Effects of phorbol esters on steroidogenesis in small bovine luteal cells.
The possible influence of an activator of protein kinase C, the tumor-promoting phorbol ester, PMA (phorbol-12-myristate-13-acetate), upon small bovine luteal cell steroidogenesis was investigated in vitro, PMA had no significant effect on basal and dibutyryl cyclic AMP (dbcAMP)-stimulated progesterone production but markedly modulated the LH-stimulated progesterone and cAMP productions. PMA potentiated the LH-stimulated cAMP accumulation whatever the dose of LH used. It also potentiated the LH-induced progesterone production in the presence of low doses of LH. Paradoxically, in the presence of maximal or submaximal effective doses of LH, PMA exerted a time- and dose-dependent inhibition of progesterone synthesis. Diacylglycerol was able to mimic the effects of PMA on LH-induced steroidogenesis. These observations suggest that the Ca2+- and phospholipid-dependent protein kinase C can modulate the regulation by LH of small bovine luteal cell steroidogenesis at a step before the synthesis of cAMP. They also suggest that the interaction between LH and its receptor is able to trigger a negative regulatory signal which would be only expressed for high doses of LH and in the presence of an activator of PKC.
Benhaim
A
A
Laboratoire de Biochimie, CNRS-UA 609-GS 79, Faculté de Médecine, Caen, France.
Herrou
M
M
Mittre
H
H
Leymarie
P
P
D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D003338:Corpus Luteum / Q000378:metabolism*; D000242:Cyclic AMP / Q000096:biosynthesis; D004075:Diglycerides / Q000494:pharmacology; D005260:Female; D007986:Luteinizing Hormone / Q000494:pharmacology; D011374:Progesterone / Q000096:biosynthesis*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D004075:Diglycerides; D011374:Progesterone; D007986:Luteinizing Hormone; D000242:Cyclic AMP; D013755:Tetradecanoylphorbol Acetate