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Updated: Aug 26, 2026

Measurement of Maximum Isometric Force Generated by Permeabilized Skeletal Muscle Fibers
Published on: June 16, 2015
Tension development and calcium sensitivity in skinned muscle fibres of the frog
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 degrees 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 micron, the Ca2+ concentration for half maximum tension (K) was 1.6 microM. This Ca2+ concentration decreased with increasing sarcomere length; at 2.7 micron, K was 1.1 microM and at 3.1 micron, K was 0.9 microM. 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 micron by means of 5% Dextran also caused an increase in Ca sensitivity (K was 1.0 microM). At 2.7 micron, 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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