Monoamine Oxidase Activity of Mitochondria Prepared from Rat Liver and Rat Heart

The effect of agents that change the respiratory state of the mitochondrion on tyramine oxidation was investigated. Neither uncoupler nor ADP and P1 in the presence of substrate produced any change in the rate of tyramine oxidation, as judged by direct measurement of tyramine oxidation or by H2O2 production. We conclude that previously reported depression of monoamine oxidase activity by stimulated respiration was due to oxygen depletion.