Breakdown of adenine nucleotide pool in fatiguing skeletal muscle in McArdle's disease: a noninvasive 31P-MRS and EMG study.
Energy metabolism and electrical muscle activity were studied in the calf muscles of 19 patients with proven McArdle's disease and in 25 healthy subjects. Phosphorus magnetic resonance spectroscopy and surface electromyography (S-EMG) were performed during two isometric muscle contractions of 3 min at 30% maximum voluntary contraction, one performed during normal perfusion and the other during applied ischemia. After about 1 min of ischemic muscle contraction in diseased muscle a significant acceleration in phosphocreatine breakdown was observed, along with a significant decrease in adenosine triphosphate. During both contractions the absence of glycolysis was shown by a significant alkalinization. Furthermore, in patients we observed a greater increase in the S-EMG amplitude than in control subjects. We conclude that early on during moderate exercise, a small number of muscle fibers reach metabolic depletion, indicated by a reduction in the adenine nucleotide pool. An increasing number of motor units, which are still in a high-energy state, are continuously recruited to compensate for muscle fatigue. This functional compartmentation may contribute to the pathophysiology of exercise intolerance in McArdle's disease.
Zange
Jochen
J
Institute of Aerospace Medicine, German Aerospace Center (DLR e.V.), Linder Höhe, D-51170 Köln, Cologne, Germany. Jochen.Zange@dlr.de
Grehl
Torsten
T
Disselhorst-Klug
Catherine
C
Rau
Günter
G
Müller
Klaus
K
Schröder
Rolf
R
Tegenthoff
Martin
M
Malin
Jean-Pierre
JP
Vorgerd
Matthias
M
D000200:Action Potentials / Q000235:genetics; D000227:Adenine Nucleotides / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000328:Adult; D004573:Electrolytes / Q000378:metabolism; D004576:Electromyography; D004734:Energy Metabolism / Q000235:genetics*; D017079:Exercise Tolerance / Q000235:genetics; D005260:Female; D006012:Glycogen Storage Disease Type V / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000235:genetics; D018763:Muscle Fatigue / Q000235:genetics*; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000503:physiopathology
D000227:Adenine Nucleotides; D004573:Electrolytes; D000255:Adenosine Triphosphate