目的观察不同低温对大鼠脊髓缺血再灌注损伤的保护作用及其对凋亡蛋白Bax、Bcl-2表达的影响。方法将60只SD大鼠随机分为4组,低温18℃实验组(深低温组),低温28℃实验组(中低温组),常温手术对照组(常温组),常温假手术组(假手术组)。前3组采用手术夹闭大鼠左肾动脉与左右髂总动脉分叉上端腹主动脉90 min致脊髓缺血,然后松开再灌注,深低温组、中低温组在阻断前20 min分别降至18、28℃,解除阻断后30 min内将体温升至37.0℃。常温组阻断前无需降温每只大鼠再灌注72 h、1周按照TARLOV法对下肢进行评分。每组分为24 h、72 h、1周3个不同时间点取L1~L5段脊髓,每个时间点5只大鼠,采用普通病理HE染色、Nissl染色,从形态学上观察脊髓组织,TUNEL法观察细胞凋亡情况,免疫组化染色及Western blot法观察脊髓组织Bax蛋白及Bcl-2蛋白表达情况。结果 TARLOV神经评分结果显示,深低温组、中低温组下肢恢复情况明显好于常温组(P<0.01),而中低温组评分又高于深低温组(P<0.01)。组织形态学观察假手术组未发现明显病理学改变,深低温组、中低温组、常温组3组均出现不同程度病理改变,且中低温组轻于深低温组,深低温组组轻于常温组;TUNEL结果显示,假手术组几乎未发现凋亡细胞,常温组神经元细胞凋亡情况较深低温组及中低温组明显。免疫组化及Western blot结果显示,深低温组、中低温组各时间点Bax蛋白表达量均低于常温组,但中低温组降低比深低温组明显,组间两两比较,差异有统计学意义(P<0.05)。深低温组、中低温组、假手术组各时间点Bcl-2蛋白表达量均高于常温组,且中低温组较深低温组高,组间两两比较,差异有统计学意义(P<0.05)。结论低温保护下肢神经功能及减少神经元的死亡,对大鼠脊髓缺血再灌注损伤有保护作用,并且可能通过抑制Bax蛋白的表达及活化Bcl-2蛋白的表达,抑制神经元凋亡发挥其保护作用。过低温度则可能通过抑制Bcl-2蛋白表达而使低温保护效果降低。 Objective To observe the protective effect of different hypothermia on spinal cord ischemia-reperfusion injury in rats and its effect on the expression of Bax and Bcl-2. Methods Sixty Sprague-Dawley rats were randomly divided into four groups: low temperature 18 ℃ experimental group (deep hypothermia group), low temperature 28 ℃ experimental group (middle low temperature group), normal temperature operation control group (normal temperature group), normal temperature sham operation group Surgery group). In the first three groups, the left anterior descending artery of the left renal artery and the common bifurcation of the right common iliac artery were surgically occluded for 90 min to induce spinal cord ischemia, and then reperfusion was released. In the deep hypothermia group and the middle and low temperature group, Drop to 18,28 ° C and raise body temperature to 37.0 ° C within 30 min of unblocking. Normal temperature group without blocking before cooling, each rat reperfusion 72 h, 1 week in accordance with the TARLOV method for lower limb score. Each group was divided into four groups at different time points: 24 h, 72 h and 1 week. L1 ~ L5 spinal cord was taken at each time point. Five rats were used at each time point. The normal pathological HE staining and Nissl staining were used to observe the morphological changes of spinal cord, Cell apoptosis was observed by TUNEL method. The expression of Bax protein and Bcl-2 protein in spinal cord tissue were detected by immunohistochemistry and Western blot. Results The results of TARLOV neurological score showed that the recovery of lower extremities in the deep hypothermia group and the moderate hypothermia group was significantly better than that in the normal temperature group (P <0.01), while it was higher in the hypothermia group than in the hypothermia group (P <0.01). Histopathological examination showed no significant pathological changes in sham operation group, the pathological changes in the three groups of hypothermia, middle and low temperature group, normal temperature group were all different, and the mild hypothermia group was lighter than the deep hypothermia group, the deep hypothermia group was lighter than the normal temperature Group; TUNEL results showed that almost no apoptotic cells were found in the sham operation group. The apoptosis of neurons in the normal temperature group was more obvious than that in the deep hypothermia group and the moderate hypothermia group. The results of immunohistochemistry and Western blot showed that the expression of Bax protein in deep hypothermia group and middle hypothermia group were lower than those in normal temperature group, but the expression of Bax protein in hypothermia group was lower than that in deep hypothermia group, and the difference was statistically significant Significance (P <0.05). The expression of Bcl-2 protein in deep hypothermia group, moderate hypothermia group and sham operation group were higher than those in normal temperature group, and were higher in hypothermia group than those in deep hypothermia group. There was significant difference between groups (P < 0.05). Conclusion Low temperature protection of lower extremity nerve function and reduction of neuronal death have a protective effect on spinal cord ischemia-reperfusion injury in rats, and may exert their protective effects on neurons by inhibiting Bax protein expression and activating Bcl-2 protein expression Protective effects. Too low temperature may reduce the effect of hypothermia by inhibiting the expression of Bcl-2 protein.