HYDROXYL RADICAL GENERATION DURING EXERCISE INCREASES MITOCHONDRIAL PROTEIN

分离的线粒体是公认的氧化剂来源 体外培养。几乎没有直接证据表明线粒体促进 然而，体内的氧化应激。模型系统研究证明 邻位酪氨酸、偏位酪氨酸和o，o4-二酪氨酸在 被羟基自由基氧化的蛋白质。以确定是否 线粒体在体内产生氧化剂，我们使用同位素稀释气体 用气相色谱-质谱法测定这些标志物的水平 在对照组和运动组大鼠的心肌中。锻炼导致50%的人 邻位酪氨酸、偏位酪氨酸和o，o4-二酪氨酸的增加。 心肌的线粒体蛋白，而不是胞浆蛋白。 这种增加是暂时的，在以下情况下水平恢复正常 训练过的动物被允许休息。也有一个过路人 运动后尿中o，o4-二氢酪氨酸水平的升高 老鼠。线粒体和尿液水平之间的关系 O，o4-二氢酪氨酸表明尿液中含有这种氧化的氨基 酸可能是氧化应激的非侵入性指标。我们的 观察还提供了直接证据，证明心肌 线粒体产生一种类似于羟基自由基的中间体 这会促进体内蛋白质的氧化。

Isolated mitochondria are well-established sources of oxidants in vitro. There is little direct evidence that mitochondria promote oxidative stress in vivo, however. Model system studies demonstrate that ortho-tyrosine, meta-tyrosine, and o,o4-dityrosine increase in proteins oxidized by hydroxyl radical. To determine whether mitochondria generate oxidants in vivo, we used isotope dilution gas chromatography-mass spectrometry to quantify levels of these markers in heart muscle of control and exercised rats. Exercise led to a 50 % increase in ortho-tyrosine, meta-tyrosine, and o,o4-dityrosine in the mitochondrial proteins but not cytosolic proteins of heart muscle. This increase was transient, and levels returned to normal when exercised animals were allowed to rest. There also was a transient increase in the level of o,o4-dityrosine in the urine of exercised rats. This relationship between mitochondrial and urine levels of o,o4-dityrosine suggests that urine assays o f this oxi dized amino acid might serve as noninvasive measures of oxidative stress. Our observations also provide direct evidence that heart muscle mitochondria produce an intermediate resembling the hydroxyl radical that promotes protein oxidation in vivo.