中文摘要：

目的研究脊髓损伤（SCI）后脊髓组织中丙二醛（MDA）的动态水平变化和神经细胞凋亡及其凋亡相关因子表达的变化，探讨活性氧（ROS）在SCI后的作用及其分子机制。方法成年雄性大鼠132只，用改良的Allen法复制大鼠急性SCI模型，致大鼠脊髓（T10）中度挫伤，采用化学比色法测定不同时间段受损脊髓组织的MDA含量；免疫组织化学法分析受损脊髓组织区域凋亡相关因子Caspase-3、Bcl-2和Bax的表达变化；荧光原位缺口末端标记法（TUNEL）检测细胞凋亡。结果SCI后6h，脊髓组织中MDA含量明显增高并维持到损伤后5d，期间在6h和3d出现两次高峰，7d基本恢复正常；SCI后6h脊髓组织中凋亡细胞开始增多，3d达高峰，以后逐渐减少，各时间点与假手术组比较有显著性的差异；Bcl-2和Bax蛋白损伤后6h开始有较多的表达，以后快速增多，5d达高峰，然后逐渐回落。Caspase-3蛋白在损伤后6h开始增多，3d达高峰，以后逐渐减少。3种凋亡相关因子在各时间点与假手术组比较有显著性差异；甲基强的松龙（MPSS）治疗组与SCI组比较：MDA含量、凋亡细胞数、凋亡因子Caspase-3和Bax表达减少，Bcl-2表达增加，并且在部分时间点有显著性差异。结论在SCI后ROS可能通过促进Caspase-3表达和降低Bcl-2／Bax之间的比值诱导神经细胞凋亡，从而加重了SCI继发性损伤。

英文摘要：

Objective To explore the effect and injury mechanism of reactive oxygen species （ROS） after spinal cord injury （SCI） through detecting the dynamic changes of malonyldialdehyed （MDA）content in spinal cord and observing neurocyte apoptosis and correlation apoptosis factor expression after SCI. Methods Totally 132 adult SD male rats were randomly divided into three groups： sham group, SCI group, methylprednisolone （MPSS） group. The SCI of SD rats was performed by Allen＇s weight dropping way to impact on the posteriors of spinal cord T10. The contents of MDA were determined by chromatometry, the expression of Caspase-3 and Bcl-2 family in the injured spinal cord was detected by immunohistochemical staining; Apoptotic cells were detected by using fluorometrie terminal deoxynucleotidyl transferase mediated dUTP nick end labeling （fluorometric TUNEL） staining. Results The content of MDA in the injured cord increased significantly after SCI, reached the peak at 6 hours and 3 days post-injury, then dropped down gradually, then was back to the normal level after 7 days. The number of TUNEL labeling positive cells of SCI group increased at 6 hours post-injury, reached the peak at 3 days, then dropped down gradually; Bcl-2, Bax protein began to increase at 6 hours post-injury, reached the peak at 5 days after injury, then dropped down gradually. Caspase-3 protein began to increase at 6 hours post-injury, reached the peak at 3 days after injury, then dropped down gradually. The content of MDA, the number of TUNEL labeling positive cells, the expression of Caspase-3 and Bax of MPSS group decreased significantly than that of SCI group at the same time, respectively, while Bcl-2 protein was up-regulated after administration of MPSS. Conclusion ROS could promote the expression of Caspase-3 and degrade the ratio of Bcl-2/Bax to induce apoptosis of neurocyte, which might play significantly role in the process of secondary SCI. In addition, MPSS exerts neuroprotective effects against ROS toxicity, which might