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KMID : 1123820070090020001
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Health & sports medicine
2007 Volume.9 No. 2 p.1 ~ p.11
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Quantifying proton release and uptake from the metabolites and reactions of the phosphagen and glycolytic energy systems in skeletal muscle
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Robert, A. Robergs
Kwon Young-Sub
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Abstract
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Within the applied physiological sciences, the belief persists that lactic acid is produced by muscle during intense exercise and is the cause of the proton (H+) load of metabolic
acidosis. This belief is not supported by metabolic biochemistry or research. Application of organic and biochemical fact reveals that lactate production consumes not produces a H+, and that H+ release from metabolism can occur from several reactions of glycolysis as well as ATP
hydrolysis. To quantify such H+ exchange, the dissociation constants of multiple competing cations to the metabolites of the phosphagen and glycolytic energy systems within skeletal
muscle were used to compute best estimates of the H+coefficients (fraction of H+ consumed or released) for specific chemical reactions. Results revealed that for pH conditions of 6.0 and 7.0, respectively, H+ coefficients (-’ve values = H+ release) for the creatine kinase, adenylate kinase, AMP deaminase and ATPase reactions were 0.8 and 0.97, -0.13 and -0.02, 1.2 and 1.09, and -0.01 and -0.66, respectively. Lactate production always consumes 1 H+ across the physiological
pH range. For glycolysis fueled by glycogen and ending in either pyruvate or lactate, H+ coefficients for pH 6.0 and 7.0 are -3.97 and -2.01, and -1.96 and -0.01, respectively. The reaction
of glycolysis that has the greatest H+ release is the glyceraldehydes-3-phosphate dehydrogenase reaction, with H+ coefficients for pH 6.0 and 7.0 of -1.58 and -0.76,
respectively. Each of glycoloysis and ATP hydrolysis accounts for the H+ load of muscle metabolism.
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KEYWORD
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H+ coefficient, metabolic acidosis, lactate, glycolysis, ATP hydrolysis
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