T3 potentiates the adrenergic stimulation of type ii 5' deiodinase
activity in cultured rat brown adipocytes.
Hernandez, A., and M. J. Obregon.
Unidad de Endocrinolog[acute]ia Molecular, Instituto de
Investigaciones Biom[acute]edicas, Consejo Superior de
Investigaciones Cient[acute]ificas (C.S.I.C.), Madrid, Spain
APStracts 3:0035E, 1996.
Iodothyronine type II-5'Deiodinase (5'D-II) activities were studied in
cultures of rat brown adipocytes. In the presence of serum, the
adrenergically stimulated 5'D-II activities were very low. In the
absence of serum, cAMP analogs stimulated 5'D-II activity. T4
inhibited these increases. Norepinephrine slightly increased 5'D-II
activity in hypothyroid conditions, but T3 strongly potentiated the
adrenergic stimulation of 5'D-II (20-fold). T3 amplification of the
adrenergic stimulation was via [beta]-adrenergic receptors,
specifically mimicked by [beta]3 agonists, but it was not observed
using cAMP analogs. The stimulatory effect of T3 predominated over
the inhibitory action of T4, increased with exposure to T3 and
required de novo protein synthesis. The half-life of 5'D-II was 30
minutes, suggesting that stabilization of 5'D-II did not occur. The
effect was only observed in differentiated adipocytes. Retinoic acid
has similar, although smaller effects than T3. In conclusion, the
presence of T3 is required and strongly potentiates the noradrenergic
stimulation of 5'D-II activity in rat brown adipocytes.
Received 28 August 1995; accepted in final form 30 January 1996.
APS Manuscript Number E417-5.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 14 February 96