CONCENTRATIONS OF THYROID-HORMONES IN SERUM AND ACTIVITY OF HEPATIC 5'MONODEIODINASE IN COPPER-DEFICIENT RATS

The aim of the present study was to investigate the effect of copper d eficiency on thyroid hormone metabolism in rats. Therefore, an experim ent with growing male Sprague-Dawley rats was carried out, consisting of two groups of rats fed either a copper-deficient (0.06 mg Cu/kg) or a copper-adequate diet (16 mg Cu/kg). Both groups of rats were fed id entical quantities of diet by pair-feeding. Copper deficiency decrease d the final body weight of the rats by 5 % compared to copper-adequate control rats. A severe copper-deficient state in the rats fed the cop per-deficient diet was proved by a large decrease of ceruloplasmin act ivity in serum (by 97 %) and hematological changes. For estimation of thyroid hormone metabolism, the concentrations of total and free thyro xine (T-4) and triiodothyronine (T-3) in serum and the activity of hep atic 5'monodeiodinase (5'D) were determined. Copper-deficient rats had an increased concentration of T-3 in serum, whereas the concentration s of total and free T-4 as well as the activity of hepatic 5'D were no t different compared with copper-adequate control rats. Therefore, the study shows that copper deficiency has only slight effects on thyroid hormone metabolism in growing rats.