不同高压氧预处理方案对兔脊髓缺血再灌注损伤的影响

Effect of different programs of hyperbaric oxygen preconditioning on spinal cord ischemia-reperfusion injury in rabbits

目的探讨不同高压氧预处理方案对兔脊髓缺血再灌注损伤的影响。方法新西兰大白兔45只，月龄4～5月，体重2．0～2．5kg，随机分为5组：假手术组（s组，n=5）开腹剥离左肾动脉下段腹主动脉但不阻断血流，20min后关腹；脊髓缺血再灌注组（IR组，n=10）采用左。肾动脉下段腹主动脉阻断法建立脊髓缺血再灌注损伤模型，缺血20min后恢复灌注；不同方案高压氧预处理组（H1-3组，n=10）分别接受连续5d（H1组）、10d（H2组）或20d（H3组）高压氧预处理（2．5ATA，吸入氧浓度100％），1h／d，末次高压氧预处理结束后24h时，建立脊髓缺血再灌注模型。再灌注48h时，采用修正Tarlov评分，评价后肢运动功能。然后取L脊髓节段，分别行HE、TUNEL和Fluoro—JadeB染色，计数脊髓正常神经元、凋亡神经元和变性神经元。结果与S组比较，IR组后肢运动功能评分和脊髓前角正常神经元计数降低（P〈0．01）；与IR组比较，H1组和H2组后肢运动功能评分和脊髓前角正常神经元计数升高，凋亡神经元计数和变性神经元计数降低（P〈0．01），H1组各指标差异无统计学意义（P〉0．05）；H1组和H2组各指标比较差异无统计学意义（P〉0．05）；与H1组和H2组比较，心组后肢运动功能评分和脊髓前角正常神经元计数降低，凋亡神经元计数和变性神经元计数升高（P〈0．01）。结论连续5d或10d高压氧预处理（2．5ATA，吸入氧浓度100％）可减轻脊髓缺血再灌注损伤；而连续20d高压氧预处理无神经保护作用。

Objective To investigate the effect of different programs of preconditioning with hyperbaric oxygen （HBO） on spinal cord ischemia-reperfusion injury （I/R） in rabbits. Methods Forty-five New Zealand rabbits aged 4-5 months weighing 2.0-2.5 kg were randomly divided into 5 groups ： group S, sham operation （ n = 5）; group IR, spinal cord I/R injury （n = 10）; group H1-2, the animals were pretreated with 100% 02 at 2.5 ATA 1 h/d for 5 （group H1）, 10 （group H2 ）, or 20 （group H3 ） consecutive days respectively 24 h before spinal cord I/R. The animals were anesthetized with iv pentobarbital sodium 30 mg/kg. The artery in the ear and left femoral artery were eannulated for proximal and distal mean blood pressure monitoring. Spinal cord ischemia was produced by cross-clamping of abdominal aorta distal to renal artery for 20 min. Hind-limb motor function was assessed at 48 h after reperfusion according to the modified criteria established by Tarlov （0 = no spontaneous movement, 4 = normal motor function）. The animals were then killed and the L5 segment of the spinal cord was removed for detection of neuronal survival （by HE staining）, apoptosis （by TUNEL） and degeneration （by Fluoro- Jade B staining） . Results Preconditioning with 5 or 10 d of HBO improved the hind-limb motor function and preserved more normal neurons in the spinal cord after t/R injury. Both apoptotic and degenerative cell death were attenuated in H1 and H2 groups. There was no significant difference in hind-limb motor dysfunction and the number of normal neurons in the lumbar spinal cord between H3 group and I/R group. Conclusion Preconditioning with 5 d or 10 d HBO induces tolerance against spinal cord I/R injury, whereas preconditioning with 20 d of HBO fails to protect the spinal cord from I/R injury.