Calcium transients in asymmetrically activated skeletal muscle fibers

Biophysical Journal
G TrubeS R Taylor

Abstract

Skeletal muscle fibers of the frog Rana temporaria were held just taut and stimulated transversely by unidirectional electrical fields. We observed the reversible effects of stimulus duration (0.1-100 ms) and strength on action potentials, intracellular Ca2+ transients (monitored by aequorin), and contractile force during fixed-end contractions. Long duration stimuli (e.g., 10 ms) induced a maintained depolarization on the cathodal side of a cell and a maintained hyperpolarization on its anodal side. The hyperpolarization of the side facing the anode prevented the action potential from reaching mechanical threshold during strong stimuli. Variation of the duration or strength of a stimulus changed the luminescent response from a fiber injected with aequorin. Thus, the intracellular Ca2+ released during excitation-contraction coupling could be changed by the stimulus parameters. Prolongation of a stimulus at field strengths above 1.1 x rheobase decreased the amplitude of aequorin signals and the force of contractions. The decreases in aequorin and force signals from a given fiber paralleled one another and depended on the stimulus strength, but not on the stimulus polarity. These changes were completely reversible for stimulus st...Continue Reading

Citations

Jan 1, 1982·Progress in Biophysics and Molecular Biology·J R BlinksF G Prendergast
Feb 1, 1984·Journal of the American College of Cardiology·J P MorganH V Schaff
May 3, 2007·Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences·Guy Claireaux, Christel Lefrançois

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