Tumor-promoting phorbol ester acts synergistically with insulin to induce lutropin receptor expression in rat granulosa cells.
Lutropin (LH) receptors in rat granulosa cells are expressed by activation of cAMP-dependent protein kinase in response to follitropin (FSH). In the present study, 12-O-tetradecanoylphorbol 13-acetate (TPA) could cause a dose-dependent expression of LH receptors in the presence of insulin, but not in the absence of insulin, as measured by binding of 125I-deglycosylated human choriogonadotropin (DGhCG). The synergistic action of TPA with insulin was achieved at 1 nM and 10 mIU/ml, respectively. The receptor expression induced by this synergistic action was accompanied by cAMP accumulation which was detected after a lag time of 6 h following exposure to TPA. However, a synthetic diacylglycerol and non-protein kinase C activating phorbol derivatives did not mimic the effect of TPA on the receptor expression. In addition, insulin modulated the inhibitory effect of TPA in FSH-induced LH receptor expression, indicating a peculiar action of insulin in the receptor expression. Indomethacin treatment led to a dose-dependent inhibition in the receptor expression in the cells treated with TPA plus insulin more than that in the cells with FSH plus insulin, suggesting that the synergistic action was dependent upon cyclooxygenase and/or phospholipase A2 activity. It was shown by Scatchard analysis of LH receptors and kinetic studies of hCG-stimulated cAMP formation that the synergistic action of TPA with insulin led to expression of functional LH receptors coupled with the adenylate cyclase system in cultured granulosa cells.
Hattori
M
M
Department of Pharmaceutical Chemistry, Gunma University, Maebashi, Japan.
Takahashi
M
M
Horiuchi
R
R
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D005786:Gene Expression Regulation; D006107:Granulosa Cells / Q000187:drug effects / Q000378:metabolism*; D007213:Indomethacin / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011974:Receptors, LH / Q000187:drug effects / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000031:analogs & derivatives / Q000494:pharmacology*
D006063:Chorionic Gonadotropin; D007328:Insulin; D011974:Receptors, LH; D005640:Follicle Stimulating Hormone; D000242:Cyclic AMP; D011451:Prostaglandin-Endoperoxide Synthases; D010741:Phospholipases A; D054467:Phospholipases A2; D000262:Adenylyl Cyclases; D013755:Tetradecanoylphorbol Acetate; D007213:Indomethacin