Effects of triiodothyronine administration on the adenylyl cyclase
system in brown adipose tissue of rat.
Administration, T, and Adenylyl Cyclase System.
ADLI , R. BAZIN, R. VASSY AND G. Y. PERRET
APStracts 4:0081E, 1997.
This study was undertaken to investigate the effect of
triiodothyronine (T3) administration to euthyroid rats upon 3
-adrenoceptor (3-AR) expression and upon the different components of
the adenylyl cyclase (AC) system in brown adipose tissue (BAT). In
rats treated with T3, the 3-AR density (assessed by the binding of
[3H]CGP12177) showed a decrease of 50%, as did their mRNA, as
analyzed by RT-PCR. In hyperthyroid rats, as compared to control
rats, there was a 40% increase in Gsa activity (stimulated by NaF or
GTPgs) and a 4-fold increase in the protein concentration (Western
blotting). In contrast, the level of the pertussis toxin substrate Gi
declined by 35% in response to T3. Analysis of dose response curves
for isoproterenol and CGP12177 revealed that neither basal nor
stimulated AC activities, nor IC50 for these agonists, were changed
by T3 administration. In conclusion, these results suggest that down
-regulation of the 3-AR by T3 was counterbalanced by changes in other
components of the AC cascade (i.e. Gs and Gi), so that no change
occurred in the capacity of BAT to generate cAMP.
Received 31 January 1997; accepted in final form 2 April 1997.
APS Manuscript Number E46-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 15 April 1997