الفهرس 
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Abstract
Cadmium and hexavalent chromium are toxic heavy metals which cause oxidative stress in organisms. Zinc is effective antioxidant. Therefore, the present study concentrates on the potency of zinc to reverse the changes caused by cadmium and chromium intoxication in blood oxidative system and tissues. The experiment was carried out on 126 adult male albino rats which divided randomly into 7 experimental groups and were orally administered anhydrous cadmium chloride (4.4 mg/kg B.wt), sodium dichromate (2.5 mg/kg B.wt) by stomach tube and zinc chloride (300 mg/L drinking water) by giving alone or in combination daily for 45 days and samples were collected at 15, 30 and 45 days after the start time. In compare to the contro group, the results of serum analysis revealed that the treatment with cadmium and chromium lead to marked increase in the level of lipid peroxidation (expressed by MDA level), activities of hepatic marker enzymes (AST and ALT) and urea and creatinine concentrations. Also, lead to decrease in the activities of antioxidant enzymes (SOD, CAT and GPx) and the level of GSH. Hematological findings revealed significant decrease in RBCs count, Hb concentration and PCV values indicating anemia in cadmium and chromium treated groups and the histopathological examination revealed degenerative and necrotic changes in liver, kidney and testis. Treatment with zinc significantly reversed the changes induced by cadmium and chromium exposure in all examined parameters.
These results indicate that cadmium and hexavalent chromium lead to anemia and tissues damage by oxidative stress induced by the generation of ROS. The interaction between both metals can partially reduce their toxicity. On the other hand, zinc can act as a potent antioxidant and prevent the oxidative damage induced by cadmium and hexavalent chromium.