title: Thyroid hormones regulate pituitary growth hormone secretagogue receptor gene expression.
abstract: Thyroid hormones regulate growth hormone (GH) secretion by actions both at the hypothalamus and at the pituitary gland. At the level of the pituitary, thyroid hormones increase GH and GH-releasing hormone receptor (GHRH-R) mRNA expression. To test if thyroid hormones might also regulate the pituitary expression of mRNA for the recently identified GH secretagogue (GHS) receptor, GHS-R, primary pituitary cell cultures from adult male rats were treated with triiodothyronine (T3) and GHS-R mRNA levels were assessed by reverse transcriptase-polymerase chain reaction. T3 increased pituitary GHS-R mRNA levels in a dose- and time-dependent manner. The stimulatory action of T3 on GHS-R mRNA levels was also observed in the presence of the RNA synthesis inhibitor, actinomycin D, indicating that gene transcription is not required. Closer examination of the decay rates of GHS-R mRNA in the presence of actinomycin D revealed T3 extended the half-life of the GHS-R mRNA from 8 h (basal) to15 h, demonstrating that T3 increases GHS-R mRNA levels in vitro by increasing message stability.
authors.affiliation: Department of Medicine, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603, Japan. jkamegai@nms.ac.jp
authors.forename: J
authors.initials: J
authors.lastname: Kamegai
authors.forename: H
authors.initials: H
authors.lastname: Tamura
authors.forename: S
authors.initials: S
authors.lastname: Ishii
authors.forename: H
authors.initials: H
authors.lastname: Sugihara
authors.forename: I
authors.initials: I
authors.lastname: Wakabayashi
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003609:Dactinomycin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects*; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000235:genetics; D006207:Half-Life; D007700:Kinetics; D008297:Male; D010902:Pituitary Gland / Q000737:chemistry*; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011956:Receptors, Cell Surface / Q000235:genetics*; D043562:Receptors, G-Protein-Coupled; D054440:Receptors, Ghrelin; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014284:Triiodothyronine / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D054440:Receptors, Ghrelin; D014284:Triiodothyronine; D003609:Dactinomycin; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases