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Horm Metab Res 1975; 7(3): 222-227
DOI: 10.1055/s-0028-1093743
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© Georg Thieme Verlag KG Stuttgart · New York

T3/T4 Ratios and α-Glycerophosphate Activity in Intact Rats Exposed to a Cold Environment

J.  Bernal , F. Escobar del Rey
  • Departamento de Endocrinologia Experimental, Instituto G. Marañón, Centro de Investigaciones Biológicas, C.S.I.C., Madrid, Spain
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Publication Date:
23 December 2008 (online)

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Abstract

The quantitative distribution of I-containing compounds has been studied in the thyroid and different tissues of intact rats, equilibrated isotopically with I125 and exposed to 4-10°C for two weeks. It was found that the T3/T4 ratio was increased in extrathyroidal samples. The T3/T4 ratio in the intrathyroidal pool of "free" iodothyronines also tended to increase. In the liver, but not in the kidney, of cold-exposed rats, the concentrations of T3 was higher, and the concentration of T4 the same, or lower. The α-GPD activity increased in the liver, but not in the kidney of similarly treated animals. A positive correlation was found between α-GPD activity and T3 concentration, but not between α-GPD and the concentration of T4. These and previous findings support the idea that conversion of T4 to T3 plays an important role in the expression of a biological effect of T4.

Key words

Thyroxine - Triiodothyronine - α-GPD - Cold- Exposure - Rats - Isotopic Equilibrium