| Objectives Vitamin E is an essential fat-soluble vitamin that has antioxidant activities. But it had not been reported definitely whether supplementation of high dose vitamin E would cause adverse effects. In this in vivo study we investigated the influence of different levels of high dose vitamin E on oxidative damage of macromolecule and cell function to determine its effect when used excessively.Methods 48 Wistar rats , 60~90g body weight(half male and half female) were randomly divided into 4 groups based on body weight. The control group was fed with normal rat diet which contented vitamin E 75 IU/kg and the other three interfered groups were supplemented with different levels of high dose all-rac-a-tocopheryl acetate enriched diets which contented vitamin E 500 IU/kg,2000 IU/kg,7500IU/kg,respectively. The period of the trial was about 8 weeks. Urine of each rat was collected one week before the end of the trail. At the end of the trial, the rat will be died without pain by drug anesthesia, and samples of the whole blood were collected for analysis. Antioxidation activity analysis included DNA oxidative damage induced by H2O2, activities of serum superoxide dismutase (SOD), glutatathione peroxidase (GSH-Px) content of malanydiadehyde(MDA) and the concerntration of O6-methylguanine in urine. The comet assay or the alkaline single cell gel electrophoresis (SCGE) assay was used to measure the DNA oxidative damage. High performance capillary zone electrophoresis was used to determine O6-methylguanine. SOD, GSH-Px and MDA were measured by biochemical methods with the kits. Cell function a-nalysis included the erythrocyte membrane fluidity and the lymphocyte transformation rate . The method of fluorescence polarization was used to measure membrane fluidity and MTT was used to detected the lymphocyte transformation rate which reflected proliferation activity of immune cell.Results Relatively high dose vitamin E could significantly increase antioxidation activity and cell function detected by lymphocyte proliferation and membrane fluidity . Compared with the control group, 500IU/kg VE increased serum VE by 69. 2%, serum SOD activity by 11% , serum and membrane GSH-Px activities by 5. 4% and 101. 5% while serum MDA decreased by 34%. 500IU/kg VE significantly lowered DNA oxidative damageinduced by 10 tmol/L H2O2 and urine O6-methylguanine was also decreased. After 500IU/ kg VE supplementation with 8 weeks , the erythrocyte membrane fluidity and lymphocyte transformation rate were significantly increased.It worth notion that long term supplementation with too excessive vitamin E would damage macrobiomolecule and decrease cell function. 2000 IU/kg,7500 IU/kg vitamin E increased serum VE by 93. 7%, 117. 4% respectively. But serum SOD activities were decreased by 17% and 18% respectively and DNA oxidative damages induced by 10 mol/L H2O2 were both aggravated in this two groups. At the same time, lymphocyte transformation rate of the rat supplemented with 7500 lU/kg VE for 8 weeks was significantly decreased.Conclusion (1)500 lU/kg vitamin E could increase the activities of antioxidant enzymes such as SOD,GSH-Px and decrease the formation of serum MDA. DNA oxidative damage induced by H2O2 and DNA alkyl damage were decreased by 500 lU/kg VE . As to cell function, 500 lU/kg VE significantly improved membrane fluidity and promoted lymphocyte transformation. (2)2000 IU/kg,7500 IU/kg vitamin E decreased serum SOD activities and aggravated DNA oxidative damages induced by H2O2. Lymphocyte transformation rate was decreased by 7500 IU/kg VE.Above all, relatively high dose vitamin E could increase antioxidation activity of the body and increase cell function indexes such as membrane fluidity and lymphocyte proliferation rate. However, too excessive vitamin E would induce macrobiomolecule damage and decrease cell function.
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