Kemp G J, Taylor D J, Styles P, Radda G K
MRC Biochemical and Clinical Magnetic Resonance Unit, John Radcliffe Hospital, Oxford, UK.
NMR Biomed. 1993 Jan-Feb;6(1):73-83. doi: 10.1002/nbm.1940060112.
We show how quantitative information about proton handling in human skeletal muscle in exercise and recovery can be obtained by 31P MRS and illustrate this with data from metabolic disorders. Proton production, proton efflux and passive buffering can be distinguished by comparing changes in [phosphocreatine] and pH at the end of exercise and by calculating ATP turnover during ischaemic exercise and in the 'natural experiment' of myophosphorylase deficiency (McArdle's disease). We calculate the effective buffer capacity to be 20-30 mmol/L/pH unit (slykes), somewhat lower than published measurements made in vitro but similar to other values obtained in vivo. This analysis is applied to data from normal muscle and a variety of disease states to estimate proton efflux during recovery and ATP production during exercise: (i) proton efflux during recovery is pH-dependent, reaching a 10 mmol/L/min at pH 6.2, and is increased in some cases of mitochondrial myopathy and in hypertension; (ii) glycogenolytic ATP production during exercise can reach 25 mmol/L/min in normal muscle and correlates approximately with [Pi] at the start of aerobic exercise and throughout ischaemic exercise; (iii) oxidative ATP production can reach 20-25 mmol/L/min and (as during recovery) correlates approximately with [Pi].
我们展示了如何通过31P磁共振波谱法获取运动和恢复过程中人类骨骼肌质子处理的定量信息，并以代谢紊乱的数据为例进行说明。通过比较运动结束时[磷酸肌酸]和pH值的变化，以及计算缺血运动期间和肌磷酸化酶缺乏症（麦克尔迪氏病）的“自然实验”中的ATP周转率，可以区分质子产生、质子外流和被动缓冲。我们计算出有效缓冲能力为20 - 30 mmol/L/pH单位（斯利克斯），略低于体外发表的测量值，但与体内获得的其他值相似。该分析应用于正常肌肉和各种疾病状态的数据，以估计恢复过程中的质子外流和运动期间的ATP产生：（i）恢复过程中的质子外流依赖于pH值，在pH 6.2时达到10 mmol/L/min，在某些线粒体肌病和高血压病例中增加；（ii）正常肌肉运动期间糖原分解产生的ATP可达25 mmol/L/min，且在有氧运动开始时和整个缺血运动过程中与[无机磷酸盐]大致相关；（iii）氧化产生的ATP可达20 - 25 mmol/L/min，并且（如在恢复过程中）与[无机磷酸盐]大致相关。
