Defense of mouse red blood cells against oxidative damage by phenylhydrazine. Glutathione peroxidase and catalase deficiency

Red cells are constantly exposed to oxidants such as O₂^-, H₂O₂, lipid peroxides, and lipid hydroperoxides. In order to understand the role of various enzymes in the protection of red cells against oxidative damage, SOD, GSH-Px, GSH reductase, and both the catalatic and peroxidatic activities of catalase were determined in acatalasemic, GSH-Px-deficient mice. GSH-Px deficiency was produced in normal and acatalasemic mice by feeding a selenium-deficient diet for about 10 months. GSH-Px levels in the red cells of these animals decreased to less than 10% of normal. The levels of residual catalase in the red cells of the acatalasemic mice were less than 3% of normal. No hematological abnormality was observed in any group of mice except slight reticulocytosis in the acatalasemic mice, irrespective of GSH-Px levels. A deficiency in the catalatic activity of catalase, GSH-Px, or both did not affect the red cell survival. After treatment with phenylhydrazine, a drug known to produce O₂^-, severe reticulocytosis, increased levels of lipid peroxides, and a high fatality rate were observed in the GSH-Px-deficient mice. However, there was no compensatory increase in SOD or GSH reductase activities as a result of either acatalasemia or GSH-Px deficiency or as a result of oxidative challenge. Although the catalatic activity of catalase was deficient in the red cells of the acatalasemic mice (C3H-C_Sb-ANL), the peroxidatic activity of catalase was comparable to that of the normals. It was concluded that acatalasemia in mice may be due to a structural gene mutation leading to the synthesis of altered subunits which exhibit peroxidatic activity but do not combine to form tetramers and express catalatic activity. It is possible that the catalatic activity of catalase does not play a significant role in the protection of the red cell against oxidative damage. Extremely low levels of the catalatic activity of catalse (<3%) and/or GSH-Px (<10%) maintained the integrity of the red cell and its normal survival in the absence of oxidative stress. However, GSH-Px and possibly the peroxidatic activity of catalase are necessary to maintain a reduced atmosphere in the red cell under oxidative stress.