Effects of Short- and Long-Term Dexamethasone Treatment on Growth and Growth Hormone (GH)-Releasing Hormone (GRH)-GH-Insulin-Like Growth Factor-I Axis in Conscious Rats

Endocrine Journal

NAOMI HIZUKA²  TOMOYO OHYAMA¹  JIRO TAKAHARA¹  MICHIO NIIMI³  MAKOTO SATO¹ 

[1] First Department of Internal Medicine, Kagawa Medical University;Tokyo Women's Medical School;Department of Clinical Laboratory Medicine, Kagawa Medical University

关键词: Dexamethasone;    GH;    Insulin-like growth factor-I (IGF-I);    GRH receptor;    Rat;   

DOI  :  10.1507/endocrj.44.827

学科分类：内分泌与代谢学

来源: Japan Endocrine Society

【 摘 要 】

References(39)Cited-By(5)Although the inhibitory effects of a chronic excess of glucocorticoids (GC) on body growth and GH secretion are well established, the mechanisms involved remain unclear. In this study, we examined the chronic effects of a high dose of dexamethasone (DEX) on spontaneous GH secretion and insulin-like growth factor (IGF)-I in conscious rats. The animals were given daily ip injections of DEX (200μg/day) for either one or four weeks. Body growth assessed by tibia length and serum IGF-I levels was significantly inhibited 1 week after treatment. By contrast, spontaneous GH secretion was not altered 1 week after the treatment. Neither hypothalamic GRH and somtatostain mRNA levels nor GH responses to GRH from single somatotropes were affected 1 week after the treatment. Four weeks after DEX treatment, body growth of the rats was noticeably suppressed. Interestingly, spontaneous GH secretion, hypothalamic GRH mRNA levels and GH responses to GRH were all inhibited 4 weeks after treatment. Pituitary GRH receptor mRNA levels were not altered 1 week after treatment, but increased after 4 weeks. These results indicate that a high dose of DEX initially impairs IGF-I production and subsequently inhibits spontaneous GH secretion in rats. Inhibition of spontaneous GH secretion resulting from chronic GC excess is due, at least in part, to the impairment of hypothalamic GRH synthesis and pituitary GH responsiveness. An increase in the pituitary GRH receptor may be caused by decreased GRH secretion.

【 授权许可】

Unknown