No abstract

Free radicals, hydroxyperoxides and H 2 O 2 are all known to damage cell components. This study was designed to compare the concentrations of hydroxyperoxide and free radical scavengers in the cardiac muscles of old rats in the hyper-or hypothyroid condition, to determine whether rates of peroxidation would differ with age, thyroid status, or both.Rats were rendered hyper-or hypothyroid by administration of -thyroxine or methimazole for 4 weeks. Among the old rats, the lipid peroxide (LPO) concentrations, measured as thiobarbituric acid (TBA) reactants, were significantly greater in the hyperthyroid than in the euthyroid state and the LPO concentrations measured as TBA+Fe 3+ reactants, which may be precursors of LPO, were significantly greater in the hyperthyroid state, whereas in young rats, the LPO concentrations measured by TBA or TBA+Fe 3+ methods did not differ significantly in the hyperthyroid state. In the euthyroid state, the concentration of LPO measured as TBA+Fe 3+ reactants was significantly reduced with age. Xanthine oxidase (XOD) activity also was markedly increased with age, being more pronounced in the hyperthyroid than in the euthyroid state. The Mn and Cu/Zn superoxide dismutase activities were greater in the hyperthyroid than in the euthyroid state. Glutathione peroxidase activity decreased with age in the euthyroid and, particularly, in the hyperthyroid state. Catalase activity was not affected in the old rats. Concentrations of -tocopherol in the old rats were high in the hyperthyroid state and low in the hypothyroid state, whereas the levels of -and -tocopherols in these rats were unchanged in both conditions as compared with the euthyroid state findings.Data suggest that the site of free radical generation differs in older rats, with additional shifts in the location of intracellular lipid peroxidation being noted during hyperthyroidism. Thus, as rats age, the reduction of the free radical scavenger system and the increase in LPO and XOD activities might induce myocardial dysfunction.

No abstract

To clarify whether the changes of free radicals and its scavengers are induced by thyroid disorders, we measured levels of free radical scavengers and checked °2 radical generating systems in the human thyroid gland.Thyroid specimens from patients with Graves' disease, follicular adenoma, and papillary and follicular carcinomas contained significantly higher concentrations of xanthine oxidase (XOD) and gluthathione peroxidase (GSH-PX), compared to those in the normal thyroid tissue. Catalase concentration was significantly lower in thyroid specimens from patients with Graves' disease and significantly lower in thyroid specimens from patients with follicular adenoma, compared to those in the normal thyroid tissue. Cu/Zn superoxide dismutase (CuIZn SOD) concentration was significantly lower in the specimens from follicular adenoma and papillary carcinoma and Mn SOD concentration was significantly higher in the specimens from papillary carcinoma than those in the normal thyroid tissue. The lipid peroxide concentration, expressed as malondialdehyde (MDA) concentration, was significantly higher in the specimens from papillary carcinoma than those in the normal thyroid tissue.These findings suggest that the levels of free radicals are increased and are scavenged and catalyzed in the thyroid of Graves' disease, whereas free radicals and lipid peroxide are not completely scavenged in papillary carcinoma tissues, suggesting that these substances affect some role in cell function of thyroid tumors.

To clarify the effect of glucocorticoid on glucose transporters (GLUT) in adipocytes and muscle, we examined the changes of GLUT4 in rat heart muscle, skeletal muscle and adipocytes during long-term administration of dexamethasone and the translocation of GLUT4. The levels of GLUT4 in the plasma membrane and the low-density microsome fraction were measured by Western blotting using anti-GLUT4 peptide antibody. The levels of GLUT4 in the heart and skeletal muscles of rat were unchanged by treatment of dexamethasone. In the adipocytes the level of GLUT4 in plasma membrane was changed, but it was decreased in the low-density microsome fraction. Although adipocytes are less involved in blood sugar regulation than skeletal muscle, this finding suggests that glucose metabolism in Cushing's syndrome is affected partly by a decrease of GLUT4 in the adipocytes.