Protein oxidation in thyroid hormone-induced liver oxidative stress: relation to lipid peroxidation

The influence of thyroid hormone administration (daily doses of 0.1 mg of 3 ,3 ',5-triiodothyranine (T-3)/kg for 1-3 consecutive days) on rat liver pro tein oxidation was investigated in relation to the calorigenic and lipid pe roxidative actions of the hormone. T-3 treatment elicited a progressive enh ancement in the serum levels of the hormone, the rectal temperature of the animals, and in the rate of O-2 uptake of the liver, changes that are signi ficantly correlated and evidence the development of thyroid calorigenesis. Liver lipid peroxidation was augmented by T-3 administration as determined by the tissue content of thiobarbituric acid reactants, with a maximal effe ct (3.1-fold increase) being found at 2 days after treatment, whereas prote in oxidation measured by the content of protein hydrazone derivatives exhib ited a maximal 88% increase at 3 days. Maximal rates of lipid peroxidation occur at 1 day after the administration of T-3, whereas those of protein ox idation are attained after treatment with three daily doses of T-3, time at which the former levels off. It is concluded that T-3 administration induc es a substantial enhancement in hepatic protein oxidation, in addition to l ipid peroxidation, that seems to be due to the higher oxidative stress stat us conditioned in the liver by thyroid calorigenesis. Both processes exhibi t a differential time course of changes, that may represent differences in the susceptibility of target molecules to free radical attack and/or in the efficiency of repair mechamisms. (C) 1999 Elsevier Science Ireland Ltd. Al l rights reserved.