title: 31P NMR saturation transfer study of the creatine kinase reaction in human skeletal muscle at rest and during exercise.
abstract: The creatine kinase reaction has been studied by 31P NMR in exercising human calf muscle. Quantitative analysis of high energy phosphates and saturation transfer study of the creatine kinase flux in the direction of ATP synthesis (Vfor) were performed at rest and during exercise. As expected, exercise induced a [PCr] decrease (from 28.5 +/- 0.9 to 21.9 +/- 1.5 mM, P < 0.01) matched by a Pi increase (from 4.5 +/- 0.2 to 8.9 +/- 1.8 mM, P = 0.06). pHi and [ATP] remained unchanged. Vfor did not change from rest (12.4 +/- 0.9 mM s(-1)) to moderate exercise and decreased at the highest exercise level (8.4 +/- 1.4 mM s(-1), P = 0.006). This observation differs from the prediction of the creatine kinase rate equation, showing an increase in the flux with exercise intensity. Computations suggest that this discrepancy arises from metabolite compartmentalization and/or from the reaction kinetics of a dead end complex stabilized by planar anions.
authors.affiliation: Department of Radiology and Medical Imagery, Catholic University of Louvain, Louvain-La-Neuve, Belgium.
authors.forename: J F
authors.initials: JF
authors.lastname: Goudemant
authors.forename: M
authors.initials: M
authors.lastname: Francaux
authors.forename: I
authors.initials: I
authors.lastname: Mottet
authors.forename: R
authors.initials: R
authors.lastname: Demeure
authors.forename: M
authors.initials: M
authors.lastname: Sibomana
authors.forename: X
authors.initials: X
authors.lastname: Sturbois
mesh_terms: D000328:Adult; D003402:Creatine Kinase / Q000378:metabolism*; D015444:Exercise; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007866:Leg; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D018482:Muscle, Skeletal / Q000201:enzymology*; D012146:Rest
chemical_list: D003402:Creatine Kinase