title: Beta1-adrenoceptor expression in rat anterior pituitary gonadotrophs and in mouse alphaT3-1 and LbetaT2 gonadotrophic cell lines.
abstract: The rat anterior pituitary expresses beta(2)-adrenoceptors (ARs) on somatotrophs, lactotrophs, and corticotrophs. The present study investigates whether beta(1)-ARs exist in the anterior pituitary, in which cell type(s) they are found, and whether they are regulated by glucocorticoids. As determined by quantitative RT-PCR and Western immunoblotting, the rat anterior pituitary expressed beta(1)-AR mRNA and protein. Unlike the beta(2)-AR, expression decreased to very low levels after 5-d aggregate cell culture but was strongly up-regulated in a dose- and time-dependent manner by dexamethasone (DEX). Glucocorticoids attenuated isoproterenol-induced down-regulation of beta(1)-AR mRNA levels. As examined by immunofluorescence confocal microscopy, beta(1)-AR immunoreactivity was detected in a subpopulation of gonadotrophs, but not in somatotrophs, lactotrophs, corticotrophs, thyrotrophs, or folliculo-stellate cells. beta(1)-AR-immunoreactivity cells were often surrounded by cup-shaped lactotrophs. Consistent with these findings, beta(1)-AR mRNA was considerably more abundant in the gonadotrophic alphaT3-1 and LbetaT2 cell lines than in the GHFT, GH3, and TtT/GF cell lines. DEX did not affect expression level in the cell lines. DEX also failed to up-regulate beta(1)-AR mRNA levels in aggregates from a subpopulation enriched in large gonadotrophs obtained by gradient sedimentation. In contrast, excessive DEX-dependent up-regulation of beta(1)-AR mRNA was found in a subpopulation enriched in small nonhormonal cells. The present data indicate that beta(1)-AR is expressed in a subpopulation of gonadotrophs with a topographical relationship to lactotrophs. However, the glucocorticoid-induced up-regulation does not seem to occur directly in the gonadotrophs but within (an)other unidentified cell type(s), or is transduced by that cell type on gonadotrophs.
authors.affiliation: Laboratory of Cell Pharmacology, University of Leuven, Medical School, Gasthuisberg, B-3000 Leuven, Belgium.
authors.forename: Kristel
authors.initials: K
authors.lastname: Janssens
authors.forename: Olga
authors.initials: O
authors.lastname: Krylyshkina
authors.forename: Nicole
authors.initials: N
authors.lastname: Hersmus
authors.forename: Hugo
authors.initials: H
authors.lastname: Vankelecom
authors.forename: Carl
authors.initials: C
authors.lastname: Denef
mesh_terms: D058665:Adrenergic beta-1 Receptor Agonists; D058666:Adrenergic beta-2 Receptor Agonists; D000818:Animals; D002460:Cell Line; D003907:Dexamethasone / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D005938:Glucocorticoids / Q000494:pharmacology; D015292:Glycoprotein Hormones, alpha Subunit / Q000378:metabolism; D052681:Gonadotrophs / Q000187:drug effects / Q000378:metabolism*; D007545:Isoproterenol / Q000494:pharmacology; D037101:Luteinizing Hormone, beta Subunit / Q000378:metabolism; D008297:Male; D051379:Mice; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism; D052716:Pituitary Gland, Intermediate / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018342:Receptors, Adrenergic, beta-1 / Q000235:genetics* / Q000378:metabolism; D018343:Receptors, Adrenergic, beta-2 / Q000235:genetics / Q000378:metabolism
chemical_list: D058665:Adrenergic beta-1 Receptor Agonists; D058666:Adrenergic beta-2 Receptor Agonists; D005938:Glucocorticoids; D015292:Glycoprotein Hormones, alpha Subunit; D037101:Luteinizing Hormone, beta Subunit; D012333:RNA, Messenger; D018342:Receptors, Adrenergic, beta-1; D018343:Receptors, Adrenergic, beta-2; D003907:Dexamethasone; D007545:Isoproterenol