title: Hormonal activation of phospholipid methyltransferase in the Leydig cell.
abstract: Hormonal stimulation of purified rat Leydig cells with hCG caused a 2-fold increase in phospholipid methyltransferase activity within 10 min. This effect of gonadotropin was concentration dependent, with maximal activation of methyltransferase at 10(-12) M hCG, and was reproduced by 8-bromo-cAMP. Hormonal activation of phospholipid methyltransferase caused an increase in the maximum velocity of the enzyme, without changing the Km for S-adenosylmethionine. Analysis of the pattern of radiolabeled phospholipids from Leydig cells showed that the incorporation of methyl groups and the increase in phospholipid methylation stimulated by 8-bromo-cAMP occurred mainly in phosphatidyl-N-monomethylethanolamine. The rapid and highly sensitive increase in phospholipid methylation in hCG-stimulated Leydig cells is consistent with a role of methyltransferase in the hormonal activation mechanism probably at a step subsequent to cAMP production.
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000818:Animals; D002772:Cholera Toxin / Q000494:pharmacology; D006063:Chorionic Gonadotropin / Q000494:pharmacology*; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004789:Enzyme Activation; D066298:In Vitro Techniques; D007700:Kinetics; D007985:Leydig Cells / Q000201:enzymology*; D008297:Male; D008780:Methyltransferases / Q000378:metabolism*; D050941:Phosphatidyl-N-Methylethanolamine N-Methyltransferase; D050918:Phosphatidylethanolamine N-Methyltransferase; D051381:Rats
chemical_list: D006063:Chorionic Gonadotropin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D002772:Cholera Toxin; D000242:Cyclic AMP; D008780:Methyltransferases; D050918:Phosphatidylethanolamine N-Methyltransferase; D050941:Phosphatidyl-N-Methylethanolamine N-Methyltransferase; D015056:1-Methyl-3-isobutylxanthine