Superoxide dismutase and catalase do not improve recovery of regional myocardial contractile function when given at the time of reperfusion after reversible regional ischemia in anesthetized dogs

Earlier studies have demonstrated an improvement in the recovery of the regional myocardial function after reversible myocardial ischemia when dogs were treated with superoxide dismutase (SOD) + catalase (CAT). In all these studies, drug administration was started prior to the ischemic period. The aim of this study was to investigate the effects of SOD and CAT on the recovery of the regional contractile function in anesthetized beagle dogs when the drugs were administered at the time of reperfusion. The animals were subjected to 20 min of left coronary artery occlusion followed by 3 h reperfusion. The regional myocardial contractile function, measured as subendocardial segment shortening (SS, sonomicrometry) decreased to below zero and the regional blood flow in the ischemic subendocardium was reduced to about 5% of pre-ischemic values during the coronary artery occlusion period. The size of the occluded bed was similar in the two groups. Saline (n = 8) or SOD (10 mg/kg) + CAT (3.4 mg/kg) (n = 8) were infused into the left atrium from 2.5 min prior to until 20 min after the start of reperfusion. The peak plasma level of SOD was 102 +/- 15 mg/l at 20 min reperfusion. There were no significant differences in the arterial blood pressure, cardiac contractile function and regional blood flow between the two groups at any time during the experiment. During reperfusion in the dogs given vehicle, SS recovered to 48 +/- 7% (mean +/- SEM) after the first hour of reperfusion, and to 51 +/- 6% of pre-ischemic values after 3 h of reperfusion.