Protective effects of oleanolic acid and vitamine E on thyroid dysfunction and lipid peroxidation in cadmium- induced toxicity in rats

The effect of oleanolic acid or vit. E on heavy metal [cadmium] -induced thyroid dysfunction and lipid peroxidation in male rats was studied. The animals divided into 3 groups each of which 6 rats. The first group were injected with 1mg/kg/day cadmium chloride, 1% solution in distilled water subcutaneously daily for 30 days. The second group were injected simultaneously with equivalent dose of cadmium chloride [1mg/kg/day] subcutaneously and oleanolic acid in a dose of 5 mg/kg/day, 2% suspension in 2% tween 80 intramuscularly for 30 days. The third group were injected simultaneously with equivalent dose of cadmium chloride [1mg/kg/day] subcutaneously and vit. E, in a dose of 100mg/kg [5% solution in saline] intramuscularly for 30 days. The control groups were divided into 3 groups. The first group was treated with distilled water, the second one was treated with tween 80 and lastly the third group was trated with saline. Cadmium chloride treatment alone led to decrease in concentrations of serum thyroid hormones, zinc and copper concentration [p<0.01]. In addition, a significant increase in both malondialdyhyde [MDA] levels and thyroid stimulating hormone [TSH] has been observed by Cd-treatment alone [p<0.01]. Treatment with either oleanolic acid or vit.E improved the metal-induced decrease in serum thyroid function. Treatment with oleanolic acid lead to decrease in levels of blood and hepatic malondialdyhyde but remain higher than normal rates [47.14 +/- 0.82 micro mol/L and 119 +/- 0.86 micro mol/g wet tissue, respectively]. However, treatment with Cd and vit. E restored blood and hepatic malondialdyhyde levels toward normal values [34.7 +/- 0.65 micro mol/L and 100.4 +/- 1.44 micro mol/g wet tissue, respectively]. The effect of vit. E combined with cadmium is significant compared with the effect of oleanolic acid treatment with cadmium [p<0.01]. The protective effect of each oleanolic acid or vit. E against cadmium-induced thyroid dysfunction is mediated through its antioxidative action