Inhibition of Corticosterone Secretion by Thyroxine in Male Rats

Yen-Hao Chen ； Ming-Jae Lo ； Mei-Mei Kau ； Shiow-Chwen Tsai ； Yu-Chung Chiao ； Jiann-Jong Chen ； Charlie Liaw ； Chien-Chen Lu ； Bu-Pian Lee ； Si-Chih Chen ； Victor. S. Fang ； Low-Tone Ho ； Paulus S. Wang

《The Chinese Journal of Physiology》 40卷1期 (1997/03) Pp. 25-30

並列摘要

The effects of thyroxine (T4) on the secretion of corticosterone both in vivo and in vitro in male rats were studied. Rats were thyroidectomized (T(subscript X)) or sham T(subscript X). The T(subscript X) rats were subcutaneously with T4 (20 μ/kg) or saline once daily for two weeks. In an in vitro experiment, adrenal glands were incubated with ACTH, T4, or ACTH plus T4 in the presence or absence of 0.5 mM 3-isobutyl.1-methylxanthine (IBMX) at 37℃ for 60 min. Medium and ether-extracted plasma samples were analyzed for corticosterone by radioimmunoassay (RIA). The accumulation of cyclic adenosine monophosphate (cAMP) in adrenal tissues after incubation with IBMX was measured by RIA. The levels of plasma corticosterone in T(subscript X) rats were significantly increased as compared with euthyroid rats. T4 replacement in T(subscript X) rats restored plasma corticosterone to euthyroid level. Administration of T4 in vitro resulted in an inhibition of both basal and ACTH-stimulated release of corticosterone. Both basal and ACTH-stimulated generations of cAMP in adrenal tissues were decreased by T4. These results suggest that T4 inhibits the spontaneous and ACTH-stimulated secretion of corticosterone by acting directly at adrenal glands via a decrease in cAMP production.

並列關鍵字

corticosterone ； T4 ； cAMP ； adrenal ； plasma ； in vitro