低压缺氧大鼠脑线粒体内腺苷酸含量及能荷的变化

目的　对比研究急性和慢性缺氧暴露后脑线粒体内的能量储备和ATP生成能力 ,探讨急性缺氧致脑功能障碍和慢性缺氧适应的能量代谢机制。方法　Wistar大鼠分为对照组、急性缺氧组和慢性缺氧组。后两组分别于模拟海拔40 0 0m高原低压舱内连续缺氧暴露 3d和 3 0d ,每天 2 3 5h。缺氧组和对照组动物分别在模拟高原条件和平原条件断头处死 ,取脑组织分离线粒体。高压液相色谱分离并测量线粒体内腺苷酸库 (pool)含量 ,并计算能荷 ;以琥珀酸为氧化底物检测线粒体的ATP生成速率。结果　急性和慢性低压缺氧暴露后大鼠脑线粒体内的总腺苷酸库变化不明显 (P >0 0 5 ) ,但慢性缺氧组高于急性组 (P <0 0 5 ) ;线粒体内的ATP含量在急性和慢性缺氧时分别降低 65 1%和 3 3 5 %,慢性缺氧可部分恢复 ,但仍低于对照组 (P <0 0 5 ) ;ATP在总腺苷酸库中所占比例在急、慢性缺氧时分别是对照的 41 5 %和 42 5 %;急、慢性缺氧对线粒体内能荷均无显著影响 (P >0 0 5 ) ;急性缺氧可使以琥珀酸为底物的线粒体ATP生成速率降低 41 8%,而慢性缺氧则与对照组无显著差异 (P >0 0 5 )。结论　急性缺氧暴露可显著降低脑线粒体内的能量储备 ,而线粒体ATP生成能力降低是其原因之一 ;慢性缺氧暴露则可使其能量储备部分恢复 ,提示“线粒

Changes of adenylate pool and energy charge in mitochondria isolated from rat brain exposed to hypobaric hypoxia

Objective To investigate the mechanisms in energy metabolism of brain dysfunction during acute hypoxic exposure and adaptation to hypoxia during chronic hypoxic exposure by comparative study of the energy status and adenosine triphosphate (ATP) production ability in mitochondria of rats exposed to acute and chronic hypoxia. Methods Wistar rats were randomly divided into normoxic control group, acute hypoxia group and chronic hypoxia group. The acute and chronic hypoxic exposure models were established by exposing rats to a hypobaric chamber simulating 4 000 m above sea level for 3 days and 30 days. Then rats were sacrificed at sea level and at simulated high altitude. Brain mitochondria were isolated by centrifugation program. The size of adenylic acid pool (ATP, ADP, AMP) in mitochondria was separated and measured by high performance liquid chromatography (HPLC). The ATP production rate of mitochondria was measured by adding succinate into the response medium in isolated organelle in vitro . Results Compared with that in the normoxic control group, no change of the total size of adenylic acid pool in mitochondria was found during acute and chronic hypoxic exposures ( P >0 05). The content of adenylic acid in mitochondria in chronic hypoxia group was higher than that in acute hypoxia group ( P <0 05). The content of ATP in mitochondria decreased by 65 1% and 33 5% in acute and chronic hypoxia groups, respectively. Partial recovery of ATP content was observed in chronic hypoxia group, but APT content was still lower than that in the control group ( P <0 05). The ratio of ATP to total adenylate pool in acute and chronic hypoxia groups was respectively 41 5% and 42 5% of that in the normoxic control group. Both acute and chronic hypoxic exposures had no effects on energy charge of the mitochondria ( P >0 05). ATP production rate of oxygenating succinate in isolated organelle in vitro decreased by 41 5% in acute hypoxia group, but no significant difference was found between the chronic hypoxia group and the control group. Conclusion Acute hypoxic exposure can significantly decrease the energy reserve of brain mitochondria. The main cause is the drop of ATP production ability in mitochondria. However, chronic hypoxic exposure can partly restore the energy reserve. This suggests the role of mitochondrial adaptation in the body adaptation to hypoxia.