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First published online July 23, 2003

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Effects of temperature and extracellular pH on metabolites: kinetics of anaerobic metabolism in resting muscle by ³¹P- and ¹H-NMR spectroscopy

Alessandra Vezzoli^1,*, Maristella Gussoni², Fulvia Greco³ and Lucia Zetta³

¹ Istituto di Bioimmagini e Fisiologia Molecolare, CNR, Milan, Italy
² Dipartimento di Scienze e Tecnologie Biomediche, Università di Milano, Milan, Italy
³ Istituto per lo Studio delle Macromolecole, CNR, Milan, Italy

View larger version (27K): [in a new window]   Fig. 1. Concentration versus time plots of (A) phosphocreatine (PCr), (B) inorganic phosphate (Pi), (C) adenosine triphosphate (ATP), (D) phosphomonoesters (PME) and (F) lactate (La) at the experimental temperature of 15°C. Concentration levels are expressed in µmol g-1 muscle wet mass. (E) Intracellular pH (pHi) versus time plots are also shown. All data corresponding to the different experimental extracellular pH (black, 7.9; white, 7.3; grey, 7.0) are shown. Time zero corresponds to the beginning of anaerobiosis (arbitrarily set when the PCr peak started decreasing sharply).

View larger version (26K): [in a new window]   Fig. 2. Concentration versus time plots of (A) phosphocreatine (PCr), (B) inorganic phosphate (Pi), (C) adenosine triphosphate (ATP), (D) phosphomonoesters (PME) and (F) lactate (La) at the experimental temperature of 25°C. Concentrations are expressed in µmol g-1 muscle wet mass. (E) Intracellular pH (pHi) versus time plots are also shown. All data corresponding to the different experimental extracellular pH (black, 7.9; white, 7.3; grey, 7.0) are shown. Time zero corresponds to the beginning of anaerobiosis.

View larger version (23K): [in a new window]   Fig. 3. Time-dependent changes of PCr (circles) and La (squares) concentrations (A) and pHi (inverted triangles) and pHe (diamonds) values (B) are shown. All the data are from the additional set of experiments performed at 25°C where initial pHe value was 7.9 and the muscle pHi initial values were varied: high (filled symbols; preparation 1) and low (open symbols; preparation 2). The brackets in B indicate the corresponding pHi and pHe values (i.e. the proton gradient).

View larger version (24K): [in a new window]   Fig. 4. Cumulative changes in pHi (pH) and in proton load (P) due to changes in [PCr] (expressed in µmol g-1 wet mass) at (A) 15°C and (B) 25°C. The data are related to the different experimental pHe (black, 7.9; white, 7.3; grey, 7.0). Point zero (the origin of the axis) corresponds to the values registered at the beginning of the experiments. The diagonal lines through the origin, calculated in the range where the change in pH was due solely to changes in [PCr], have a slope equal to -1/ß (see text).

View larger version (19K): [in a new window]   Fig. 5. pH gradient (A) and lactate accumulation (B) plotted as a function of time. The data, corresponding to the different experimental extracellular pH (7.9, black; 7.3, white; 7.0, grey), are the same as in Fig. 2.

View larger version (17K): [in a new window]   Fig. 6. 31P-NMR spectrum of an isolated gastrocnemius muscle at T=25°C and an initial pHe of 7.0 registered at 20 h from the beginning of the experiment. Peak assignment: phenylphosphonate (PPA); phosphomonoesters (PME); inorganic phosphate (Pi); phosphocreatine (PCr); , and ß ATP groups.