Homologous and heterologous ligands downregulate follicle-stimulating hormone receptor mRNA in porcine granulosa cells

We investigated homologous and heterologous downregulation of FSH receptor mRNA in porcine granulosa cells from ovaries of immature pigs. Cultures wer e treated with 0, 40, or 200 ng/ml porcine FSH or medium and terminated at 24 hr intervals for Northern analysis of FSH receptor and cytochrome P450 s ide chain cleavage (P450scc) mRNA, and for radioimmunoassay of progesterone . Cells luteinized over 96 hr, and control cultures displayed increases in P450scc (8-10 fold) and FSH receptor (2 fold) mRNA and progesterone (100 fo ld). FSH reduced FSH receptor mRNA by 50-90%, increased P450scc mRNA 8 fold within 48 hr, and elevated progesterone logarithmically over 96 hr. Lutein ized cells, (after 96 hr) received FSH or LH (1-200 ng/ml) or prostaglandin E-2 (0.01-1.0 mg/ml) for 6 hr resulting in increased P450scc mRNA (2-8 fol d), and progesterone (2-5 fold), and reduced FSH receptor mRNA. FSH (200 ng /ml) or the cAMP analog, dbcAMP (1 mM) for 0-24 hr reduced FSH receptor mRN A to 15% of control from 4-24 hr and elevated P450scc mRNA at 4 and 6 hr, r espectively, to maxima at 12-24 hr. Forskolin (1-10 mM) increased P450scc m RNA (2-3 fold) and downregulated FSH receptor mRNA, effects reversed by the inhibitor of cAMP, rpcAMPs. Both epidermal growth factor, and the activato r of the protein kinase C pathway, phorbol 12-myristate, 13-acetate (PMA) a t 10 nM reduced FSH receptor mRNA. We conclude that downregulation of FSH r eceptor mRNA in luteinized granulosa cells is mediated by both homologous a nd heterologous ligands which employ cAMP, and that growth factors that act ivate the PKC pathway reduce FSH receptor and P450scc mRNA abundance. Mol. Reprod. Dev. 53:198-207, 1999. (C) 1999 Wiley-Liss, Inc.