title: Dopamine D(2) receptor expression and regulation of gonadotropin alpha-subunit gene in clonal gonadotroph LbetaT2 cells.
abstract: This study investigated the role of dopamine on the regulation of gonadotropin secretion at the gonadotroph cell line. We examined the function of the dopamine D(2) receptor in the regulation of pituitary gonadotropin gene expression using LbetaT2 cells, a mature, well differentiated clonal gonadotroph cell line. The presence of the dopamine D(2) receptor in the LbetaT2 cells was confirmed by both RT-PCR and Western blot. Gonadotropin releasing hormone (GnRH) stimulation resulted in gonadotropin LHbeta, FSHbeta and alpha-subunit promoter activation, and none were inhibited by quinpirol, a specific dopamine D(2) receptor agonist. Pituitary adenylate cyclase-activating polypeptide (PACAP) increased gonadotropin alpha-subunit promoter activity, but not LHbeta and FSHbeta promoter activity. The activity of PACAP was significantly inhibited in the presence of quinpirol. The protein kinase A inhibitor, H89, also inhibited PACAP-induced alpha-subunit gene expression. PACAP increased intracellular cAMP more than GnRH did in LbetaT2 cells, and the elevation of cAMP was strongly inhibited in the presence of various dopamine D(2) agonists. These results suggest that in pituitary gonadotrophs, the dopamine D(2) receptor is a negative regulator of gonadotropin alpha-subunit gene expression which is induced by cAMP-elevating factors in a cAMP-dependent pathway.
authors.affiliation: Department of Obstetrics and Gynecology, Shimane University, School of Medicine, Enya Cho 89-1, Izumo 693-8501, Shimane Prefecture, Japan.
authors.forename: Sandra
authors.initials: S
authors.lastname: Mutiara
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Kanasaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Harada
authors.forename: Kohji
authors.initials: K
authors.lastname: Miyazaki
mesh_terms: D000818:Animals; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D005786:Gene Expression Regulation; D015292:Glycoprotein Hormones, alpha Subunit / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000378:metabolism; D019257:Quinpirole / Q000494:pharmacology; D051381:Rats; D017448:Receptors, Dopamine D2 / Q000819:agonists / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology; D015533:Transcriptional Activation / Q000187:drug effects
chemical_list: D015292:Glycoprotein Hormones, alpha Subunit; D047908:Intracellular Signaling Peptides and Proteins; D007546:Isoquinolines; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D020033:Protein Isoforms; D017448:Receptors, Dopamine D2; D013449:Sulfonamides; C015482:protein kinase modulator; D019257:Quinpirole; D007987:Gonadotropin-Releasing Hormone; D000242:Cyclic AMP; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide