Taylor D J, Bore P J, Styles P, Gadian D G, Radda G K
Mol Biol Med. 1983 Jul;1(1):77-94.
The metabolic state of human muscle in various functional states has been investigated by the non-invasive technique of 31P nuclear magnetic resonance. The concentrations of phosphocreatine, ATP and inorganic phosphate as well as intracellular pH in the flexor digitorum superficialis have been measured during rest, dynamic exercise and recovery from exercise. The observed relationship between phosphocreatine utilization and decrease in intracellular pH during aerobic exercise indicates that lactate production only becomes significant after more than 60% of the phosphocreatine is used up. Surprisingly intracellular pH may reach as low a value as 5.9 to 6.1, indicating that phosphofructokinase is still partially active at pH 6.0. There is no metabolic recovery if the muscle is made ischaemic following exercise, implying that glycolysis is switched off as soon as exercise is stopped. Lactic acidosis is not the cause of this and presumably Ca2+ is needed to maintain the activation of phosphorylase kinase. The time-course of phosphocreatine recovery after exercise reflects the rate of oxidative metabolism, while pH recovery probably represents H+ ion export from the muscle cell. The dynamics of metabolic changes can now be observed with a time resolution of 10 to 60 seconds and thus disturbances in energy metabolism can be readily detected in several pathological states.
通过³¹P核磁共振的非侵入性技术，对人体肌肉在各种功能状态下的代谢状态进行了研究。在静息、动态运动以及运动恢复过程中，测量了指浅屈肌中磷酸肌酸、三磷酸腺苷（ATP）和无机磷酸盐的浓度以及细胞内pH值。有氧运动期间观察到的磷酸肌酸利用与细胞内pH值下降之间的关系表明，只有在超过60%的磷酸肌酸被消耗后，乳酸生成才变得显著。令人惊讶的是，细胞内pH值可能低至5.9至6.1，这表明磷酸果糖激酶在pH值为6.0时仍部分活跃。如果运动后使肌肉缺血，则不会有代谢恢复，这意味着运动一停止，糖酵解就会关闭。乳酸酸中毒不是其原因，可能需要Ca²⁺来维持磷酸化酶激酶的活性。运动后磷酸肌酸恢复的时间进程反映了氧化代谢的速率，而pH值的恢复可能代表H⁺离子从肌肉细胞中输出。现在可以以10至60秒的时间分辨率观察代谢变化的动态，因此在几种病理状态下可以很容易地检测到能量代谢的紊乱。
