Effect of selenium deficiency on liver and blood glutathione peroxidase activity in the black bullhead

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Abstract
Male black bullheads, approximately 4 gm, were fed a selenium‐deficient torula yeast‐based diet for 18 weeks, and the activity of glutathione peroxidase was studied in liver and blood using H2O2 as a substrate. Controls were on the same diet, but received weekly intraperitoneal injections of Na2SeO3. At 12 and 18 weeks significant decreases in blood and liver glutathione peroxidase activity were observed in the experimental animals. Liver showed an even greater decrease than blood in glutathione peroxidase activity in the selenium‐deficient animals. Females (4 gm) kept on the diet for 15 weeks showed similar results. Liver activities were not decreased nearly as much when cumene hydroperoxide was used as the substrate instead of H2O2. This indicates that at least two glutathione peroxidase activities are present in fish liver. One is selenium dependent; its activity, as measured with H2O2 as substrate, becomes almost undetectable in selenium‐deficient fish. This situation is very similar to that found in mammalian species.