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KMID : 0578319940040040473
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Molecules and Cells
1994 Volume.4 No. 4 p.473 ~ p.479
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A Local Regulation of GnRH Release and Gene Expression in Rat Granulosa Cells by Endoenous Opioid Peptide and GnRH Analogues
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Lee, sung Ho
choi, Wan sung/Kim, Changmee/Kang, hae Mook/Geum, Dongho/park, Hye-Seong/Park, Young Mok
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Abstract
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The present study examines whether gene expression and secretion of gonadotropin releasing hormone (GnRH) from rat granulosa cells are locally regulated by endogenous opioid peptide (EOP) and GnRH analogues, and explores possible intracellular signal transduction pathways involved in GnRH release and gene expression. Rat granulosa cells were isolated from immature rat ovaries and incubated with testing agents. GnRH release and cAMP levels in media were determined by respective radioimmunoassays, and GnRH mRNA levels were determined by RNA-blot hybridization. Treatment of granulosa cells with Q-endorphin decreased GnRH release, cAMP accumulation, and GnRH mRNA levels in a dose-dependent manner. These inhibitory effects were reversed by naloxone, a p-type opioid receptor antagonist. Other EOPs, leu- and met-enkephalins, also resulted in a decrease of GnRH mRNA levels. Activation of adenylate cyclase with forskolin increased GnRH mRNA levels in parallel with changes in GnRH release in a dose-dependent manner. Forskolin-stimulated GnRH mRNA levels were blocked by either econazole or miconazole, both of which are well known adenylate cyclase inactivators. TPA (12-o-tetradecanoyl phorbol-13-acetate), a potent protein kinase C activator, also increased GnRH mRNA levels and GnRH release in a dose-dependent manner. GnRH agonist increased GnRH mRNA levels, whereas GnRH antagonist decreased GnRH mRNA levels. In addition, GnRH receptor mRNA was present in the rat ovary. Taken together, the present study suggests that there exists an intraovarian autocrine and/or paracrine loop composed of two local media-tors, GnRH and EOP, for controlling granulosa cell functions.
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