Taylor D J, Kemp G J, Woods C G, Edwards J H, Radda G K
MRC Biochemical and Clinical Magnetic Resonance Unit, John Radcliffe Hospital, Oxford, UK.
J Neurol Sci. 1993 Jun;116(2):193-200. doi: 10.1016/0022-510x(93)90325-s.
Skeletal muscle function of 15 patients with myotonic dystrophy (dystrophia myotonica, DM) was investigated using 31P magnetic resonance spectroscopy to evaluate bioenergetics and intracellular pH at rest and during exercise and recovery. Results from DM patients, normal controls and mitochondrial myopathy patients were compared in order to assess the possible contribution of abnormal mitochondrial metabolism to muscle dysfunction in DM. In resting DM muscle, intracellular pH (pHi) was normal, but there were significant elevations in the concentration ratios of Pi/ATP, phosphomonoesters/ATP and phosphodiesters/ATP. In patients with the most severe exercise intolerance the phosphocreatine/ATP ratio was also reduced. Resting muscle of 11 mitochondrial myopathy patients showed similar changes to those of the most exercise-intolerant DM patients. In exercising DM muscle, energy stores were rapidly depleted as in mitochondrial myopathy. Muscle acidified in all subjects, but in DM the decrease in pHi was less than in normal muscle. Recovery half-times for phosphocreatine, Pi and ADP were normal in DM but slow in mitochondrial myopathy. The initial rate of phosphocreatine repletion after exercise was rapid in DM, consistent with high [ADP], but slow in mitochondrial myopathy in spite of elevated [ADP]. Because recovery is an oxidative process, we conclude that there was no decrease in the oxidative capacity of the muscles in this group of DM patients. In the subjects in whom it could be measured, the rate of recovery of intracellular pH was greater in the 3 DM patients (0.14, 0.15 and 0.16 U/min) than in the 7 normal controls (0.08-0.12 U/min, mean 0.10). The results do not rule out a minor abnormality in glycogenolysis, but they suggest that the failure to acidify normally during exercise is probably due to rapid proton efflux.
使用31P磁共振波谱对15例强直性肌营养不良（萎缩性肌强直，DM）患者的骨骼肌功能进行了研究，以评估静息、运动及恢复过程中的生物能量学和细胞内pH值。比较了DM患者、正常对照者和线粒体肌病患者的结果，以评估线粒体代谢异常对DM患者肌肉功能障碍的可能影响。在静息的DM肌肉中，细胞内pH值（pHi）正常，但Pi/ATP、磷酸单酯/ATP和磷酸二酯/ATP的浓度比显著升高。在运动不耐受最严重的患者中，磷酸肌酸/ATP比值也降低。11例线粒体肌病患者的静息肌肉表现出与运动不耐受最严重的DM患者相似的变化。在运动的DM肌肉中，能量储备如线粒体肌病一样迅速耗尽。所有受试者的肌肉均发生酸化，但在DM中pHi的下降小于正常肌肉。DM患者中磷酸肌酸、Pi和ADP的恢复半衰期正常，但线粒体肌病患者中则较慢。运动后磷酸肌酸补充的初始速率在DM中较快，与高[ADP]一致，但在线粒体肌病中尽管[ADP]升高却较慢。由于恢复是一个氧化过程，我们得出结论，这组DM患者的肌肉氧化能力没有下降。在可测量的受试者中，3例DM患者（分别为0.14、0.15和0.16 U/min）细胞内pH值的恢复速率高于7例正常对照者（0.08 - 0.12 U/min，平均0.10）。结果不排除糖原分解存在轻微异常，但提示运动期间不能正常酸化可能是由于质子快速外流所致。
