The Effects of Zinc Sulfate on the Levels of Some Elements and Oxidative Stress Occurring in Lenses of Rats Exposed to Total Cranium Radiotherapy

Objective. There is currently substantial clinical interest in zinc (Zn) as an antioxidant and a protective agent against radiation-related normal tissue injury. To further assess the potential antioxidative effects, the effects of Zn were studied in rat lenses, a model of radiation- induced oxidative stress.

Materials and Methods. Sprague-Dawley rats were divided into three equal groups. Group 1 received neither Zn nor irradiation (control group). Group 2 (RT group) and 3 (RT+Zn group) were exposed to total cranium irradiation of 5 Gy in a single dose by using a cobalt-60 teletherapy unit. In addition to irradiation, group 3 was administered 10 mg/kg/day Zn. At the end of 10 days, the rats were killed. Their eyes were enucleated to measure the activities of antioxidant enzymes and the levels of iron, calcium, sodium and potassium.

Results. Irradiation significantly increased malondialdehyde levels as an end product of lipid peroxidation, glutathione peroxidase activity, and iron and calcium concentrations. Irradiation decreased superoxide dismutase activities and zinc concentrations in the rat lens, indicating an increased oxidative stress generated by the decomposition of water and/or Fenton reaction. Malondialdehyde levels and iron and calcium concentrations were significantly decreased, and superoxide dismutase and glutathione peroxidase activities and zinc concentrations were increased, in the rat lenses of the RT+Zn group. No differences were detected inany final measurement of sodium and potassium in the direct comparison among all groups.

Conclusion. Zinc, acting as an antioxidant agent, may protect the lens from radiation-induced injury by improving oxidative stress generated by the decomposition of water and/or Fenton reaction.