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The Role Of H 2 O 2 Generation In Perfused Rat Liver And The Reaction Of Catalase Compound I And Hydrogen Donors.
Published 1973 · Chemistry, Medicine
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Abstract 1. 1. Hydrogen peroxide production in hemoglobin-free perfused rat liver was measured quantitatively by analyzing the steady state level of catalase-H2O2 intermediate ( p m e ). The method is based on a relationship between the ratio of H2O2 generaztion rate ( dx n dt ) to catalase-heme concentration (e) and the concentration of methanol ( a 1 2 ) which causes a decrease in the p m e value to half of its saturation value ( p m e ). Endogenous hydrogen donor in the perfused liver was estimated to be equivalent to about 30 μ m methanol. 2. 2. The rate of H2O2 production in the perfused liver with 2 m ml -lactate and 0.3 m m pyruvate was 49 nmol/min/g wet wt liver at 30 °C. This rate corresponds to about 1.7% of the total liver respiration rate. 3. 3. Mitochondrial production of H2O2 was proved by the fact that fatty acids enhance the H2O2 production and that this enhancement was inhibited by either rotenone or antimycin A. Perfusion of antimycin A caused stimulation of H2O2 production by a factor of 1.7. In the presence of 0.3 m m octanoate, H2O2 generation increased to 170 nmol/min/g wet wt liver. The results strongly suggest that one of the major sources for H2O2 production is the mitochondrial system participating in fatty acid oxidation. 4. 4. Changes in the redox state of cytosolic pyridine nucleotides by xylitol or by lactate did not alter the H2O2 production signficantly. 5. 5. Peroxisomal H2O2 production was observed when the liver was perfused with either urate or glycolate. The maximum rate of H2O2 production in the presence of urate and glycolate were 750 and 490 nmol/min/g wet wt liver, respectively. 6. 6. The total role of H2O2 production and utilization is considered and H2O2 metabolism in the peroxisomes is compared with that of other systems. The general conclusion is that, the body regulates the intracellular H2O2 level below about 10−7 m , and with this level biological oxidations of considerable significance are possible through the catalase system.