深低温停循环下犬海马组织神经细胞凋亡及脑保护的实验研究

Experimental study of neuron apoptosis in hippocampus and neuroprotection during deep hypothermic circulatory arrest in dogs

目的观察深低温停循环下犬海马组织中神经细胞凋亡情况及对凋亡相关基因bcl-2和bax表达的影响，探讨间断选择性顺行脑灌注对深低温停循环的脑保护机制。方法健康成年杂种犬（18—22kg）18只，随机均分为3组：对照组即常温体外循环组（A组）；深低温停循环（deep hypothermic circulatory arrest，DHCA）组（B组）；深低温停循环＋间断选择性顺行脑灌注（intermittent selective antegrade cerebral perfusion，ISACP）组（C组）。术后取出海马组织，采用SABC法观察海马组织bcl-2和bax表达情况。在透射电镜（TEM）下观察海马组织的细胞形态学变化。结果电镜下，A组无神经细胞凋亡，B组可见明显神经细胞凋亡改变，C组仅见少量神经细胞凋亡。SABC法观察显示在B组中，bax表达明显高于其它两组（P〈0．01），而在C组中bcl-2表达明显高于其它两组（P〈0.01）。结论深低温停循环下，bax表达增强，使得凋亡发生，而在深低温停循环下给予间断选择性顺行脑灌注时，bcl-2表达增强，bax表达减弱，从而抑制了神经细胞凋亡的发生，具有脑保护作用。

AIM To observe the neuron apoptosis in hippocampus of dogs and the effect on the expression of related gene bcl-2 and bax during deep hypothermic circulatory arrest （DHCA） and to study the neuroprotection mechanism of intermittent selective antegrade cerebral perfusion. METHODS Eighteen healthy adult dogs （18 -22 kg） were randomly divided into three groups （6 dogs in each group）. The dogs in group A, B and C respectively received common temperature cardiopulmonary bypass, DHCA and intermittent selective antegrade cerebral perfusion during DHCA. After operation the hippocampus was removed immediately. Immunohistochemistry assay was used to observe the changes of the expression of bcl- 2 and bax. The morphology of the hippocampal neurons was examined by transmission electron microscopy （TEM）. RESULTS The level of bax expression in group B was higher than that in group A or C （P 〈0.01 ）. The level of bcl-2 expression in group C was higher than that in group A or B （P 〈0.01 ）. CONCLUSION The increased expression of bax may promote the neuron apoptosis during DHCA. Intermittent selective antegrade cerebral perfusion may up-regulate bcl-2 and down -regulate bax during DHCA, which inhibits the neuron apoptosis.