【作者】 李芳芳；

【导师】 厉有名；

【作者基本信息】 浙江大学 ， 内科学， 2004， 硕士

【摘要】 目的和背景 随着人民生活水平的提高，脂肪性肝病的发病率越来越高。酒精摄入、肥胖、营养不良、药物毒性、高脂血症、代谢或内分泌失调(如糖尿病)等是肝脏发生脂肪变的高危因素。据不完全统计，在常规显微镜下检查，发现约有30％的供肝有不同程度的脂肪变，约有10％的供肝因有中、重度脂肪变而不能用作供肝进行移植，在肝脏手术中也有近20％的患者是脂肪肝。在肝脏手术(肝移植、肝叶切除术)中，常需阻断肝脏血流造成缺血再灌注损伤，容易导致术后肝功能衰竭，影响手术疗效及移植物的存活。许多研究证明存在脂肪变的肝脏比正常肝脏对缺血再灌注损伤的耐受性差。有报道在脂肪肝患者肝叶切除术中夹闭血管60min，术后出现肝功能衰竭。接受具有中、重度脂肪变的供肝会降低移植物和病人的存活率。另外，供肝脂肪变是移植后移植物发生原发性肝无能(primary non-function，PNF)或最初肝功能衰竭(initial poor function，IPF)的高危因素。目前对脂肪肝缺血再灌注(ischemia reperfusion，I／R)损伤的研究较多，但其具体的损伤机制尚不十分清楚，许多假说试着阐述脂肪肝对缺血再灌注损伤的耐受性降低的原因，具体包括：(1)脂质过氧化增加，脂质负荷过重的肝细胞的抗氧化能力下降。(2)中性粒细胞浸润增加。(3)微循环的损害。(4)Kupffer细胞的激活及炎性介质的释放：如：TNF-α等。 早在1986年Murry在研究心肌缺血时提出了缺血预处理的概念，短暂的缺血并不产生代谢产物的堆积，也不会造成高能磷酸储备减少，但能通过某种机 浙江大学硕士学位论文制启动内源性的保护机制，从而减轻随后而来的较长时间的缺血再灌注损害。缺血预处理(isehemie preeonditioning，IpC)是缺血损伤强有力的保护机制，己经证明这种保护作用不仅存在于心脏，对许多脏器均有保护作用，如:大脑、脊髓、视网膜、肝脏、肺及骨骼肌等。许多研究证明缺血预处理对正常肝脏的缺血再灌注损伤具有保护作用，表现为:明显降低缺血再灌注后的肝细胞坏死和凋亡，减轻肝脏损害标记酶的变化;降低窦状内皮细胞的损害，改善微循环失衡，减轻白细胞、血小板与肝窦内皮细胞的豁附;增加肝脏细胞的胆汁分泌;减轻肝细胞内酸中毒和钠超载;抑制Kupffer细胞的激活，减少翎F一。、IL一1等炎性因子的释放;降低肝脏及各脏器的中性粒细胞浸润及氧自由基的产生;增加剩余肝细胞活性和肝组织ATP含量;增加肝脏血流;提高实验动物的存活力。 Anna Serafin等人研究发现缺血预处理能提高Zucker肥胖大鼠脂肪肝对缺血再灌注损伤的耐受性。缺血预处理是否也能提高高脂饮食致大鼠脂肪肝对缺血再灌注损伤的耐受性?目前的研究甚少。本实验通过高脂饮食喂养建立SD大鼠脂肪肝模型，用苏丹m染色观察肝脏脂肪蓄积情况，HE染色观察基本病理变化，用化学比色法检测血清酶学指标、肝组织匀浆的氧化及抗氧化指标。探讨缺血预处理是否能提高高脂饮食致大鼠脂肪肝对缺血再灌注损伤的耐受性及其潜在机制。材料与方法 动物分组及处理:清洁级SD雄性大鼠72只，体重约140一1609。随机分成8组，l一4组为高脂饮食组大鼠，1组为对照组、2组为缺血再灌注组(1瓜)、3组为smin缺血预处理组(IPC一5)及4组为10min缺血预处理组(IPC一10)，以高脂饲料喂养，高脂饲料配方如下:2%胆固醇+lO%猪油+88%普通饲料;5一8组为普通饮食组大鼠，5组为对照组、6组为1/R组、7组为IPC一5组、8组为IPC一10组，予以普通饲料喂养。所有大鼠均自由采食、自由饮水;动物房通风良好、室温20一22度，昼夜周期12小时。大鼠每周称重一次，至4w末进行手术处理。 手术方案:2%戊巴比妥钠(30一40m叭g)腹腔内注射。腹部正中切口，分离左、中、右肝蒂，无损伤血管夹阻断左、中肝蒂血流，造成肝脏70%的缺 浙江大学硕士学位论文血，松开血管夹造成再灌注。1瓜组大鼠分别缺血40min，再灌注gomin;IPC一5组大鼠分别先阻断smin、再灌注smin后同呱组;IPC一10组大鼠先阻断smin、再灌注10min后同1瓜组;对照组仅腹部正中切口及分离肝蒂。手术结束后腹主动脉取血及留取缺血部分的肝组织。 HE染色观察肝脏基本病理学改变;苏丹m染色观察肝脏脂肪蓄积情况。检测血清丙氨酸氨基转移酶(alanine aminotransferase，ALT)、天冬氨酸氨基转移酶(aspartate aminotransferase，AsT)，乳酸脱氢酶(lactate dehydrogenase LDH)、一氧化氮(nitrie oxide，No)及肝组织超氧化物歧化酶(s即eroxide dismutase，Son)、丙二醛(malondialdehyde，MnA)、谷肤甘肤(glutathione，GsH)及髓过氧化物酶(明eloperoxidase，MPo)水平。 统计学处理:各指标测定数据均以均值士标准差表示，采用SPSS 10.0软件包分析处理。采用方差检验，组间比较采用SNK检验;方差不齐时采用非参数检验。p<0.05为统计学上差别具有显著性意义，p<0.01为差别有非常显著性意义。结果 一、一般状态观察:正常组大鼠毛色亮泽，活泼，食欲佳，无消瘦、搪便等。更多还原

【Abstract】 Backgrounds and PurposesThe ischemia-reperfusion(I/R) injury is an important cause of liver damage during surgical procedures including hepatic resections and liver transplantation. Liver steatosis is popular among people, affecting about 25% of donors for liver transplantation and 20% of patients undergoing liver resection. It can be caused by obesity, ethanol toxicity, or variety of metabolic disorders(such as diabetes mellitus, hyperlipemia). Hepatic steatosis is a major risk factor after liver surgery because steatotic livers tolerate poorly to I/R injury. Fatty livers are extremely sensitive to the deleterious effects of ischemia-reperfusion injury. The occurrence of postoperative liver failure after hepatic resection in a steatotic liver exposed to 60 min of vascular clamping has been reported. Moreover, fatty infiltration of a donor liver is a well-known risk factor for the development of graft dysfunction and in some cases graft failure after transplantation. However, the precise mechanism underlying increased vulnerability of fatty livers to I/Rinjury is still not fully understood. Current opinions suggest that the enhanced I/Rinjury IN fatty livers may be attributed to 1) fat solidification during organ preservation and hepatocyte disruption during reperfusion;2) enhanced lipid peroxidation; 3) increased damage to the sinusoidal microcirculation and increased leukocyte adhesion to the sinusoidal endothelial cells; 4) increased Kupffer cell activation; 5) deterioration of mitochondria ATP synthesis; and 6) decreased antioxidant defenses of the fat-laden hepatocytes. In 1986, Murry et al. discovered that a short period of ischemia and reperfusion led to an unexpected resistance of myocardium to a subsequent prolonged ischemia. The phenomenon, called ischemia preconditioning (IPC), has been subsequently documented in several organs, including cerebrum, spinal cord, optomein , Skeletal muscles , liver and lung.IPC is a potential therapeutic strategy, which may increase the tolerance of normal liver to ischemia-reperfusion injury demonstrated in animals as well as humans. But the mechanism of the preconditioning effect in the liver remains uncertain. Current thinking suggests that the protective effect may be attributed to 1) depresses Cellular necrosis and apoptosis; 2) protects the sinusoidal endothelial cells, improves liver microcirculation and decreases leucocytes adhere to platelet and endothelial cell; 3) decreases Kupffer cell activation and TNF, IL-1 release; 4) reduces acidosis and Na+ overload.Is ischemia preconditioning can increase the tolerance of fatty liver to hepatic ischemia-reperfusion injury or not? There is little investigation done at present in home and abroad. The present study were designed to make the fatty liver model by feeding a high-fat diet and aimed to evaluate whether ischemia preconditioning could be an effective strategy to reduce hepatic I/R injury in the presence of steatosis and to elucidate the underlying mechanisms of preconditioning on hepatic I/R injury in normal and steatotic liver.Materials and methodsExperimental animal and design: Seventy-two healthy Sprague-Dawley rats, weighing between 140 and 160 grams, were divided randomizedly into 8 groups. Rats in group 1-4 were fed a high-fat diet containing 10% lard, 2% Cholesterol, and 88%ordinary diet while rats in group 5-8 were fed ordinary diet.Water and food ad libitum until use and kept under constant environmental conditions with a 12-hour light-dark cycle. Group 1 and 5:control(NG1=9;NG5=10) rats were subjected to anesthesia and laparotomy. Group2 and 6: 1/11(NG2=9;NG6=10), rats were subjected to 40 minutes of partial ischemia followed by 90 minutes reperfusion. Group3 and 7: (NG3=8;NG7=8)ischemia preconditioning plus I/R (IPC-5+I/R), rats subjected to I/R were subjected to precious preconditioning induced by 5 minutes of ischemia and reperfusion. Group4 and 8: (NG4=8;NG8=10)( IPC-10+I/R), rats subjected to I/R were subjected to precious preconditioning induced by 5minutes of ischemia更多还原