Intracellular catalase function: analysis of the catalatic activity by product formation in isolated liver cells

Intracellular catalase activity was measured in isolated rat hepatocytes by adding H₂O₂ under anaerobic conditions and measuring O₂ evolution. Hydrogen peroxide was introduced either by continuous infusion or by pulse injection. Continuous infusion at a rate similar to the endogenous H₂O₂ production rate provided results that 60–70% of the H₂O₂ was metabolized by the catalatic reaction. Comparison of rates of O₂ evolution to estimated rates of H₂O₂ metabolism obtained by the methanol-titration method (H. Sies and B. Chance, 1970, FEBS Lett.11, 172–176) indicated that the contribution of the peroxidatic reaction of catalase was small. The intracellular activity of glutathione peroxidase was estimated as the catalase-independent metabolism and used to determine the rate of intracellular H₂O₂ metabolism by the peroxidase. The results provide a quantitative basis for analysis of the physiological and toxicological aspects of H₂O₂ metabolism by liver.