N-乙酰半胱氨酸对重症急性胰腺炎大鼠肠屏障保护作用机理的实验研究

目的观察N-乙酰半胱氨酸（NAC）对重症急性胰腺炎（SAP）大鼠肠屏障功能的保护作用及其可能机理。方法将80只Wistar大鼠随机（随机数字表法）分为正常对照组（CON组,n=8）、假手术组（SO组,n=24）、SAP组（n=24）及NAC组（n=24）,后3组再随机（随机数字表法）分为6、12及24 h 3个时间点组,每个时间点组8只大鼠。通过胰胆管逆行注射5%牛磺胆酸钠的方法制作大鼠SAP模型,SO组大鼠则通过胰胆管逆行注射生理盐水。NAC组大鼠于造模前1 h经腹腔注射NAC,而SO组和SAP组大鼠于相应时间点经腹腔注射生理盐水。CON组大鼠不做任何处理,麻醉后直接取右心室血5 mL及回肠组织约5 cm,余3组大鼠则于术后6、12及24 h麻醉后取材。检测血浆淀粉酶（AMY）、C-反应蛋白（CRP）、内毒素、D-乳酸及二胺氧化酶（DAO）含量;检测回肠组织总超氧化物歧化酶（T-SOD）、髓过氧化物酶（MPO）及丙二醛（MDA）含量;观察回肠上皮细胞的凋亡情况、回肠组织的病理学改变并对其进行评分;检测回肠组织bax和bcl-2 mRNA及其蛋白的表达水平。结果与同时相SAP组比较,NAC组大鼠各时相的血浆CRP水平均较低（P〈0.05）,而AMY水平在12 h和24 h时较低（P〈0.05）;NAC组大鼠的DAO、内毒素及D-乳酸水平在12 h和24 h时均较低（P〈0.05）,但DAO水平在6 h时高于SAP组（P〈0.05）;NAC组大鼠各时相回肠组织中的MPO及MDA水平均较低（P〈0.05）,而T-SOD水平则在12 h和24 h时较高（P〈0.05）;NAC组大鼠回肠上皮细胞的凋亡指数均较低（P〈0.01）,组织病理学评分在12 h及24 h时亦较低（P〈0.05）;NAC组大鼠回肠组织中bax mRNA及其蛋白的表达水平均较低（P〈0.05）,而bcl-2 mRNA及其蛋白的表达水平则均较高（P〈0.05）。结论 NAC对SAP大鼠的肠屏障功能具有保护作用,其机理除了抗氧化作用外,还可能与其抗凋亡作用有关。

Experimental Study of Protective Effects of N-Acetylcysteine on The Intestinal Barrier in Rats with Severe Acute Pancreatitis

Objective To investigate the effects of N-acetylcysteine（NAC） on the intestinal barrier in rats with severe acute pancreatitis（SAP） and its possible mechanism.Methods Eighty Wistar rats were randomly（random number method） divided into normal control group（CON group,n=8）,sham operation group（SO group,n=24）,SAP group（n=24）,and NAC group（n=24）,then the rats of latter 3 groups were sub-divided into 6,12,and 24 hours group,each time point group enrolled 8 rats,respectively.Rats of CON group didn＇t receive any treatment.SAP rat models were established by injecting 5.0% sodium taurocholate into the biliary-pancreatic duct for SAP group and NAC group,while rats of SO group were injected normal saline instead of sodium taurocholate.The rats of NAC group were given an intraperitoneal injection of NAC at 1 hour before operation,and the rats of SO group and SAP group were given an intraperitoneal injection of normal saline instead at the same time.Rats of CON group were sacrificed to get ileum（about 5？cm） and blood from right ventricular（5？mL） for further test,and rats of the other 3 groups were sacrificed at 6,12,and 24？hours after operation.Then the levels of amylase（AMY）,C-reactive protein（CRP）,endotoxin,D-lactic acid,and diamine oxidase（DAO） in plasma,the levels of superoxide dismutase（T-SOD）,myeloperoxidase（MPO）,and malondialdehyde（MDA） in ileum tissues were tested.Apoptosis of mucosal cells in ileum tissues was determined by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling（TUNEL）.Pathological changes in ileum tissues were observed and scored.Expression levels of bax and bcl-2？mRNA in ileum tissues were determined by real-time fluorescence quantitative PCR（real-time PCR）,and related proteins were tested by Western blot method,respectively.Results Compared with SAP group at the same time point,the levels of CRP in NAC group were lower at all the 3 time points（P0.05） and AMY were lower at 12 and 24 hours（P0.05）,levels of DAO,endotoxin,and D-lactic acid were lower at 12 and 24 hours（P0.05）,but level of DAO was higher than SAP group at 6 hours（P0.05）.Compared with SAP group at the same time point,the levels of MPO and MDA in ileum tissues were lower in NAC group at all the 3 time points（P0.05）,but levels of T-SOD increased significantly at 12 and 24 hours（P0.05）.Compared with SAP group at the same time point,the apoptosis indexes were lower in NAC group at all the 3 time points（P0.01）,and pathologic scores of ileum tissues were lower at 12 and 24 hours（P0.05）.The pathological changes under a light microscope were observed better in NAC group than that of SAP group at each time point.Moreover,compared with SAP group at the same time point,the expression levels of bax mRNA and protein were lower in NAC group at all the 3 time points（P0.05）,while higher in bcl-2 mRNA and protein（P0.05）.Conclusions NAC can protect the function of small intestinal barrier,and can alleviate SAP-induced injury of the intestinal mucosa.In addition to antioxidant effects,the underlying mechanisms also may include the anti-apoptotic effects.