BODY-TEMPERATURE AND THYROID-HORMONE METABOLISM OF COPPER-DEFICIENT RATS

The hypothesis that the effects of copper deficiency on body temperatu re 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 mu mol/kg), marginal (31.5 mu mol/kg), or deficient (<7.9 mu mol/kg) amounts of copper for 35 da ys. Anemia was not found in the copper-restricted groups. Plasma chole sterol concentrations increased (P < 0.05) and plasma copper, cerulopl asmin, and liver copper concentrations decreased (P < 0.05) in the rat s fed the copper-restricted diet as compared with the copper-adequate diet. Cytochrome c oxidase and glutathione peroxidase activities in li ver and brown adipose tissue were decreased (P < 0.05) in the copper-d eprived rats. Body temperatures at 24 degrees C were less (P < 0.05) i n the severely copper-deficient as compared with the moderately copper -deficient and copper-adequate animals. Plasma thyroxine concentration s were decreased (P < 0.05) in severely copper-deficient as compared w ith moderately copper-deficient and copper-adequate rats. Plasma tri-i odothyronine concentrations were reduced (P < 0.05) and plasma thyroid -stimulating hormone concentrations were elevated (P < 0.05) in both g roups of copper-restricted rats relative to the copper-adequate rats. Thyroxine 5'-monodeiodinase activities in liver and brown adipose tiss ue were decreased (P < 0.05) in the copper-restricted animals. Hepatic tri-iodothyronine receptors were increased (P < 0.05) by dietary copp er restriction. Body fatness was greater (P < 0.05) in copper-restrict ed 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 degrees C.