title: Retinoic acid and dexamethasone induce differentiation and maturation of somatotroph cells at different stages in vitro.
abstract: The purpose of this study was to investigate the role of retinoic acid (RA) and/or dexamethasone and growth hormone releasing hormone (GHRH) in the induction of somatotroph cell differentiation. Immunohistochemistry, radioimmunoassay, 3-(4,5-dimethylthiazol -1,2-y1)-2,5-diphenyltetrazolium bromide assay, and immune electron microscopy were employed to determine the effect of incubation with these constituents on the differentiation into somatotrophs of cells isolated from the rat embryonic pituitary gland. RA administration increased the proportion of growth hormone (GH) positive somatotroph cells and GH secretion in embryonic pituitary cells (P<0.01). After 4 days of incubation with RA, additional administration of dexamethasone further increased the proportion of somatotroph cells and GH secretion (P<0.01), and increased the number of secretory granules in the somatotroph cells. Addition of GHRH alone had no such effect (P>0.05). However, addition of GHRH to treatment with RA plus dexamethasone significantly increased both the proportion of somatotroph cells and the secretion of GH compared to treatment with RA or dexamethasone alone or RA plus dexamethasone (P<0.01). RA promoted the early differentiation of somatotroph cells, dexamethasone promoted the differentiation and maturation of somatotroph cells and in addition, RA, dexamethasone and GHRH together exerted synergistic effects that markedly promoted somatotroph cell differentiation, maturation and GH secretion.
authors.affiliation: The Department of Neurological Surgery, First Affiliated Hospital, Harbin Medical University, Harbin, P.R.China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Cheng
authors.forename: Ying
authors.initials: Y
authors.lastname: Xiang
authors.forename: Youzhi
authors.initials: Y
authors.lastname: Lin
authors.forename: Songbin
authors.initials: S
authors.lastname: Fu
authors.forename: Wenzhi
authors.initials: W
authors.lastname: Jia
authors.forename: Guanghui
authors.initials: G
authors.lastname: Zhang
authors.forename: Wenming
authors.initials: W
authors.lastname: Lv
authors.forename: Shan
authors.initials: S
authors.lastname: Mi
authors.forename: Qinghai
authors.initials: Q
authors.lastname: Zhao
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology*; D005260:Female; D013006:Growth Hormone / Q000378:metabolism; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology; D008297:Male; D023421:Models, Animal; D010902:Pituitary Gland / Q000166:cytology / Q000196:embryology; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D052683:Somatotrophs / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D013997:Time Factors; D014212:Tretinoin / Q000494:pharmacology*
chemical_list: D014212:Tretinoin; D003907:Dexamethasone; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone