title: Skeletal muscle ATP synthesis and cellular H(+) handling measured by localized (31)P-MRS during exercise and recovery.
abstract: (31)P magnetic resonance spectroscopy (MRS) is widely used for non-invasive investigation of muscle metabolism dynamics. This study aims to extend knowledge on parameters derived from these measurements in detail and comprehensiveness: proton (H(+)) efflux, buffer capacity and the contributions of glycolytic (L) and oxidative (Q) rates to ATP synthesis were calculated from the evolutions of phosphocreatine (PCr) and pH. Data are reported for two muscles in the human calf, for each subject and over a wide range of exercise intensities. 22 subjects performed plantar flexions in a 7T MR-scanner, leading to PCr changes ranging from barely noticeable to almost complete depletion, depending on exercise protocol and muscle studied by localized MRS. Cytosolic buffer capacity was quantified for the first time non-invasively and individually, as was proton efflux evolution in early recovery. Acidification started once PCr depletion reached 60-75%. Initial and end-exercise L correlated with end-exercise levels of PCr and approximately linear with pH. Q calculated directly from PCr and pH derivatives was plausible, requiring fewer assumptions than the commonly used ADP-model. In conclusion, the evolution of parameters describing cellular energy metabolism was measured over a wide range of exercise intensities, revealing a relatively complete picture of muscle metabolism.
authors: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Austria.|MR Centre of Excellence, Medical University of Vienna, Austria.
authors: Georg B
authors: GB
authors: Fiedler
authors: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Austria.|MR Centre of Excellence, Medical University of Vienna, Austria.
authors: Albrecht I
authors: AI
authors: Schmid
authors: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Austria.|MR Centre of Excellence, Medical University of Vienna, Austria.|Division of Endocrinology and Metabolism, Department of Internal Medicine III, Medical University of Vienna, Austria.
authors: Sigrun
authors: S
authors: Goluch
authors: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Austria.|MR Centre of Excellence, Medical University of Vienna, Austria.
authors: Kiril
authors: K
authors: Schewzow
authors: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Austria.|MR Centre of Excellence, Medical University of Vienna, Austria.
authors: Elmar
authors: E
authors: Laistler
authors: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Austria.|MR Centre of Excellence, Medical University of Vienna, Austria.
authors: Fabian
authors: F
authors: Niess
authors: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Austria.
authors: Ewald
authors: E
authors: Unger
authors: Department of Clinical Pharmacology, Medical University of Vienna, Austria.
authors: Michael
authors: M
authors: Wolzt
authors: Department of Pharmaceutical Chemistry, Semmelweis University, Budapest, Hungary.|Research Group of Drugs of Abuse and Doping Agents, Hungarian Academy of Sciences, Budapest, Hungary.
authors: Arash
authors: A
authors: Mirzahosseini
authors: Department of Musculoskeletal Biology and MRC-Arthritis Research UK Centre for Integrated Research into Musculoskeletal Ageing (CIMA), Faculty of Health &Life Sciences, University of Liverpool, UK.
authors: Graham J
authors: GJ
authors: Kemp
authors: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Austria.|MR Centre of Excellence, Medical University of Vienna, Austria.
authors: Ewald
authors: E
authors: Moser
authors: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Austria.|MR Centre of Excellence, Medical University of Vienna, Austria.
authors: Martin
authors: M
authors: Meyerspeer
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D011522:Protons
chemical_list: D011522:Protons; D000255:Adenosine Triphosphate