Tang X L, Qiu Y, Turrens J F, Sun J Z, Bolli R
Department of Medicine, Baylor College of Medicine, Houston, Texas 77030, USA.
Am J Physiol. 1997 Oct;273(4):H1651-7. doi: 10.1152/ajpheart.1997.273.4.H1651.
Previous studies in conscious pigs have demonstrated that a sequence of ten 2-min coronary occlusion/2-min reperfusion cycles renders the heart relatively resistant to myocardial stunning 24 h later [late preconditioning (PC) against stunning] by an unknown mechanism. Since oxygen radicals contribute importantly to myocardial stunning and since antioxidant enzymes have been reported to be upregulated 24 h after PC in dogs and rabbits, we tested the hypothesis that late PC against stunning is related to an increase in endogenous antioxidant defenses. Chronically instrumented conscious pigs underwent a sequence of ten 2-min coronary occlusion/2-min reperfusion cycles (preconditioned group, n = 11) or received no intervention (control group, n = 5). Twenty-four hours later, pigs were killed and the myocardial levels of Mn superoxide dismutase (SOD), Cu-Zn SOD, catalase, glutathione (GSH) peroxidase, GSH reductase, GSH, GSH disulfide, alpha-tocopherol, and ascorbate were measured. There were no differences in any of the enzymatic or nonenzymatic antioxidants between the ischemic and nonischemic regions in the preconditioned group or between the control and the preconditioned group. Thus, when a marked protection against stunning was present (24 h after PC), no alteration in antioxidant defenses was observed. These results indicate that, in conscious pigs, late PC against myocardial stunning is not mediated by increased endogenous antioxidant defenses, thereby refuting one of the major current hypotheses regarding this phenomenon.
先前对清醒猪的研究表明，一系列十个2分钟冠状动脉闭塞/2分钟再灌注周期会使心脏在24小时后对心肌顿抑具有相对抗性[晚期预处理（PC）抗顿抑]，其机制不明。由于氧自由基对心肌顿抑起重要作用，且有报道称在犬和兔中PC后24小时抗氧化酶会上调，我们检验了晚期PC抗顿抑与内源性抗氧化防御增加有关的假说。长期植入仪器的清醒猪接受一系列十个2分钟冠状动脉闭塞/2分钟再灌注周期（预处理组，n = 11）或不接受任何干预（对照组，n = 5）。24小时后，处死猪并测量心肌中锰超氧化物歧化酶（SOD）、铜锌SOD、过氧化氢酶、谷胱甘肽（GSH）过氧化物酶、GSH还原酶、GSH、GSH二硫化物、α-生育酚和抗坏血酸的水平。预处理组的缺血区和非缺血区之间或对照组与预处理组之间，任何酶促或非酶促抗氧化剂均无差异。因此，当存在明显的抗顿抑保护作用时（PC后24小时），未观察到抗氧化防御的改变。这些结果表明，在清醒猪中，晚期PC抗心肌顿抑不是由内源性抗氧化防御增加介导的，从而驳斥了目前关于这一现象的主要假说之一。
