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Spaciotemporal Alteration of 8-hydroxy-2′-deoxyguanosine Levels in Cardiomyocytes After Myocardial Infarction in Rats

Temporary or persistent heart failure is one of the major complications after myocardial infarction (MI). In order to elucidate the pathogenesis of MI, we studied the spaciotemporal alteration of 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels in cardiomyocytes in a rat model of ligation of the left anterior descending branch of the coronary artery. The lethality in this model was 18%. Hearts were dissected at 0, 3, 6, 12, 24, 48 h, and 1, 2, 4, 6 weeks after the operation. The cardiac level of 8-OHdG was evaluated biochemically as well as by immunohistochemistry with monoclonal antibody N45.1. Three to 6 h after ligation, the 8-OHdG levels were increased in the cardiomyocytes of MI (six-fold) and peri-MI (four-fold) areas. After 24 h, the myocardium in the MI area was necrotized, and thereafter the 8-OHdG level decreased. 8-OHdG levels in the myocardium of peri-MI areas returned once to a normal level, but were significantly increased at 2-4 weeks along with the appearance of apoptotic cardiomyocytes in this area. The heart after MI has been generally considered as clinically stable after four weeks. However, cardiomyocytes near the infarcted area were oxidatively stressed even after four weeks when the affected lesion was extensive. The present data support the use of supplementary antioxidant therapies to save functional myocardium after MI. (213 words)