Control of oxidative metabolism and oxygen delivery in human skeletal muscle: a steady-state analysis of the work/energy cost transfer function.
The concept of transfer function for organ performance (work output vs. biochemical input) is developed for skeletal and cardiac muscle under steady-state exercise conditions. For metabolic control by the ADP concentration, the transfer function approximates a Michaelis-Menten hyperbola. Variation of the work identifies metabolic operating points on the transfer function corresponding to ADP concentrations or to a ratio of inorganic phosphate to phosphocreatine that can be determined by phosphorus nuclear magnetic resonance. This operating point is characterized by the fraction (V/Vmax) of maximal activity of oxidative metabolism in the steady state. This quantity appears to be useful in predicting the degree to which metabolic homeostasis is effective; poorly controlled metabolic states can readily be identified and are used in the diagnosis and therapy of metabolic disease in the organs of neonates and adults.
D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004734:Energy Metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia / Q000378:metabolism; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008931:Mitochondria, Muscle / Q000378:metabolism; D009132:Muscles / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism; D010725:Phosphocreatine / Q000378:metabolism; D005082:Physical Exertion
D010710:Phosphates; D010725:Phosphocreatine; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D010100:Oxygen