Flap Necrosis as an Ischemia-Reperfusion Injury Model and its Pharmacological Control

在许多缺血性疾病和器官移植中观察到的缺血/再灌注损伤伴随着活性氧自由基(ROS)的形成。本研究的目的是利用合适的皮瓣模型探讨这类损伤的机制和预防。在缺血期间，ATP被分解为次黄嘌呤，黄嘌呤氧化酶的底物，黄嘌呤脱氢酶被钙激活的中性蛋白水解酶转化为氧化酶。当组织被复氧时，会产生大量的超氧化物和过氧化氢，从而导致组织损伤。取大鼠岛状和随机两种皮瓣，分别注射脂质体超氧化物歧化酶(L-超氧化物歧化酶)、E--c(钙蛋白酶等半胱氨酸蛋白酶的特异性抑制剂)或别嘌醇(黄嘌呤氧化酶抑制剂)后，测定血流量、皮肤超氧化物歧化酶活性和成活率。三种药物均可提高岛状皮瓣结扎10小时后的存活率。血流量和超氧化物歧化酶活性明显降低。然而，只有L-超氧化物歧化酶，而不是E--c或别嘌醇，可以延长随机皮瓣的存活时间。这些结果提示黄嘌呤氧化酶系统产生的ROS在缺血/再灌流损伤中起重要作用。此外，使用三种药物的不同结果表明，在这两种模型中，可能涉及不同的机制与中性粒细胞依赖的炎症有关。我们的简单和定量的皮瓣模型在药理学评估和筛选任何可能的治疗缺血性心脑血管疾病的药物以及器官移植方面都是有用的。

Ischemia/reperfusion injury observed in many ischemic diseases and organ transplantation is accompanied by the formation of reactive oxygen species (ROS). The purpose of the present study is to investigate the mechanism and prevention of this type injury using suitable skin flap models. During ischemia, ATP is broken down to hypoxanthine, a substrate of xanthine oxidase, and xanthine dehydrogenase is converted to oxidase by calpain, a calcium activated neutral proteinase. When the tissue is reoxygenated, a burst of superoxide and hydrogen peroxide occurs with resultant tissue damage. Two kinds of skin flaps, island and random, were lifted in rats, and the blood flow, cutaneous superoxide dismutase (SOD) activity, survival rates were measured after injection of liposomal SOD (L-SOD), E-64-c (specific inhibitor of cysteine proteinases including calpain) or allopurinol (xanthine oxidase inhibitor). Improved survival of island skin flaps after 10hr ligation was observed by these three agents. Remarkably reduced blood flow and SOD activity were confirmed. However, only L-SOD, but not E-64-c or allopurinol, improved the survival length in random skin flaps. These findings suggest the significant contribution of ROS generated in xanthine oxidase system to ischemia/reperfusionn injury. Also the discrepant results using three agents indicate the involvement of different mechanisms presumably linking to neutrophil-dependent inflammation in these two models. Our simple and quantitati ve skin flap models are useful in pharmacological evaluation and screening of any possible agent for the treatment of ischemic heart and cerebrovascular diseases as well as organ transplantation.