Free Radicals and Metabolic State of the Reperfused Myocardium

氧源性自由基最近被认为是引起心肌缺血和再灌注损伤的重要因素。然而，没有合适的技术来直接测量这些自由基的产生，因为氧衍生的自由基非常活跃，寿命很短。本研究的目的是：1)利用电子自旋共振（ESR）光谱直接评价心肌中氧源性自由基的含量；2)评价再灌注损伤心肌中自由基清除剂的含量；3)研究再灌注犬心脏中自由基清除剂的作用；4)研究再灌注心肌中能量水平和pH值与血管损伤严重程度的关系。结果:(1)取20只开胸犬心脏和离体逆行灌注的大鼠心脏，在再灌注后立即用预冷钳冷冻夹住心肌，用电子波谱（ESR）在-196℃下测定样品中的自由基含量。冷冻夹住法可能由于检测范围较低而无法显示O_2-，但已证实心肌中存在辅酶Q_<10>自由基。2)利用犬心脏，测定缺血3小时或缺血90分钟后再灌注心肌的SOD活性。SOD活性为21 ~ 22单位/mg prot，与正常心肌保持相同水平。3) 20只开胸犬，经LAD闭塞后心脏缺血90 min，再灌注60 min。超氧化物歧化酶（15000 U/kg）组的心功能及坏死面积等各项指标损伤均小于无超氧化物歧化酶组。4)用^<31 b> P-NMR谱监测25只灌注心脏缺血再灌注时心肌高能磷酸盐和pH值。心肌中辅酶Q_<10>自由基是组织氧化还原状态的一个指标，在心脏中表现出不均匀的pH和低ATP水平。少

Oxygen-derived radicals have recently been implicated as important agents in causing tissue damage in myocardial ischemia and reperfusion injury. However, there is no appropriate technique for the direct measurement of the generation of these radicals, since oxygen-derived radicals are extremely reactive and have short life spans. The purposes of this study are 1) to directly evaluate oxygen derived radicals in myocardium using electron spin resonance (ESR) spectroscopy, 2) to evaluate radical scavenger contents of the myocardium subjected to reperfusion injury 3) to show the efficacy of radical scavengers in reperfused canine hearts, and 4) to correlate the energy levels and pH in the reperfused myocardium to the severity of vascular impairment.RESULTS: 1) Using 20 open chest canine hearts and isolated retro-perfused rat hearts the myocardium was freeze-clamped with precooled tongs immediately after reperfusion and free radicals existing in the samples were measured using electron spi … More n resonance spectroscopy (ESR) at -196 C. The freeze-trapping method failed of demonstrating O_2- probably due to low detection range of this method, however, the presence of coenzyme Q_<10> radical in the myocardium has been demonstrated. 2) Using canine hearts, SOD activities in myocardium rendered ischemia for 3 hours or reperfused after 90 min of ischemia were evaluated. SOD activities revealed 21-22 units/mg prot which remained in the same range of that in normal myocardium. 3) In 20 open chest dogs, hearts were subjected to a 90 min period of ischemia by LAD occlusion followed by 60 min reperfusion. In the group which received SOD (15000 U/kg) demonstrated less injury than the group without SOD in all parameters of cardiac functions and area of necrosis. 4) In 25, perfused hearts, myocardial high energy phosphate and pH were monitored by ^<31>P-NMR spectra during ischemia and reperfusion. Coenzyme Q_<10> radical in myocardium, an indicator of tissue redox state, was low in hearts which demonstrated heterogeneous pH and low ATP levels. Less