Dietary alpha-tocopherol supplementation on antioxidant defenses after in vivo iron overload in rats

The effect of dietary alpha-tocopherol (alpha-T) supplementation on iron overload-dependent oxidative damage was studied. Male Wistar rats were fed diets supplemented with 2.5% carbonyl iron and/or 200 mg/kg of alpha-tocopheryl acetate for 6 weeks. Oxidation of lipids and proteins were increased by iron overload in rat liver, and alpha-T dietary supplementation effectively prevented these effects. Iron overload decreased both, catalase and Mn-superoxide dismutase activities by 49 and 54%, respectively, with no effect on glutathione peroxidase activity. alpha-T supplementation did not prevent the inhibition measured in catalase and Mn-superoxide dismutase activities. Iron dietary excess had no effect on liver alpha-T and ubiquinol 9 (UQ9) content. Ubiquinol 10 (UQ10) content after iron overload was decreased by 58 and 54% in whole liver and liver mitochondria, respectively. alpha-T supplementation led to significant increases in alpha-T, UQ9 and UQ10 content in liver, as compared to control values, and partially prevented the decrease in UQ10 content due to iron excess. The results presented here indicate that initial stages of iron overload led to oxidative damage in liver (evaluated in terms of lipid and protein oxidation) with a decline in antioxidant defenses. alpha-T supplementation affected the liver content of lipid soluble antioxidants, suggesting a concerted antioxidant response at the cellular level to modulate the effect of excess iron availability. (C) 1997 Elsevier Science Ireland Ltd.