title: Differences in LH receptor down-regulation between rat and mouse Leydig cells: effects of 3',5'-cyclic AMP and phorbol esters.
abstract: The role of cyclic AMP and phorbol esters in luteinizing hormone (LH) receptor down-regulation in Leydig cells has been studied. Dibutyryl cyclic AMP (db-cAMP) (0.01, 0.1 and 1 mM), forskolin (80 microM) and cholera toxin (1.19 nM) caused a 30-50% loss of [125I]hCG binding sites and an inhibition of receptor-[125I]hCG complex internalization in mouse tumour Leydig (MA10, MLTC-1) cells during 2 h. In contrast, db-cAMP had no effect on the level of binding sites or internalization of the hormone receptor complex in rat testis Leydig cells or a rat tumour (R2C) Leydig cell. Phorbol 12-myristate 13-acetate (PMA) at concentrations from 10(-9) to 10(-5) M had no effect on hormone binding or hormone-receptor complex internalization in any of the Leydig cells. In contrast a 2 h preincubation of MLTC-1 cells with 10(-7) M PMA caused a loss of subsequent LH-stimulated cyclic AMP and pregnenolone production. These results indicate that LH receptor down-regulation is mediated by cyclic AMP dependent kinase, but not protein kinase C, in mouse Leydig cells. No down-regulation of rat Leydig cell LH receptor occurs with either kinase.
authors.affiliation: Department of Biochemistry, Royal Free Hospital School of Medicine, London, U.K.
authors.forename: A P
authors.initials: AP
authors.lastname: West
authors.forename: M P
authors.initials: MP
authors.lastname: Lopez-Ruiz
authors.forename: B A
authors.initials: BA
authors.lastname: Cooke
mesh_terms: D000818:Animals; D001665:Binding Sites; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D015536:Down-Regulation; D007985:Leydig Cells / Q000378:metabolism*; D008297:Male; D051379:Mice; D011480:Protease Inhibitors / Q000494:pharmacology; D051381:Rats; D011974:Receptors, LH / Q000378:metabolism*; D012756:Sheep; D013045:Species Specificity; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
chemical_list: D011480:Protease Inhibitors; D011974:Receptors, LH; D000242:Cyclic AMP; D013755:Tetradecanoylphorbol Acetate