Cold exposure rapidly induces virtual saturation of brown adipose tissue nuclear T sub 3 receptors

Journal Article · Sat Oct 01 00:00:00 EDT 1988 · American Journal of Physiology; (USA)

OSTI ID:6252798

Bianco, A C; Silva, J E ^[1]

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1. Univ. of Sao Paulo (Brazil) Harvard Medical School, Boston, MA (USA)

Cold exposure induces a rapid increase in uncoupling protein (UCP) concentration in the brown adipose tissue (BAT) of euthyroid, but not hypothyroid, rats. To normalize this response with exogenous 3,5,3{prime}-triiodothyronine (T{sub 3}), it is necessary to cause systemic hyperthyroidism. In contrast, the same result can be obtained with just replacement doses of thyroxine (T{sub 4}) and, in euthyroid rats, the normal response of UCP to cold occurs without hyperthyroid plasma T{sub 3} levels. Consequently, the authors explored the possibility that the cold-induced activation of the type II 5{prime}-deiodinase resulted in high levels of nuclear T{sub 3} receptor occupancy in euthyroid rats. Studies were performed with pulse injections of tracer T{sub 3} or T{sub 4} in rats exposed to 4{degree}C for different lengths of time (1 h-3 wk). Within 4 h of cold exposure, they observed a significant increase in the nuclear ({sup 125}I)T{sub 3} derived from the tracer ({sup 125}I)T{sub 4} injections (T{sub 3}(T{sub 4})) and a significant reduction in the nuclear ({sup 125}I)T{sub 3} derived from ({sup 125}I)T{sub 3} injections (T{sub 3}(T{sub 3})). The number of BAT nuclear T{sub 3} receptors did not increase for up to 3 wk of observation at 4{degree}C. The mass of nuclear-bound T{sub 3} was calculated from the nuclear tracer ({sup 125}I)T{sub 3}(T{sub 3}) and ({sup 125}I)T{sub 3}(T{sub 4}) at equilibrium and the specific activity of serum T{sub 3} and T{sub 4}, respectively. By 4 h after the initiation of the cold exposure, the receptors were >95% occupied and remained so for the 3 weeks of observation. They conclude that the simultaneous activation of the deiodinase with adrenergic BAT stimulation serves the purpose of nearly saturating the nuclear T{sub 3} receptors. This makes possible the realization of the full thermogenic potential of the tissue without causing systemic hyperthyroidism.

• OSTI ID: 6252798
• Journal Information: American Journal of Physiology; (USA), Vol. 255:4; ISSN 0002-9513
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ADIPOSE TISSUE
TEMPERATURE EFFECTS
RECEPTORS
BIOCHEMICAL REACTION KINETICS
THYROXINE
RADIORECEPTOR ASSAY
TRIIODOTHYRONINE
HYPERTHYROIDISM
RATS
AMINO ACIDS
ANIMAL TISSUES
ANIMALS
BODY
CARBOXYLIC ACIDS
CONNECTIVE TISSUE
DISEASES
ENDOCRINE DISEASES
HORMONES
ISOTOPE APPLICATIONS
KINETICS
MAMMALS
MEMBRANE PROTEINS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC IODINE COMPOUNDS
PEPTIDE HORMONES
PROTEINS
REACTION KINETICS
RODENTS
THYROID HORMONES
TISSUES
TRACER TECHNIQUES
VERTEBRATES
551001* - Physiological Systems- Tracer Techniques