Role of oxygen free radicals in reperfusion myocardial injury

为了确定再灌注缺血心肌中氧自由基的产生与心肌损伤进展之间的关系，我们在犬冠状动脉闭塞（90分钟）-再灌注模型中测量了缺血心肌中氧自由基的产生和扩展的梗死面积。我们采用电子顺磁共振（EPR）自旋捕获技术（5,5'-二甲基-吡咯啉-氧化物，DMPO）检测针活检快速冷冻心肌样品中的氧自由基。再灌注前后正常心肌均未检测到DMPO加合物的生成。在缺血再灌注心肌中，检测DMPO-OOH（超氧阴离子）和DMPO-OH（羟基自由基）的EPR信号，DMPO-OOH和DMPO-OH分别在再灌注后1小时和3小时达到峰值。这些DMPO加合物在再灌注早期（15秒）也能检测到，但其浓度明显低于再灌注后期。在实验过程中，人重组超氧化物歧化酶（2.5 mg/kg/h）和过氧化氢酶（2.5 mg/kg/h）处理可消除dpo - ooh的形成，但对dpo - oh的形成影响不大。栓塞90分钟时，使用Evans蓝染料和三苯四唑氯双染色法定量的梗死面积（梗死危险区域的百分比）为18.3 <正负> 4.8%（平均<正负> SEM）。再灌注后，再灌注5小时梗死面积增加至43.6 <±bb0 7.2%。这些结果表明，缺血心肌组织在再灌注后期（1-3小时）持续产生更大程度的氧自由基，与心肌梗死的进展有关。氧自由基与进行性梗死的同时出现可能支持氧自由基连锁反应有助于缺血后心肌细胞损伤的传播的观点

To define the relationship between oxygen-derived free radical (oxy-radical) generation in the reperfused ischemic myocardium and the progression of myocardial damage, we measured oxy-radical generation in the ischemic myocardium and the propagating infarct size in a canine coronary occlusion (90 minutes)-reperfusion model. We used electron paramagnetic resonance (EPR) spin trapping techniques (5,5'-dimethyl-l-pyrroline-n-oxide, DMPO) to detect oxy-radicals in the rapidly frozen myocardial samples taken by needle biopsy. There was no detectable generation of DMPO adducts in the normal myocardium before and after reperfusion. In the reperfused ischemic myocardium, EPR signals of DMPO-OOH (superoxide anion) and DMPO-OH (hydroxyl radical) were detected, with peak concentrations at 1 hour after reperfusion for DMPO-OOH and at 3 hours after reperfusion for DMPO-OH, respectively. These DMPO adducts were also detected during the early phase (15 seconds) of reperfusion, but the concentrations … More of these signals were much less than those during the late phase of reperfusion.Treatment with human recombinant superoxide dismutase (2.5 mg/kg/hour) and catalase (2.5 mg/kg/hour) during the course of the experiments abolished DLIPO-OOH formation but had little effect on DMPO-OH formation. Infarct size (percent of risk area infarcted), quantified by a dual staining method using Evans blue dye and triphenyltetrazolium chloride, was 18.3 <plus-minus> 4.8% (mean <plus-minus> SEM) at 90 minutes of occlusion. After reperfusion, infarct size increased to 43.6 <plus-minus> 7.2% at 5 hours of reperfusion. These results indicate that a greater magnitude of oxy-radical generation was sustained in the ischemic myocardial tissue during the late phase (1-3 hours) of reperfusion, associated with the progression of myocardial infarction. The concurrent appearance of oxy-radicals and progressive infarction may support the view that a chain reaction of oxy-radicals contributes to the propagation of myocardial cell damage in the postischemic Less