BRIEF MYOCARDIAL-ISCHEMIA AFFECTS FREE-RADICAL GENERATING AND SCAVENGING SYSTEMS IN DOGS

This study examined whether brief repeated myocardial ischemia altered free radical generating and scavenging activity in a dog model. In do gs preconditioned with four 5-min left anterior descending coronary ar tery (LAD) occlusions and reperfusions, we examined transcardiac chang es in both the function of neutrophils, cells which are major free rad ical generators, and in myocardial antioxidant enzyme activity, as an indication of free radical scavenging. Neutrophil function was assesse d by determining luminol-enhanced whole blood chemiluminescence (CL) i nduced by zymosan. Blood was taken simultaneously from the carotid art ery and the cardiac vein running along the occluded LAD. Preconditioni ng with sublethal ischemia significantly reduced whole blood CL in the cardiac vein compared with the carotid artery after the first and fou rth 5-min reperfusions, while there was no difference in neutrophil co unt between these sampling sites. Immediately after brief repeated isc hemia and reperfusion, manganese-superoxide dismutase (SOD) activity w as significantly enhanced, and glutathione reductase activity was mark edly reduced in the ischemic, compared with the non-ischemic, myocardi um. There were no differences in the myocardial activities of copper, zinc-SOD, glutathione peroxidase, and glutathione S-transferase betwee n the ischemic and non-ischemic regions. Also, no difference was obser ved between the reduced myocardial glutathione levels in these regions , although the oxidized glutathione level was significantly higher in the ischemic regions of the subepicardial and sub-endocardial areas. W e demonstrated that brief repeated ischemia affects free radical gener ating and scavenging systems in the ischemic myocardium.