Interactions of Methionine, Vitamin E, and Antioxidants in Selenium Toxicity in the Rat1

Abstract

Female Wistar albino rats were fed a low vitamin E diet based on peanut meal and containing 10 ppm selenium as Na₂SeO₄. Supplementation of the diet with either 0.5% dl-methionine (Met) or 0.05% dl-α-tocopheryl acetate (E) alone gave little protection against the liver damage due to selenium. However, a combination of 0.5% Met plus 0.01 to 0.05% E gave increasingly better protection depending on the level of E added. Combinations of 0.5% Met plus 0.05% N,N′-diphenyl-p-phenylenediamine, 1,2-dihydro-6-ethoxy-2,2,4-trimethylquinoline, or butylated hydroxytoluene were also effective against liver damage, whereas supplements of 0.5% Met plus 0.1% disodium ethylenediaminetetraacetate, 0.25% methylene blue, or 0.5% ascorbic acid gave little or variable protection against selenium. Replacement of the 0.5% Met with equimolar amounts of cysteine, betaine, or cysteine plus betaine gave variable results. Addition of 0.39% guanidoacetic acid to a diet supplemented with 0.5% Met and 0.05% E appeared to inhibit the protective effect of the Met-E combination. Selenium levels in the livers and kidneys of rats fed supplements which protected against selenium poisoning were lower than those of the animals fed the unsupplemented seleniferous peanut meal diet. It is suggested that vitamin E and the fat-soluble antioxidants make the methyl group of methionine more available for selenium detoxification.