DEXAMETHASONE INCREASES GROWTH-HORMONE (GH)-RELEASING HORMONE (GRH) RECEPTOR MESSENGER-RNA LEVELS IN CULTURED RAT ANTERIOR-PITUITARY-CELLS

Citation
M. Tamaki et al., DEXAMETHASONE INCREASES GROWTH-HORMONE (GH)-RELEASING HORMONE (GRH) RECEPTOR MESSENGER-RNA LEVELS IN CULTURED RAT ANTERIOR-PITUITARY-CELLS, Journal of neuroendocrinology, 8(6), 1996, pp. 475-480
Citations number
42
Categorie Soggetti
Neurosciences,"Endocrynology & Metabolism
ISSN journal
09538194
Volume
8
Issue
6
Year of publication
1996
Pages
475 - 480
Database
ISI
SICI code
0953-8194(1996)8:6<475:DIG(H(>2.0.ZU;2-A
Abstract
To examine the effects of glucocorticoid (Gd) on growth hormone (GH)-r eleasing hormone (GRH) receptor gene expression, a highly-sensitive an d quantitative reverse-transcribed polymerase chain reaction (RT-PGR) method was used in this study. Rat anterior pituitary cells were isola ted and cultured for 4 days. The cultured cells were treated with dexa methasone for 2, 6, and 24 h. GRH receptor mRNA levels were determined by competitive RT-PCR using a recombinant RNA as the competitor. Dexa methasone significantly increased GRH receptor mRNA levels at 5 nM aft er 6- and 24 h-incubations, and the maximal effect was found at 25 nM. The GC receptor-specific antagonist, RU 38486 completely eliminated t he dexamethasone-induced enhancement of GRH receptor mRNA levels. Dexa methasone did not alter the mRNA levels of beta-actin and prolactin at 5 nM for 24 h, whereas GH mRNA levels were significantly increased by the same treatment. The GH response to GRH was significantly enhanced by the 24-h incubation with 5 nM dexamethasone. These findings sugges t that GC stimulates GRH receptor gene expression through the ligand-a ctivated GC receptors in the rat somatotrophs. The direct effects of G C on the GRH receptor gene could explain the enhancement of GRH-induce d GH secretion.