Thyroid hormones regulate lipid peroxidation and antioxidant enzyme activities in Anabas testudineus (Bloch)

The role of thyroid hormones in metabolic pathways are well known. However. their involvement in lipid peroxidation and antioxidant enzyme activities is not known. In this study, the in vivo injection of h-propylthiouracil (6-PTU) did not alter the concentration of malondialdehyde (MDA) and conjugated dienes in liver. The administration of triiodothyronine (T-3) or diiodothyronine (T-2) increased the peroxidation rate in hyporhyroid fish. However, in normal fish, only a high dose of T2 caused increased malondialdehyde (MDA) production, rather than T-3. SOD activity was higher in T-2-treated groups in both experiments. Glutathione peroxidase (GPx) activity was also high in hypothyroid fish treated with T-2. In normal specimens, injections of T-3 and T-2 had no effect on GPx activity, Glutathione: reductase (GR) activity was not altered by hypothyroidism while T-3 (1 mug) and T-2 (1 mug) increased it. Glutathione content was low in 6-PTU treated fish and high in both T-3- and T-2-treated groups. Thus it can be concluded that not only T-3 hut also T-2, formed by sequential monodeiodination of T-4, is also effective in influencing lipid peroxidation and antioxidant enzyme activities in Anabas. Furthermore, hypothyroidism as well as hyperthyroidism affects lipid peroxidation in this teleost, (C) 2001 Elsevier Science Inc. Ail rights reserved.