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Regulation of Oxidative and Glycogenolytic ATP Synthesis in Exercising Rat Skeletal Muscle Studied by 31 P Magnetic Resonance Spectroscopy
Author(s) -
Kemp G. J.,
Sanderson A. L.,
Thompson C. H.,
Radda G. K.
Publication year - 1996
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/(sici)1099-1492(199609)9:6<261::aid-nbm430>3.0.co;2-b
Subject(s) - oxidative phosphorylation , skeletal muscle , nuclear magnetic resonance , nuclear magnetic resonance spectroscopy , chemistry , spectroscopy , oxidative metabolism , oxidative stress , biophysics , biochemistry , biology , metabolism , endocrinology , physics , quantum mechanics
31 P magnetic resonance spectroscopy measurements of pH and the concentrations of orthophosphate and phosphocreatine were used to estimate rates of glycogenolytic and oxidative ATP synthesis in rat leg muscle during 6 min sciatic nerve stimulation at different rates (1–4 Hz). To study the regulation of glycogenolysis during exercise, the apparent "glycogenolytic capacity' ( L MAX ) was calculated from glycogenolytic ATP synthesis rate and orthophosphate concentration as a measure of the Ca 2+ ‐dependent activation of glycogen phosphorylase. This was found to be proportional to the total ATP synthesis rate ( F ), and to decline with time; expressed relative to total ATP turnover rate as L MAX / F , its initial value was 2.9±0.6, declining with half‐time 1.4±0.4 min. The apparent "mitochondrial capacity' ( Q MAX ), calculated from oxidative ATP synthesis rate and [ADP], was independent of ATP turnover rate, but increased with half‐time 0.8±0.1 min to 29±2 mmol kg −1 min −1 : thus [ADP] was the predominant but not the only influence on oxidative ATP synthesis. Numerical simulation shows that time‐dependent changes in L MAX >/ F exert a strong influence on pH and on the concentrations of phosphocreatine and ADP