title: Relation between in vivo and in vitro measurements of skeletal muscle oxidative metabolism.
abstract: The relationships between in vivo (31)P magnetic resonance spectroscopy (MRS) and in vitro markers of oxidative capacity (mitochondrial function) were determined in 27 women with varying levels of physical fitness. Following 90-s isometric plantar flexion exercises, calf muscle mitochondrial function was determined from the phosphocreatine (PCr) recovery time constant, the adenosine diphosphate (ADP) recovery time constant, the rate of change of PCr during the initial 14 s of recovery, and the apparent maximum rate of oxidative adenosine triphosphate (ATP) synthesis (Q(max)). Muscle fiber type distribution (I, IIa, IIx), citrate synthase (CS) activity, and cytochrome c oxidase (COX) activity were determined from a biopsy sample of lateral gastrocnemius. MRS markers of mitochondrial function correlated moderately (P < 0.05) with the percentage of type IIa oxidative fibers (r = 0.41 to 0.66) and CS activity (r = 0.48 to 0.64), but only weakly with COX activity (r = 0.03 to 0.26, P > 0.05). These results support the use of MRS to determine mitochondrial function in vivo.
authors.affiliation: Pennington Biomedical Research Center, Louisiana State University, 6400 Perkins Road, Baton Rouge, Louisiana 70808-4124, USA. larsonde@pbrc.edu
authors.forename: D E
authors.initials: DE
authors.lastname: Larson-Meyer
authors.forename: B R
authors.initials: BR
authors.lastname: Newcomer
authors.forename: G R
authors.initials: GR
authors.lastname: Hunter
authors.forename: D R
authors.initials: DR
authors.lastname: Joanisse
authors.forename: R L
authors.initials: RL
authors.lastname: Weinsier
authors.forename: M M
authors.initials: MM
authors.lastname: Bamman
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000328:Adult; D001706:Biopsy; D002950:Citrate (si)-Synthase / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000502:physiology; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D008928:Mitochondria / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D010725:Phosphocreatine / Q000378:metabolism
chemical_list: D010725:Phosphocreatine; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D003576:Electron Transport Complex IV; D002950:Citrate (si)-Synthase