Relative antioxidant effectiveness of alpha-tocopherol and gamma-tocopherol in iron-loaded rats.

The relative antioxidant effectiveness of RRR-alpha-tocopherol and d-gamma-tocopherol against in vivo lipid peroxidation in vitamin E-depleted, iron-loaded rats was assessed by measurement of expired pentane. Rats fed a vitamin E-deficient diet were each administered 103 +/- 2 mg of iron as iron dextran over a 4-week period. After 3 weeks, their erythrocytes were 96.9 +/- 0.6% hemolyzed by dialuric acid. After 6 weeks, the rats exhaled 22.4 +/- 3.4 pmol pentane/(100 g body weight . minute). Groups of 4 rats each were then fed varying levels of RRR-alpha- and d-gamma-tocopherol for 2 weeks, after which the pentane levels were directly related to the dietary tocopherol content. Covariance analysis of the log of pentane production versus the log of dietary tocopherol showed the relative antioxidant effectiveness of 1:0.31 for alpha-tocopherol:gamma-tocopherol. In an independent estimation of relative antioxidant effectiveness, covariance analysis of the log of lipid soluble fluorophores in the spleens of the rats versus the log of dietary tocopherol showed a ratio of 1:0.37 for alpha-tocopherol:gamma-tocopherol. Regression analysis showed the fluorophores also to be correlated with the integrated amount of pentane produced over the 7-week experiment (r = 0.84, P less than 0.001). gamma-Tocopherol was more effective as an in vivo antioxidant than has been reported for its inhibition of vitamin E-deficiency syndromes.