Acute effects of thyroid hormones on the production of adrenal camp
and corticosterone in male rats.
Lo, Ming-Jae, Mei-Mei Kau, Yen-Hao Chen, 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, and Paulus S. Wang.
Department of Physiology, National Yang-Ming University, Department
of Biology, Fu-Jen Catholic University and Department of Medical
Research and Education, Veterans General Hospital-Taipei, Taipei,
Taiwan, Republic of China
APStracts 4:0241E, 1997.
The acute effects of thyroid hormones on glucocorticoid secretion were
studied. Venous blood samples were collected from male rats after
they received intravenous triiodothyronine (T3) or thyroxine (T4).
Zona fasciculata-reticularis (ZFR) cells were treated with
adrenocorticotropic hormone (ACTH), T3, T4, ACTH plus T3 or ACTH plus
T4 at 37 SYMBOL 176 \f "Times New Roman"C for 2 h.
Corticosterone concentrations in plasma and cell media, and also
adenosine 3',5'-cyclic monophosphate (cAMP) production in ZFR cells
in the presence of 3-isobutyl-1-methylxanthine, were determined. The
effects of thyroid hormones on the activities of steroidogenic
enzymes of ZFR cells were measured by the amounts of intermediate
steroidal products separated by thin-layer chromatography.
Administration of T3 and T4 suppressed the basal and the ACTH
-stimulated levels of plasma corticosterone. In ZFR cells, both
thyroid hormones inhibited ACTH-stimulated corticosterone secretion,
but the basal corticosterone was inhibited only with T3 > 10-10 M
or T4 > 10-8 M. Likewise, T3 or T4 at 10-7 M inhibited the basal-
and ACTH-stimulated levels of intracellular cAMP. Physiological doses
of T3 and T4 decreased the activities of 3SYMBOL 98 \f
"Symbol"-hydroxysteroid dehydrogenase, 21-hydroxylase and
11SYMBOL 98 \f "Symbol"-hydroxylase. These results suggest
that thyroid hormones counteract ACTH in adrenal steroidogenesis
through their inhibition of cAMP production in ZFR cells.
Received 18 March 1997; accepted in final form 29 October 1997.
APS Manuscript Number E120-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 14 November 1997