Zweier J L
Department of Medicine, Johns Hopkins Medical Institutions, Baltimore, Maryland 21224.
J Biol Chem. 1988 Jan 25;263(3):1353-7.
There has been considerable controversy regarding the role of oxygen free radicals as important mediators of cell damage in reperfused myocardium. This controversy regards whether superoxide and hydroxyl free radicals are generated on reperfusion and if these radicals actually cause impaired contractile function. In this study, EPR studies using the spin trap 5,5-dimethyl-1-pyroline-n-oxide (DMPO) demonstrate the formation of .OH and R. free radicals in the reperfused heart. EPR signals of DMPO-OH, aN = aH = 14.9 G, and DMPO-R aN = 15.8 G aH = 22.8 G are observed, with peak concentrations during the first minute of reperfusion. It is demonstrated that these radicals are derived from .O2- since reperfusion in the presence of enzymatically active recombinant human superoxide dismutase markedly reduced the formation of these signals while inactive recombinant human superoxide dismutase had no effect. On reperfusion with perfusate pretreated to remove adventitial iron, the concentration of the DMPO-OH signal was increased 2-fold and a 4-fold decrease in the DMPO-R signal was observed demonstrating that iron-mediated Fenton chemistry occurs. Hearts reperfused with recombinant human superoxide dismutase exhibited improved contractile function in parallel with the marked reduction in measured free radicals. In order to determine if the reperfusion free radical burst results in impaired contractile function, simultaneous measurements of free radical generation and contractile function were performed. A direct relationship between free radical generation and subsequent impaired contractile function was observed. These studies suggest that superoxide derived .OH and R. free radicals are generated in the reperfused heart via Fenton chemistry. These radicals appear to be key mediators of myocardial reperfusion injury.
关于氧自由基作为再灌注心肌细胞损伤的重要介质所起的作用，一直存在着相当大的争议。这场争议涉及到再灌注时是否会产生超氧阴离子和羟基自由基，以及这些自由基是否真的会导致收缩功能受损。在本研究中，使用自旋捕获剂5,5 - 二甲基 - 1 - 吡咯啉 - N - 氧化物（DMPO）的电子顺磁共振（EPR）研究表明，再灌注心脏中会形成·OH和R·自由基。观察到DMPO - OH的EPR信号，aN = aH = 14.9 G，以及DMPO - R的EPR信号，aN = 15.8 G，aH = 22.8 G，在再灌注的第一分钟达到峰值浓度。结果表明，这些自由基源自·O2-，因为在有酶活性的重组人超氧化物歧化酶存在的情况下进行再灌注，显著降低了这些信号的形成，而无活性的重组人超氧化物歧化酶则没有影响。在用经过预处理以去除外膜铁的灌注液进行再灌注时，DMPO - OH信号的浓度增加了2倍，同时观察到DMPO - R信号降低了4倍，这表明发生了铁介导的芬顿化学反应。用重组人超氧化物歧化酶进行再灌注的心脏，其收缩功能得到改善，同时测量到的自由基显著减少。为了确定再灌注自由基爆发是否会导致收缩功能受损，同时进行了自由基生成和收缩功能的测量。观察到自由基生成与随后的收缩功能受损之间存在直接关系。这些研究表明，再灌注心脏中通过芬顿化学反应产生了源自超氧阴离子的·OH和R·自由基。这些自由基似乎是心肌再灌注损伤的关键介质。
