大鼠肢体缺血再灌注所致脑损伤及其机制探讨

Brain injury induced by ischemia-reperfusion of rat hindlimbs and its mechanisms

目的 :观察肢体缺血 -再灌注对脑的损伤作用 ,并探讨其可能的机制。方法 :SD大鼠随机分为正常(N)、假手术 (S)、后肢单纯缺血 (I)及缺血 -再灌注 (I-R)各时间点组。通过夹闭腹主动脉末端 4h、开放 2 - 2 4h复制I、I-R组模型。光、电镜观察脑的病理变化 ;反转录多聚酶链反应及免疫组化染色法 ,观察脑组织iNOS表达的变化及过氧亚硝基阴离子 (ONOO-)的硝基化产物硝基酪氨酸 (NT)的生成与分布 ;比色法测定脑组织MDA含量及SOD活性。结果 :①I-R组脑组织水肿 ,神经元受损较重 ,S、I组未见异常 ;②S、I、I-R组iNOS均有表达 ,I -R 6h表达量最大。I-R组大脑皮质、海马等区可见弥散分布的NT阳性神经元 ;③I -R 6h组MDA含量显著高于N、S、I组 ,SOD活性显著低于这些组 (P <0 0 5 ) ;而N、S、I组之间无显著差别。结论 :肢体I -R能引发脑损伤 ,脑内高表达的iNOS-NO

AIM: To investigate the pathologic changes in the brain and its underlying mechansims during ischemia-reperfusion of rat hindlimbs.METHODS: SD rats were divided into the normal(N), sham(S), 4 h ischemia without reperfusion(I), and 4 h ischemia-2, 6,12,18 or 24 h reperfusion (I-R) groups at random. Ischemia and ischemia-reperfusion were established with the occlusion or/and re-opening of the terminal of abdominal aorta, respectively. The pathologic changes in the brain tissue were morphologically observed. The expression of inducible nitric oxide synthase ( iNOS ) mRNA, and iNOS protein and the nitrotyrosine, a marker of peroxynitrite (ONOO -),in the brain tissue were detected with RT-PCR and immunohistochemical technique, respectively. The brain superoxide dismutase (SOD) activity and malondialdehyde (MDA) contents were spectraphotometrically measured.RESULTS: Hydropic degeneration and severe injury to neurons were only showed in I-R group. Expressions of iNOS mRNA and protein were demonstrated in I-R, I and S groups, which were maximal in I-R 6 h group. iNOS positive neurons and microglias were more spread in I-R 6 h group than those in S and I groups. NT positive neurons were localized in the cerebral cortex and hippcampus of I-R 6 h group. The contents of MDA markedly increased, while the activity of SOD significantly decreased in I-R 6 h group compared to the N, S and I groups. There were no significant changes in MDA and SOD in N, S and I groups.CONCLUSION: Severe ischemia-reperfusion of rat hindlimbs could induce brain injury, and its mechanisms might be related to enhanced expression of iNOS -NO-ONOO - in the brain.