Dengler R, Wohlfarth K, Zierz S, Jobges M, Schubert M
Department of Neurology of the Medical University Hanover, Hanover, Germany.
Muscle Nerve. 1996 Apr;19(4):456-62. doi: 10.1002/(SICI)1097-4598(199604)19:4<456::AID-MUS5>3.0.CO;2-B.
We studied muscle fatigue and serum lactate and pyruvate levels in 20 patients with mitochondrial myopathy with progressive external ophthalmoplegia (PEO). Fatigue was assessed in the adductor pollicis muscle (AP) using a low-intensity exercise protocol (20 min). Forces (TFs) and relaxation times of ulnar nerve evoked twitches, compound muscle action potentials (CMAPs), and maximal voluntary contractions (MVCs) were monitored. Serum lactate and pyruvate levels were independently measured at rest and after exercise on a bicycle (15 min, 30 W). Most patients showed abnormal fatigue of the AP with a reduction of TFs and MVCs and normal CMAPs. The reduced TFs were significantly correlated with lactate levels at rest (r= - 0.60, P<0.05) and less so with those after exercise (r=- 0.47,P<0.05). Pyruvate levels revealed a similar correlation although they were widely scattered. We conclude that abnormal fatigue in PEO is metabolic, is localized beyond the muscle fiber membrane, and involves the electrome-chanical coupling and the contractile apparatus. Serum lactate levels at rest are good predictors of fatigue in PEO.
我们研究了20例伴有进行性眼外肌麻痹（PEO）的线粒体肌病患者的肌肉疲劳以及血清乳酸和丙酮酸水平。采用低强度运动方案（20分钟）评估拇内收肌（AP）的疲劳情况。监测尺神经诱发抽搐的肌力（TFs）和舒张时间、复合肌肉动作电位（CMAPs）以及最大自主收缩（MVCs）。在静息状态和骑自行车运动后（15分钟，30瓦）分别独立测量血清乳酸和丙酮酸水平。大多数患者表现出AP异常疲劳，TFs和MVCs降低，而CMAPs正常。TFs降低与静息时乳酸水平显著相关（r = -0.60，P<0.05），与运动后乳酸水平的相关性稍弱（r = -0.47，P<0.05）。丙酮酸水平也呈现类似的相关性，尽管其离散度较大。我们得出结论，PEO中的异常疲劳是代谢性的，位于肌纤维膜之外，涉及机电耦联和收缩装置。静息时的血清乳酸水平是PEO疲劳的良好预测指标。
