Imaging of phosphoenergetic state and intracellular pH in human calf muscles after exercise by 31P NMR spectroscopy.
Phosphoenergetic and pH images in human calf muscles before and after ischemic exercise were generated by 31P NMR chemical shift imaging (CSI) with a 1.5 T standard clinical MR machine using a home-built volume coil. Acquisition of data was repeated four times with 8 x 8 phase-encoding steps and 1 s repetition time. The total acquisition time was 4 min 16 s. After 3-dimensional (3D) Fourier transformation with zero-filling, 2-dimensional (2D) images with 32 x 32 matrices of phosphocreatine (PCr), inorganic phosphate (Pi), PCr/(PCr + Pi) and pH were constructed. These metabolic images were overlaid with concurrently observed 1H MRI to locate the areas showing metabolic response. After 3 min exercise consisting of repeated plantarflexion of the foot under ischemic conditions, decreases in phosphoenergetic levels and acidosis were the most severe in the peroneus muscles, moderate in the tibialis anterior muscle, and slight in the triceps muscle of the calf. Under maintained ischemic conditions, phosphoenergetic level further decreased, but the acidosis in each muscle did not progress further. Heterogeneous metabolic and pH changes throughout the entire calf muscle were clearly demonstrated in detail by these images.
Morikawa
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S
Molecular Neurobiology Research Center, Shiga University of Medical Science, Japan.
Inubushi
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T
Kito
K
K
Tabata
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R
D000138:Acidosis / Q000378:metabolism; D000328:Adult; D004734:Energy Metabolism; D005583:Fourier Analysis; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007091:Image Processing, Computer-Assisted; D007511:Ischemia / Q000378:metabolism; D007866:Leg / Q000098:blood supply; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology; D018482:Muscle, Skeletal / Q000098:blood supply / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D010725:Phosphocreatine / Q000378:metabolism*; D010759:Phosphorus Isotopes; D005082:Physical Exertion / Q000502:physiology*
D010710:Phosphates; D010759:Phosphorus Isotopes; D010725:Phosphocreatine