Li X Y, McCay P B, Zughaib M, Jeroudi M O, Triana J F, Bolli R
Department of Medicine, Baylor College of Medicine, Houston, Texas 77030.
J Clin Invest. 1993 Aug;92(2):1025-41. doi: 10.1172/JCI116608.
Conscious dogs undergoing a 15-min coronary occlusion were given alpha-phenyl N-tert-butyl nitrone (PBN) and the local coronary venous plasma was analyzed by electron paramagnetic resonance spectroscopy. A prolonged myocardial release of PBN radical adducts was observed, which exhibited a burst in the initial minutes of reflow (peaking at 3 min) and then abated but continued for 1-3 h after reperfusion. Computer simulation revealed the presence of at least two PBN adducts (aN = 15.2 G and a beta H = 6.0 G; aN = 14.6 G and a beta H = 3.0 G), both consistent with the trapping of secondary carbon-centered radicals. No appreciable PBN adduct production was observed when collateral flow exceeded 30-40% of nonischemic flow, indicating that a flow reduction of at least 60% is necessary to trigger free radical reactions. There was a direct relationship between the magnitude of PBN adduct production and the severity of contractile dysfunction (r = 0.77), suggesting that the radicals generated upon reperfusion play a causal role in the subsequent stunning. The total release of PBN adducts after 3 h of reperfusion following a 15-min coronary occlusion was found to be approximately five times greater in open-chest compared with conscious dogs; at the same time, the recovery of wall thickening was markedly less in open-chest dogs. This study represents the first application of spin trapping to a conscious animal model of myocardial ischemia. The results demonstrate (a) that free radicals are generated in the stunned myocardium in the absence of the artificial or abnormal conditions associated with previously used models (isolated hearts, open-chest preparations), and (b) that both the severity of postischemic dysfunction and the magnitude of the attendant free radical production are greatly exaggerated in the open-chest dog, implying that previous conclusions derived from this model may not be applicable to conscious animals or to humans. This investigation also provides a method to measure free radicals in awake animals.
对清醒状态下的犬进行15分钟冠状动脉闭塞处理后，给予α-苯基N-叔丁基硝酮（PBN），并通过电子顺磁共振波谱分析局部冠状静脉血浆。观察到PBN自由基加合物在心肌中的释放持续时间延长，在再灌注的最初几分钟出现爆发（3分钟时达到峰值），然后减弱，但在再灌注后持续1 - 3小时。计算机模拟显示存在至少两种PBN加合物（aN = 15.2 G，βH = 6.0 G；aN = 14.6 G，βH = 3.0 G），两者均与仲碳中心自由基的捕获一致。当侧支血流超过非缺血血流的30 - 40%时，未观察到明显的PBN加合物生成，表明至少60%的血流减少是触发自由基反应所必需的。PBN加合物生成量与收缩功能障碍的严重程度之间存在直接关系（r = 0.77），提示再灌注时产生的自由基在随后的心肌顿抑中起因果作用。发现冠状动脉闭塞15分钟后再灌注3小时，开胸犬的PBN加合物总释放量比清醒犬大约高五倍；与此同时，开胸犬的室壁增厚恢复明显较差。本研究首次将自旋捕获技术应用于清醒动物心肌缺血模型。结果表明：（a）在没有与先前使用的模型（离体心脏、开胸制备）相关的人工或异常条件下，心肌顿抑中会产生自由基；（b）开胸犬缺血后功能障碍的严重程度和伴随的自由基生成量都被大大夸大，这意味着从该模型得出的先前结论可能不适用于清醒动物或人类。本研究还提供了一种测量清醒动物体内自由基的方法。
