模拟高原缺氧大鼠脑线粒体UCP活性与含量的变化及其对线粒体能量合成的影响

Effects of brain mitochondrial uncoupling protein content and activity in rat exposed to hypoxia simulating high altitude on mitochondrial energy synthesis

目的观察模拟高原暴露大鼠脑线粒体UCP活性和含量的改变,探讨其对线粒体能量合成功能的影响。方法健康成年SD大鼠置于模拟海拔5000m低压舱中,23h/d,连续3d。差速离心法分离大鼠脑组织线粒体,Clark氧电极法测定线粒体的呼吸活性,罗丹明123法测定线粒体膜电位,高压液相色谱法测定腺苷酸的含量,用3H-GTP结合法测定线粒体UCP活性及含量。结果高原缺氧导致大鼠脑线粒体解偶联蛋白与3H-GTP结合的解离常数Kd下降37%,结合3H-GTP的最大量Bmax增加2.9倍(P<0.01);线粒体的呼吸ST3氧耗减为对照组的83.1%,而ST4则升高28%,RCR降为对照的66.67%(P<0.01);相关分析显示,ST4与反映UCP活性的Kd呈显著负相关,而与UCP含量Bmax呈显著正相关(P<0.01);同时线粒体内ATP含量仅为对照组的58.4%(P<0.01),线粒体膜电位显著下降(P<0.01)。结论模拟高原缺氧暴露可增加脑线粒体解偶联蛋白活性和含量,揭示缺氧时线粒体的呼吸氧耗及能量的生成的改变与关系。

Objective To observe the changes of rat brain mitochondrial uncoupling protein （UCP） content and activity, and explore the effect of UCP on mitochondrial energy metabolism during hypoxia exposure. Methods Adult SD rats were set randomly into control and hypoxia group （n = 8 in each group）. The rats of hypoxia group were put into a hypobaric chamber simulating 5000-meter high altitude for 3 days （ 23 h/d）. The brain mitochondria was isolated by centrifugation. Mitochondrial oxidative respiratory function was measured by Clark oxygen electrode. Mitochondrial membrane potential was detected by Rhodamine123 method. The content of adenine nucleotide pool （ATP, ADP, AMP） in mitochondria was measured by high performance liquid chromatography. UCP content and activity were detected by [ ^3H ]-GTP binding method. Results High altitude hypoxia resulted in significant increase of UCP activity and a 2.9-fold rise of UCP content of rats （P 〈0. 01 ）. Mitochondrial state 3 respiration, respiratory control rate decreased respectively to 83.1% and 66.7% of control group, while the state 4 respiration increased by 28% of control group （P 〈 0.01 ）. From the correlation test, ST4 was in a negative line regression with Kd and a positive one with Bmax. Mitochondrial ATP content in hypoxia group decreased to 58.4% of control group （P 〈 0.01 ）. The membrane potential was decrease to 80% of control group （P 〈 0.01 ）. Conclusion Hypoxia can increase the content and activity of brain mitochondrial UCP that affects mitochondrial respiratory oxygen consumption and energy production.