Body temperature and thyroid hormone metabolism of copper-deficient rats

Abstract

The hypothesis that the effects of copper deficiency on body temperature are mediated via the thyroid hormone system was examined in 24 male Sprague-Dawley rats, weighing 240 to 250 g, matched by weight and fed ad libitum diets containing adequate (78.7 μmol/kg), marginal (31.5 μmol/kg), or deficient (<7.9 μmol/kg) amounts of copper for 35 days. Anemia was not found in the copper-restricted groups. Plasma cholesterol concentrations increased (P < 0.05) and plasma copper, ceruloplasmin, and liver copper concentrations decreased (P < 0.05) in the rats fed the copper-restricted diet as compared with the copper-adequate diet. Cytochrome c oxidase and glutathione peroxidase activities in liver and brown adipose tissue were decreased (P < 0.05) in the copper-deprived rats. Body temperatures at 24 °C were less (P < 0.05) in the severely copperdeficient as compared with the moderately copper-deficient and copper-adequate animals. Plasma thyroxine concentrations were decreased (P < 0.05) in severely copper-deficient as compared with moderately copperdeficient and copper-adequate rats. Plasma tri-iodothyronine concentrations were reduced (P < 0.05) and plasma thyroid-stimulating hormone concentrations were elevated (P < 0.05) in both groups of copper-restricted rats relative to the copper-adequate rats. Thyroxine 5′-monodeiodinase activities in liver and brown adipose tissue were decreased (P < 0.05) in the copper-restricted animals. Hepatic triiodothyronine receptors were increased (P < 0.05) by dietary copper restriction. Body fatness was greater (P < 0.05) in copper-restricted as compared with copper-adequate rats. These findings indicate that copper deficiency without anemia decreases tissue copper and selenium status and is associated with impaired thyroid hormone metabolism and mild hypothermia in rats at maintained at 24 °C. (J. Nutr. Biochem. 6:445-451, 1995.)