1. Regulation of gonadotropin alpha subunit gene expression by dopamine D(2) receptor agonist in clonal mouse gonadotroph alphaT3-1 cells.
- Author
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Kanasaki H, Yonehara T, Yamada Y, Takahashi K, Hata K, Fujiwaki R, Yamamoto H, Takeuchi Y, Fukunaga K, Miyamoto E, and Miyazaki K
- Subjects
- Animals, Blotting, Western, Cell Line, Cyclic AMP metabolism, Enzyme Activation drug effects, Enzyme Inhibitors pharmacology, Flavonoids pharmacology, Gonadotropin-Releasing Hormone pharmacology, Mice, Mitogen-Activated Protein Kinases antagonists & inhibitors, Mitogen-Activated Protein Kinases metabolism, Neuropeptides pharmacology, Pituitary Adenylate Cyclase-Activating Polypeptide, Pituitary Gland chemistry, Quinpirole pharmacology, RNA, Messenger analysis, Receptors, Dopamine D2 genetics, Receptors, Dopamine D2 physiology, Reverse Transcriptase Polymerase Chain Reaction, Gene Expression Regulation drug effects, Glycoprotein Hormones, alpha Subunit genetics, Pituitary Gland metabolism, Receptors, Dopamine D2 agonists
- Abstract
Pituitary prolactin biosynthesis is negatively regulated by hypothalamic dopamine through D(2) receptors in pituitary lactotrophs, but little is known about the direct effect of dopamine on gonadotrophs. In this study, the clonal gonadotroph-derived cell line, alphaT3-1, was used to examine whether gene expression of the pituitary gonadotropin alpha subunit, stimulated with GnRH or pituitary adenylate cyclase-activating polypeptide (PACAP), was controlled by dopamine D(2) receptor. Western blotting and reverse transcription-polymerase chain reaction analysis demonstrated the presence of dopamine D(2) receptors in alphaT3-1 cells. Both GnRH and PACAP increased alpha subunit gene expression. GnRH-induced alpha subunit gene expression was not affected by quinpirol, a specific dopamine D(2) receptor agonist. In contrast, PACAP-induced gene expression was significantly lower in the presence of quinpirol. The roles of extracellular signal-regulated kinase (ERK) and cAMP in the expression of the alpha subunit gene were examined. GnRH activated ERK, but PACAP did not, and the activation was not inhibited by quinpirol. GnRH-induced alpha subunit gene expression was completely inhibited by an ERK inhibitor, PD098059. Cyclic AMP accumulation in alphaT3-1 cells was increased by treatment with PACAP, and quinpirol inhibited this effect. GnRH did not affect cAMP production in these cells. These results suggest that in alphaT3-1 cells, dopamine D(2) receptors negatively regulate pituitary alpha subunit gene expression in association with the cAMP-dependent pathway, but not with the ERK pathway.
- Published
- 2002
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