It has been suggested that the beneficial effects of reperfusing ischemic myocardium might be in part reversed by the occurrence of "
reperfusion injury." One possible mechanism could be the generation of
oxygen free radicals.
Superoxide dismutase enzymatically scavenges
superoxide radicals by dismutation to
hydrogen peroxide. This study tested the hypothesis that administration of recombinant human
superoxide dismutase (h-SOD) at the time of reflow after a period of prolonged global
ischemia would result in improved recovery of myocardial metabolism and function by preventing or reducing a potentially harmful component of reperfusion. We also sought to determine whether
catalase, an enzymatic scavenger of
hydrogen peroxide, was a necessary addition for optimal benefit. Langendorff perfused rabbit hearts were subjected to 30 min of normothermic (37 degrees C) total global
ischemia. At the moment of reperfusion, 12 control hearts received
a 10 ml bolus of normal perfusate followed by 15 min of reperfusion with normal perfusate (group I), 12 hearts received 60,000 IU of h-SOD as a bolus followed by a continuous infusion of 100 IU/ml for 15 min (group II), and 12 hearts received 60,000 IU of h-SOD and 60,000 IU of
catalase as a bolus followed by 100 IU/ml of both
enzymes for 15 min (group III). Myocardial
ATP and
phosphocreatine (PCr) content and intracellular pH during
ischemia and reperfusion were continuously monitored with 31P nuclear magnetic resonance (NMR) spectroscopy. During 30 min of normothermic global
ischemia intracellular pH dropped from 7.11-7.18 to 5.58-5.80 in all three groups of hearts. Likewise myocardial PCr content fell rapidly to 7% to 8% and
ATP fell more slowly to 29% to 36% of preischemic control content. After 45 min of reperfusion PCr recovered to 65 +/- 5% of control in untreated (group I) hearts compared with 89 +/- 8% in h-SOD-treated (group II) hearts (p less than .01 vs group I) and with 83 +/- 6% of control in h-SOD/
catalase-treated (group III) hearts (p less than .05 vs group I). Recovery of isovolumic left ventricular developed pressure was 68 +/- 5% of control in h-SOD-treated (group II) hearts and 66 +/- 6% of control in h-SOD/
catalase-treated (group III) hearts after 45 min of reflow, compared with 48 +/- 6% of control in untreated (group I) hearts (p less than .005 for groups II and III vs group I). The NMR data confirmed equal depletion of
ATP and PCr content in all three groups of hearts.(ABSTRACT TRUNCATED AT 400 WORDS)