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Abstract #3234

31P MRS of Resting Muscle at 7T: Differences in the Alkaline PH Compartment Between Different Muscles and Sedentary and Elite Trained Athletes

Hermien E. Kan1, Joep van Oorschot2, Beatrijs H.A. Wokke3, Maarten J. Versluis1, Nadine B. Smith1, Andrew G. Webb1, Jeroen A.L. Jeneson2

1C.J. Gorter Center, department of radiology, Leiden University Medical Center, Leiden, Netherlands; 2Biomedical NMR Laboratory, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands; 3Department of neurology, Leiden University Medical Center, Leiden, Netherlands

Non-invasive determination of mitochondrial content is an important objective in clinical and sports medicine. Previously, a peak 0.4 ppm downfield from the cytosolic Pi resonance (Pi1) was found in resting skeletal muscle that was tentatively attributed to mitochondrial Pi (Pi2). Here we show a consistently higher Pi2 signal in soleus (SOL) versus tibialis anterior (TA) muscle, as well as in trained versus untrained subjects. Since these results are in quantitative agreement with known differences in oxidative capacity between SOL and TA and trained versus untrained subjects, they support our hypothesis that the Pi2 resonance originates from the mitochondrial compartment in muscle.