title: Glucocorticoid-regulated expression of exogenous human growth hormone gene in rats.
abstract: The aim of this study was to control in vitro and in vivo expression of the growth hormone (GH) gene using a glucocorticoid-sensitive promoter, the mouse mammary tumor virus long terminal repeat (MMTV LTR). We inserted the cDNA encoding the 20-kDa form of human GH (20K-GH) downstream of the MMTV LTR of plasmid pMSG, and used lipofection to transfer it to 3Y1 cells together with plasmid pMX, which contains a puromycin-resistant element. The secretion of GH from the selected transformants was dose-dependently augmented by the application of hydrocortisone, corticosterone, or dexamethasone, among which dexamethasone was the most potent. Analysis of the time course showed that 20K-GH secretion began to increase within 2 hours after the addition of glucocorticoid and reached a maximal level of about threefold over the unstimulated control at 3 hours; secretion then gradually declined and returned to near basal levels at 19 hours. Repeated glucocorticoid application led to repeated increases in GH secretion. When GH-producing cells were microcapsulated and transplanted into the abdominal cavities of rats, 20K-GH was detected in the plasma under control conditions and increased about 3.3-fold after administration of dexamethasone. We suggest that GH expression driven by the MMTV LTR promoter may be under the control of an endogenous glucocorticoid in vivo.
authors.affiliation: Department of Advanced Medical Science, The Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo, 108-8639, Japan. inazawat@ims.u-tokyo.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Inazawa
authors.forename: T
authors.initials: T
authors.lastname: Tanabe
authors.forename: H
authors.initials: H
authors.lastname: Yamada
authors.forename: T
authors.initials: T
authors.lastname: Nakaoka
authors.forename: Y
authors.initials: Y
authors.lastname: Hashimoto
authors.forename: T
authors.initials: T
authors.lastname: Yamasaki
authors.forename: H
authors.initials: H
authors.lastname: Kotaki
authors.forename: K
authors.initials: K
authors.lastname: Tani
authors.forename: S
authors.initials: S
authors.lastname: Asano
authors.forename: N
authors.initials: N
authors.lastname: Yamashita
mesh_terms: D000818:Animals; D002214:Capsules; D002460:Cell Line; D017690:Cell Transplantation; D003345:Corticosterone / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects*; D015316:Genetic Therapy / Q000379:methods; D005938:Glucocorticoids / Q000494:pharmacology*; D019382:Human Growth Hormone / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D006854:Hydrocortisone / Q000494:pharmacology; D008297:Male; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D051381:Rats; D015183:Restriction Mapping; D020079:Terminal Repeat Sequences / Q000235:genetics; D013997:Time Factors; D014162:Transfection
chemical_list: D002214:Capsules; D005938:Glucocorticoids; D019382:Human Growth Hormone; D003907:Dexamethasone; D003345:Corticosterone; D006854:Hydrocortisone