EFFECTS OF THYROID-HORMONE ON COENZYME-Q AND OTHER FREE-RADICAL SCAVENGERS IN RAT-HEART MUSCLE

Active oxygen species are reported to cause organ damage. This study w as therefore designed to determine the behaviour of antioxidants and f ree radical scavengers so as to reveal changes in animals in the hyper - and hypothyroid state.Levels of antioxidant factors (i.e. coenzyme Q (CoQ)10, CoQ9 and vitamin E) and free radical scavengers (catalase, g lutathione peroxidase (GSH-PX) and superoxide dismutase (SOD)) were me asured in the heart muscles of rats rendered hyper- or hypothyroid by 4 weeks of thyroxine (T-4) or methimazol treatment. Serum levels of Co Q9 and total SOD were also measured. A significant reduction in CoQ9 l evels was observed in the heart muscles of both hyper- and hypothyroid rats when compared with control hearts. There was no difference in se rum CoQ9 levels in thyroid dysfunction when compared with control anim als. Levels of vitamin E in the heart muscles of hyperthyroid rats wer e significantly increased, and there was no reduction in vitamin E lev els in hypothyroid rats when compared with control hearts. GSH-PX leve ls in the heart muscle were reduced in hyperthyroid rats and increased in hypothyroid rats when compared with control hearts. However, there were no differences in catalase levels in heart muscle between hyper- and hypothyroid rats. The concentration of SOD in heart muscle was in creased in hyperthyroid rats and was not decreased in hypothyroid rats compared with control rats, suggesting the induction of SOD by excess ive production of O-2(-). These data suggest that the changes in these scavengers have some role in cardiac dysfunction in the hyper- and hy pothyroid state in the rat.