低温对脑缺血再灌注期间海马ATP含量和羟自由基生成的影响

目的研究低温对脑缺血再灌注期间海马ATP和羟自由基（OH·）含量的影响，并探讨二者的变化与延迟性神经元死亡的关系。方法沙土鼠前脑缺血再灌注模型，缺血时间10min。随机将动物分为假手术组、常温组和低温组，后两组又分为再灌注6h、48h、96h三个亚组。每组13只动物，其中5只用于海马组织形态学观察，另8只用于ATP、ADP、AMP和OH-含量测定。ATP、ADP、AMP含量测定采用高效液相紫外检测器法，采用水杨酸捕捉法结合高效液相及电化学检测器法测定OH·含量。结果再灌注96h，常温组海马CA1区存活锥体细胞数目仅为假手术组的5％（P〈0．01），而低温组为假手术组的45％，明显多于常温组（P〈0．01）。常温组各再灌注时间点海马ATP含量和腺苷酸池（ATP＋ADP＋AMP）含量均明显低于假手术组（P〈0．01）。除再灌注6h外，低温组海马ATP和腺苷酸池含量均明显高于常温组（P〈0．05）。常温组再灌注6h，海马2，3-DHBA含量明显高于假手术组和低温组（P〈0．01或P〈0．05），但再灌注48h和96h，三组间海马2，3-DHBA含量已无显著性差异。结论延迟性神经元死亡主要与脑缺血后持续的细胞能量代谢障碍有关，而低温可通过减轻细胞能量代谢障碍，起到减少延迟性神经元死亡的作用。

Effect of Hypothermia on ATP and Hydroxyl Radical Levels in Hippocampus during Cerebral Ischemia/Reperfusion

OBJECTIVE To study the effect of hypothermia on ATP and hydroxyl radical levels in hippocampus during cerebral ischemia/reperfnsion, and investigate the relationship between the change of their content and delayed neuronal death. METHODS Forebrain ischemia in gerbils was produced by occlusion of bilateral common carotid arteries using aneurysm clamps, and the insult time was 10 min. Gerbils were randomly divided into sham -operated group, normothermia group and hypotbermia group. Both normothermia group and hypothermia group were further divided into 3 subgroups according to the reperfusion time （6 h, 48 h and 96 h）. The brain temperature in all gerbils during cerebral ischemia was kept at 38 ±0.2℃, and it was kept at 30 ±0.2℃ within 6 h of reperfusion in hypothermia group. However, the brain temperature in normothermia group was kept at 38 ± 0.2℃. The number of surviving neurons in hippoempal CA1 sector in 100 um^2 was counted （n = 5 ）. ATP, ADP, AMP and hydroxyl radical levels were determined by high liquid chromatography （ n = 8 ）. RESULTS The number of surviving neurons in hippocampal CA1 sector after reperfusion 96 h in normothermia group was only 5 ±2/100um^2, much less than that in sham - operated group （96 ± 12/100 um^2 ） （ P 〈 0.01 ）. The number of surviving neurons in hippocampal CA1 sector after reperfusion 96 h in hypothermia group was 45 ± 13/100 um^2, much more than that in normothermia group （ P 〈 0.01 ）. ATP and adenine nucleotide pool levels in hippocampus in normothermia group significantly decreased after reperfusion （ P 〈 0.01 ）. ATP and adenine nucleotide pool levels in hippocampus in hypothermia group were much more than that in normothermia group after reperfusion 48 h and 96 h （ P 〈0.05）. The 2,3 - DHBA outputs after reperfusion 6 h in normothermia group increased by 132% of that in shamoperated group （ P 〈 0. 01 ） , but there was no significant difference of 2,3 -DHBA outputs between normothermia group and sham -operated group after reperfusion 48 h and 96 h. There was also no significant difference of 2,3 - TDHBA outputs between hypothermia group and sham - operated group. The 2,3 - DHBA outputs after reperfusion 6 h in hypothermia group was much lower than that in normothermia group （ P 〈 0.05）. CONCLUSION The persist failure of energy metabolism could lead to the delayed neuronal death after cerebral ischemia. Hypothermia could prevent delayed neuronal death by attenuating the persist failure of energy metabolism.