Hormonal regulation, localization, and functional activity of the progesterone receptor in granulosa cells of rat preovulatory follicles.
Progesterone has been implicated to play a critical role in mediating LH induction of ovulation and possibly luteinization. The present study was undertaken to determine the effects of various agonists (LH, FSH, forskolin, and GnRH) known to stimulate ovulation on their abilities to induce progesterone receptor (PR) mRNA and protein in rat preovulatory follicles and in cultured rat granulosa cells exhibiting a preovulatory phenotype. In cultured granulosa cells, PR mRNA was induced by LH in a dose- and time-dependent manner. Transcripts of approximately 11.0, 7.2, 6.8, 6.2, 3.4, and 3.1 kilobases in size were induced by ovulatory (500 ng/ml), but not low (50 ng/ml), concentrations of LH and FSH as well as by forskolin (10 microM), GnRH (1 microM), and phorbol 12-myristate 13-acetate (200 nM). Two forms (A and B) of PR protein were also induced in an agonist- and time-dependent manner, with the shorter form A (mol wt, 83,000-85,000) appearing in greater abundance than the longer form B (mol wt, 115,000). Indirect immunofluorescent analyses verified nuclear localization of the induced receptor. Forskolin and progesterone, but not progesterone alone, were able to activate a glucocorticoid (progesterone) response element-E1b-chloramphenicol acetyltransferase reporter construct (12-fold) after transfection into cultured granulosa cells. The antiprogestins RU486 and ZK98299 did not inhibit induction of PR mRNA and protein, but effectively blocked agonist activation of glucocorticoid response element2-E1b-chloramphenicol acetyltransferase, as well as LH stimulation of luteinization in vitro. These results provide direct evidence that agonists stimulating diverse intracellular pathways can induce PR in granulosa cells, that progesterone plays a functional role in the luteinization process triggered by the LH surge, and that the effects are mediated at least in part by induction of PR.
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Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030.
Richards
J S
JS
D000818:Animals; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D003338:Corpus Luteum / Q000187:drug effects / Q000502:physiology; D005260:Female; D005455:Fluorescent Antibody Technique; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D006107:Granulosa Cells / Q000187:drug effects / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000494:pharmacology; D008970:Molecular Weight; D006080:Ovarian Follicle / Q000187:drug effects / Q000502:physiology*; D010060:Ovulation; D011374:Progesterone / Q000037:antagonists & inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D011980:Receptors, Progesterone / Q000235:genetics / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection
D012333:RNA, Messenger; D011980:Receptors, Progesterone; D005576:Colforsin; D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D013755:Tetradecanoylphorbol Acetate