To clarify the role of free radicals and the efficacy of human superoxide dismutase (h-SOD) on cardiac ischemia/reperfusion injury, adult mongrel dogs were placed on a cardiopulmonary bypass (CPB). Aorta was cross clamped for 120 minutes and crystalloid cardioplegic solution was administered into the aortic root every 30 minutes. Sixteen dogs were divided into the control group and non cross clamped group (XCL(-)group). They were placed on total CPB for 130 minutes without an aortic cross clamp.
The control group showed higher thiobarbituric acid reactive substance (TBARS) release from heart in early reperfusion phase (P<0.05), and suppressed recovery of cardiac index (CI) and max dp/dt at 60 minutes after reperfusion (P<0.01 and P<0.05, respectively) than XCL (-) group. Eight dogs were administered saline and 32 dogs were administered saline and h-SOD into the aortic root just before reperfusion. Dogs, administered h-SOD, were devided into four groups by the dese of h-SOD, group I : 1mg/kg, group II : 3mg/kg, group III : 10mg/kg, and group IV : 20mg/kg. Between control and saline groups, no significant difference was found. Groups I and II showed suppressed TBARS release from the heart in the early reperfusion phase than the control group (P<0.01 and P<0.05, respectively). Groups II and III showed higher recovery of CI at 60 minutes after reperfusion than the control group (P<0.01 and P<0.05, respectively). In conclusion, significantly higher TBARS was released from the heart and recovery of cardiac function was suppressed in cardiac ischemia/reperfusion injury. The h-SOD administtation was effective to protect the heart from cardiac ischemia/reperfusion injury.