脂质过氧化在再灌流性肝损伤中的作用

采用低流率-再灌流模型研究脂质过氧化在再灌流性肝损伤中的作用,肝脏经过90min低速率灌流未见明显损伤,当灌流速率恢复到正常后中心静脉周围区(PC区)细胞发生迅速不可逆损害,并伴有丙二醛生成率大幅度上升,低速率灌流期间,灌流液中黄嘌呤与次黄嘌吟浓度由原来的1.5和3.6μmol·L~(-1)逐步升高至5.5和11.5μmol·L~(-1),自由基清除剂儿茶酸能使再灌流期丙二醛生成率由295 nm01·g~(-1)·h~(-1)下降至109 nmol·g~(-1)·h~(-1),并使LDH释放率减少约50％,PC区细胞死亡率减少89％,再灌流初期用氮饱和灌流液冲洗3 min,使再灌流所致的LDH释放下降约50％,PC区细胞死亡率减少84％,别嘌吟醇(2～6mmol·L~(-1))对防止再灌流性肝损伤表现出明显的剂量效应关系。 与预计结果相反低浓度别嘌呤醇(0.5～1mmol·~(-1))能增加再灌流性肝损伤,400μmol·L~(-1)黄嘌呤则使再灌流性肝损伤明显减轻,其代谢产物尿酸对降低再灌流时丙二醛生成率以及细胞损害均表现出明显的剂量反应关系。

Role of lipid peroxidation in reperfusion injury in perfused rat liver

The purpose of this study was to evaluate the possible role of lipid peroxidation in reperfusion injury in a low-flow reflow model of liver perfusion. Liver was perfused at flow rates around 25% of normal for 90 min and then at normal flow rates (4 ml ·g-1·min-1) for 30 min. When flow was restored to normal, malondialdehyde (MDA) and lactic dehydrogenase (LDH) were released into the effluent perfusate. MDA production rapidly reached values of 295 nmol·g-1·h-1 whereas LDH released from basallevel of 2.0 to 10.5 μmol ·?s-1·L-1 upon reperfusion. Trypan blue was taken up exclusively in cells in pericentral (PC) regions of the liver lobules under these conditions. Xanthine and hypoxanthine in the effluent perfusate increased steadily during the low-flow period reaching values around 5.5 and 11.5 nmol·L-1, respectively. Perfusion with nitrogen-saturated buffer for 3 min upon restoration of normal flow rate or infusion of the radical scavenger catechin (400 μmol·L-1) reduced cell damage by 50%. Infusion of allopurinol (2-6 mmol·L-1), an inhibitor of xanthine oxidase, prevented reperfusion injury in a dose-dependent manner. Taken together, these data indicate that a reperfusion injury occurs in liver upon reintroduction of oxygen which is initiated by oxidation of xanthine and hypoxanthine via xanthine oxidase and ultimately leads to production of lipid peroxides. Surprisingly, infusion of xanthine (0.4 mmol·L-1), the substrate of xanthine oxidase, reduced hepatocellular injury in reperfusion. LDH release was decreased from values around 11.5 to 3.3 μmol·s-1·L-1 and trypan blue uptake in PC regions was prevented totally by xanthine. Reperfusion injury and MDA production were also re-duced in a dose-dependent manner by uric acid, the product of xanthine metabolism via xanthine oxidase. Thus xanthine most likely reduces cell injury by producing the radical scavenger uric acid. Moreover low dose of allopurinol (up to 1 mmol·L-1) actually enhanced cell damage most likely by interfering with this mechanism. Whether or not reperfusion injury occurs in perfused liver may depend on the relative concentration of oxygen radicals to radical scavenger such as uric acid.