Efficiency of work performance and contraction velocity in isotonic tetani of frog sartorius |
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Authors: | Pietro E. di Prampero Urs Boutellier Anouk Marguerat |
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Affiliation: | (1) Department of Physiology, Centre Médical Universitaire, 1, rue Michel Servet, CH-1211 Geneva 4, Switzerland;(2) Present address: Istituto di Biologia, Facoltà di Medicina e Chirurgia, Via Gervasutta 48, I-33100 Udine, Italy |
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Abstract: | Mechanical work, ATP, ADP, PC, free creatine and lactate concentrations were determined on IAA poisoned frog sartorii tetanically stimulated in humidified N, at 10°C in isotonic conditions (0.25 or 0.45 P0). Tetanus duration was 0.35 s, number of tetani was varied from 0 (rest) to 25 (exhaustion). The mechanical work performed per mole ATP+PC split (WP*) amounted on the average to 16.7 kJ/mol. It was observed, however, that wp* increased from about 13 to about 24 kJ/mol with decreasing ATP concentration from about 2 (resting value) to about 1 mol/g and that this decrease in ATP was associated with a decrease of the shortening (and relaxation) speed of the muscle to about 30% of the values observed on the first tetanus. It is concluded that the thermodynamic efficiency of muscle contraction, calculated from the ratio of wP* (measured) to the thermodynamic affinity (free energy change) of ATP hydrolysis (estimated) increases from about 0.3 to about 0.5 with decreasing ATP concentration and shortening speed.This work was supported by the Fonds National Suisse de la Recherche Scientifique, Grants 3.332.78 and 3.364.0.82 |
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Keywords: | Frog sartorius Mechanical equivalent of /content/gh0246811q46v653/xxlarge8764.gif" alt=" sim" align=" MIDDLE" BORDER=" 0" > P splitting ATP concentration Speed of shortening |
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