胃肠外营养相关肝损伤机制的实验研究

目的建立幼兔胃肠外营养(PN)相关肝损伤模型,探讨氧化损伤及凋亡在PN相关肝损伤机制中的作用。方法20只新西兰种白兔随机分为对照组(母乳喂养,n=10)和PN组(n=10),PN组经右颈静脉置入硅胶管,连续24 h输注静脉营养液,10 d后比较两组间血清肝功能生化指标、肝脏病理变化及电镜下肝细胞细胞器的变化。用比色法检测肝细胞超氧化物歧化酶(SOD)活性;硫代巴比妥酸法测定肝组织丙二醛(MDA)水平;免疫印迹法检测肝细胞线粒体释放细胞色素C活性;ELISA法检测肝细胞caspase-3活性;原位末端标记法检测肝细胞凋亡。结果PN组血清胆汁酸、总胆红素、MDA水平和细胞色素C、caspase-3活性及肝细胞凋亡指数均明显高于对照组(P<0.01);而SOD活性却显著低于对照组(P<0.01)。PN组肝脏病理学观察可见门脉区炎症细胞浸润,有肝细胞变性、坏死或胆汁淤积;电镜下主要表现为胞浆空泡样变,毛细胆管微绒毛稀疏等。结论PN肝脏损伤机制可能是PN某些配方成分应用中,脂质过氧化导致肝细胞氧化损伤,同时损伤线粒体膜,促使线粒体膜通透性增加,释放细胞色素C等凋亡相关因子,激发caspase-3等级联反应,产生肝细胞凋亡,导致肝损伤。

Molecular Mechanisms of Parenteral Nutrition-Associated Liver Dysfunction

Objective To investigate the molecular mechanisms of parenteral nutrition(PN)-associated liver dysfunction. Methods Twenty New Zealand rabbits were divided into two groups: 10 rabbits in the control group(maternal fed) and 10 in PN group.The rabbits in PN group received continuous PN infusion through a silastic catheter inserted in the right jugular vein for 10 d.Then liver biochemistry analysis,histological examination and electron microscopy were performed.The hepatocyte superoxide dismutase(SOD) activity(colorimetric method) and malondialdehyde(MDA) level(thiobarbituricacid method) were measured.The hepatocyte cytochrome C activity(Wes-(tern) blotting),caspase-3 activity(ELISA) and hepatocyte apoptosis(TUNEL assay) were detected. Results The total bilirubin,bile acid,MDA levels,cytochrome C activity,caspase-3 activity and hepatocyte apoptotic rate in PN group were all significantly higher than those in the control group(P<0.01),while SOD activity in PN group was lower than that in the control group(P<0.01).In PN group,the light microscopic findings included inflammation cells infiltration and hepatic steatosis,and electron microscopy showed vacuole change in cytosol and rarefactive(microvillus) in micro-bile duct. Conclusion PN-associated liver dysfunction was related with hepatocyte oxidative injury and apoptosis.