title: Breakdown of adenine nucleotide pool in fatiguing skeletal muscle in McArdle's disease: a noninvasive 31P-MRS and EMG study.
abstract: 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.
authors.affiliation: Institute of Aerospace Medicine, German Aerospace Center (DLR e.V.), Linder Höhe, D-51170 Köln, Cologne, Germany. Jochen.Zange@dlr.de
authors.forename: Jochen
authors.initials: J
authors.lastname: Zange
authors.forename: Torsten
authors.initials: T
authors.lastname: Grehl
authors.forename: Catherine
authors.initials: C
authors.lastname: Disselhorst-Klug
authors.forename: Günter
authors.initials: G
authors.lastname: Rau
authors.forename: Klaus
authors.initials: K
authors.lastname: Müller
authors.forename: Rolf
authors.initials: R
authors.lastname: Schröder
authors.forename: Martin
authors.initials: M
authors.lastname: Tegenthoff
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Malin
authors.forename: Matthias
authors.initials: M
authors.lastname: Vorgerd
mesh_terms: 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
chemical_list: D000227:Adenine Nucleotides; D004573:Electrolytes; D000255:Adenosine Triphosphate