The Clarification of Mechanisms for Electron Transfer and Identification of Radicals in Myocardium

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This study indirectly showed the involvement of oxygen derived free radicals (O_2-FR) in reperfusion injury by the myocardial protection of radical scavengers and directly demonstrated free radicals in the frozem myocardium using electron spin resonance (ESR) spectroscopy.In 19 open chest dogs, the left anterior descending coronary artery was occluded for 90 min and subsequently reperfused for 60 min. The severity of myocardial injury was evaluated by ratios of necrotic to perfused areas determined by dual fluorescence methods. Dogs treated with SOD, catalase and mannitol disclosed significantly limited necrosis than that in control (34.1 12.0 vs. 66.0 11.3%); indirectly veraifying that the O_2-FR play an important role in the genesis of ischemia/reperfusion injury.For direct proof of free radical hypothesis, radicals in the frozen myocardium were measured using electron spin resonance spectroscopy (ESR). The ESR spectra exhibited four radicals, however, two radicals which had been previously claimed as O_2-FR and N-centered radical by other investigators were shown as mechanically yielded artifactual radicals. In artifact-free samples, O_2-FR could not be detected. One radical native to the myocardium was identified as coenzyme Q_<10> radical which might provide an index of severity of reperfusion injury. Spin trapping method with ESR can be an optimal method for the direct measurement of oxygen derived radicals.