Tension development and calcium sensitivity in skinned muscle fibres of the frog |
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Authors: | G. J. M. Stienen T. Blangé B. W. Treijtel |
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Affiliation: | (1) Department of Physiology, University of Amsterdam, Meibergdreef 15, NL-1105 AZ Amsterdam, The Netherlands |
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Abstract: | Calcium activated isometric tension development was measured in single skinned muscle fibres of the ileofibularis muscle of the frog. The experiments were carried out at 5°C, pH=6.9, 1 mM free Mg2+ and an ionic strength of 160 mM. A Hill curve was fitted to the isometrically developed tension at different Ca2+ concentrations by means of a non-linear least mean square approximation. At a sarcomere length of 2.15 m, the Ca2+ concentration for half maximum tension (K) was 1.6 M. This Ca2+ concentration decreased with increasing sarcomere length; at 2.7 m, K was 1.1 M and at 3.1 m, K was 0.9 M. Therefore, Ca sensitivity is increased at larger sarcomere lengths. Consequently, the optimal sarcomere length for tension development shifted to larger values when the Ca2+ concentration was lowered. Osmotic compression of the fibre at 2.15 m by means of 5% Dextran also caused an increase in Ca sensitivity (K was 1.0 M). At 2.7 m, addition of 5% Dextran hardly affected the Ca sensitivity. The possible role of the interfilament spacing in the explanation of these results discussed. |
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Keywords: | Muscle Muscle contraction Calcium sensitivity |
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