Lipid Antioxidant Activity in Tissues and Proteins of Selenium-fed Animals

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Abstract
Lipid antioxidant activity of lipid-free tissue fractions, from control and selenium-fed chickens, rats, and sheep was studied. Animals were fed 10 or 14 ppm of selenium supplied either as sodium selenite or sodium selenate added to a nutritionally adequate basal ration. Antioxidant activities of the tissue fractions were tested by manometric and polarographic techniques. The protein contents of the tissue fractions varied from 82 to 100% and the selenium-fed animal tissue fractions contained levels of selenium ranging from 13 to 24 ppm. Antioxidant activity expressed as protective indices varied from 1.0 to 6.0 indicating antioxidant activity for all selenium kidney and liver fractions tested except rat liver. Kidney fraction from sheep contained the highest antioxidant activity. Addition of hemoglobin to the manometric system increased the total oxygen consumption but did not greatly influence the protective indices of the selenium tissue fractions. Addition of α-tocopherol to the control and selenium tissue fractions decreased the total oxygen consumption, did not greatly affect the protective indices, and appeared to exert its antioxidant effects largely independent of the selenium antioxidant. Antioxidant activity was shown to be associated with the tissue selenoproteins. Selenium antioxidants were found to possess 500 times the antioxidant activity of α-tocopherol by the polarographic method and 50 to 100 times in the manometric method. Synergism between α-tocopherol and the tissue selenium was not large. Mechanisms to explain the antioxidant action of selenium in the animal body are presented.