title: Loss of basal and TRH-stimulated Tshb expression in dispersed pituitary cells.
abstract: This study addresses the in vivo and in vitro expression pattern of three genes that are operative in the thyrotroph subpopulation of anterior pituitary cells: glycoprotein α-chain (Cga), thyroid-stimulating hormone β-chain (Tshb), and TRH receptor (Trhr). In vivo, the expression of Cga and Tshb was robust, whereas the expression of Trhr was low. In cultured pituitary cells, there was a progressive decline in the expression of Cga, Tshb, and Trhr. The expression of Tshb could not be reversed via pulsatile or continuous TRH application in variable concentrations and treatment duration or by the removal of thyroid and steroid hormones from the sera. In parallel, the expression of CGA and TSHB proteins declined progressively in pituitary cells from both sexes. The lack of the effect of TRH on Tshb expression was not related to the age of pituitary cultures and the presence of functional TRH receptors. In cultured pituitary fragments, there was also a rapid decline in expression of these genes, but TRH was able to induce transient Tshb expression. In vivo, thyrotrophs were often in close proximity to each other and to somatotroph and folliculostellate cell networks and especially to the lactotroph cell network; such an organization pattern was lost in vitro. These observations suggest that the lack of influence of anterior pituitary architecture and/or intrapituitary factors probably accounts for the loss of basal and TRH-stimulated Tshb expression in dispersed pituitary cells.
authors.affiliation: Section on Cellular Signaling (P.B.-S., M.K., I.B., M.T., M.M.J., S.S.S.), The Eunice Kennedy Shiver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-4510; and Department of Physiology and Biophysics (P.B.-S., M.T.N.), Institute of Biomedical Sciences, University of São Paulo, 05508-000 São Paulo, SP, Brazil.
authors.forename: Paula
authors.initials: P
authors.lastname: Bargi-Souza
authors.forename: Marek
authors.initials: M
authors.lastname: Kucka
authors.forename: Ivana
authors.initials: I
authors.lastname: Bjelobaba
authors.forename: Melanija
authors.initials: M
authors.lastname: Tomić
authors.forename: Marija M
authors.initials: MM
authors.lastname: Janjic
authors.forename: Maria Tereza
authors.initials: MT
authors.lastname: Nunes
authors.forename: Stanko S
authors.initials: SS
authors.lastname: Stojilkovic
mesh_terms: D000375:Aging; D000818:Animals; D002478:Cells, Cultured; D005260:Female; D005786:Gene Expression Regulation; D015292:Glycoprotein Hormones, alpha Subunit / Q000235:genetics / Q000378:metabolism; D008297:Male; D010903:Pituitary Gland, Anterior / Q000166:cytology*; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012741:Sexual Maturation; D013972:Thyrotropin / Q000235:genetics / Q000378:metabolism*; D037322:Thyrotropin, beta Subunit / Q000235:genetics / Q000378:metabolism*
chemical_list: D015292:Glycoprotein Hormones, alpha Subunit; D021122:Protein Subunits; D037322:Thyrotropin, beta Subunit; D013972:Thyrotropin