Zinc as an antiperoxidative agent following iodine-131 induced changes on the antioxidant system and on the morphology of red blood cells in rats.

Iodine-131 ((131)I) irradiation is the first line treatment for Graves' disease and thyroid carcinoma. In such cases, (131)I gets accumulated in the thyroid, and is released in the form of radioiodinated triiodothyronine (T3) and tetraiodothronine (T4). Various reports describe changes in the blood picture after radioiodine treatment. Zinc, on the other hand, has been reported to maintain the integrity of red blood cells (RBC) under certain toxic conditions. The present study was conducted to evaluate the adverse effects of (131)I on the antioxidant defense system and morphology of RBC and also to assess the possible protection by zinc under irradiation by (131)I. Thirty two female Wistar rats were equally segregated into four main groups. Animals with Group I served as normal controls; Group II animals were administered a dose of 3.7 MBq of (131)I (carrier free) intraperitoneally, Group III rats were supplemented with zinc (227 mg/L drinking water) and Group IV rats were given a combined treatment of (131)I and zinc, in a similar way as in Group II and IV rats. After seven days of (131)I treatment, RBC lysate was prepared and its antioxidant status assessed. The activity of superoxide dismutase (SOD), reduced glutathione (GSH) and malondialdehyde (MDA) in the lysate of RBC was increased. On the contrary, the activity of catalase was found to be significantly decreased. The activity of glutathione reductase (GR) remained unchanged. Marked changes in the shape of RBC from normal discocytes to echinocytes, spherocytes, stomatocytes and acanthocytes were also observed in the blood of the rats treated with (131)I. Zinc supplementation to (131)I treated rats, significantly attenuated the adverse effects caused by (131)I on the levels of MDA, GSH, SOD and catalase. In conclusion, the study revealed significant oxidant/antioxidant changes in RBC following (131)I administration in rats, while zinc was shown to act as a radioprotector agent.