The effect of superoxide dismutase in the myocardium during reperfusion in the dog.

The aim of the study was to investigate the pathological role of free radicals during myocardial reperfusion. Low (0.5 mg/kg body weight) and high doses (5 mg/kg) of superoxide dismutase (SOD) were infused into the left atrium of mongrel dogs for 4 min starting 29 min after ligation and 1 min before reperfusion of the left anterior descending coronary artery (LAD). Arterial blood pressure, heart rate, electrocardiogram, and the regional contractile force of the left ventricle were monitored throughout the ligation (30 min) and reperfusion periods (20 min). Concentrations of creatine kinase (CK) and malondialdehyde (MDA) in the coronary sinus blood were determined before (0 min) and during ligation (15 and 25 min) and during reperfusion of the LAD (2, 7, and 20 min). In other groups of dogs, the effect of the two doses of SOD on epicardial blood flow was investigated during ligation and reperfusion by the measurement of epicardial temperature using a thermocardiograph. Experimental subjects were mongrel dogs of either sex (n = 25), weight 10-35 kg. Compared to controls (mean +/- SEM, 43.1 +/- 1.2; n = 7), the number of ventricular extrasystoles during the first 5 min of reperfusion was significantly (p < .001) decreased in dogs treated with the high dose (15.01 +/- 2.14; n = 5), but not in those receiving the low dose of the drug (34.6 +/- 5.66; n = 5). The concentrations of CK increased gradually until the end of reperfusion without differences among the different groups. Plasma MDA was the highest in control dogs 7 min after reperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)