. III. A23187, cAMP, phorbol ester and DiC8-stimulated luteinizing hormone release.
Dispersed estradiol-treated rat pituitary cells were used to characterize progesterone (P) modulation of luteinizing hormone (LH) secretion in response to a variety of pharmacologic secretagogues which influence cell biochemistry. Acute (less than 3 h) and chronic (24 h) exposures to P prior to secretagogue challenge respectively enhanced and inhibited Ca2+ ionophore (A23187)-stimulated and gonadotropin-releasing hormone (GnRH)-stimulated LH release in similar quantitative fashion without any effect on concurrent prolactin release. Similar responses were also noted with cholera toxin-stimulated secretion. However, when protein kinase C activators such as phorbol esters and dioctanoylglycerol were used to trigger LH release, chronic exposure to P did not inhibit, but rather enhanced, LH release. Again, P had no effect on prolactin release. 'Washout' studies indicated that chronic treatments with P would suppress LH secretion stimulated by these compounds, but only when the steroid was cleared from the cells 4 h beforehand. These studies provide further evidence that P specifically modulates gonadotroph secretory function via mechanisms which bypass GnRH receptors. Moreover, they suggest that P exerts many different actions within the gonadotroph and question the role of protein kinase C in GnRH action.
Krey
L C
LC
Laboratory of Neuroendocrinology, Rockefeller University, New York, NY 10021.
Kamel
F
F
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002478:Cells, Cultured; D002772:Cholera Toxin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology; D004075:Diglycerides / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D007986:Luteinizing Hormone / Q000378:metabolism*; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism*; D010906:Pituitary Hormone-Releasing Hormones / Q000494:pharmacology; D011374:Progesterone / Q000494:pharmacology*; D011388:Prolactin / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D004075:Diglycerides; D010906:Pituitary Hormone-Releasing Hormones; C044295:1,2-dioctanoylglycerol; D000001:Calcimycin; D011374:Progesterone; D004958:Estradiol; D011388:Prolactin; D007986:Luteinizing Hormone; D002772:Cholera Toxin; D000242:Cyclic AMP; D013755:Tetradecanoylphorbol Acetate