GENERATION OF SUPEROXIDE RADICALS BY MITOCHONDRIAL RESPIRATORY-CHAIN IN ISOLATED CARDIAC MYOCYTES

Electron spin resonance was used to investigate the generation of supe roxide radicals by the mitochondrial respiratory chain of isolated sap onin-treated rat cardiac myocytes. The hydroxylamine TEMPONE-H was use d as a spin trap. A device was designed for constant mixing of the sam ple in the ESR resonator to prevent aggregation of the cardiac myocyte s. The rate of generation of superoxide radicals increased on adding s ubstrates and the inhibitors of the mitochondrial respiratory chain ro tenone and antimycin A; the maximal stimulatory effect was observed in the presence of both inhibitors. The addition of superoxide dismutase and KCN suppressed the generation of superoxide radicals, indicating that this process occurred in the complex bc(1) of the mitochondrial r espiratory chain. The ratios between the rates of generation of supero xide radicals under various conditions are in good agreement with data obtained from earlier experiments with isolated mitochondria. However , the absolute rates observed in cardiac myocytes were approximately 2 -fold higher that those measured in isolated mitochondria, probably be cause some mitochondria had been damaged by the isolation procedures.