Journal
PROGRESS IN BIOPHYSICS & MOLECULAR BIOLOGY
Volume 105, Issue 3, Pages 162-179Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.pbiomolbio.2010.06.001
Keywords
Excitation-contraction coupling; Calcium signalling; Calcium indicators; Skeletal muscle
Categories
Funding
- NIGMS NIH HHS [R01 GM086167-02, GM 86167, R01 GM086167] Funding Source: Medline
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During excitation contraction coupling in skeletal muscle, calcium ions are released into the myoplasm by the sarcoplasmic reticulum (SR) in response to depolarization of the fibre's exterior membranes. Ca2+ then diffuses to the thin filaments, where Ca2+ binds to the Ca2+ regulatory sites on troponin to activate muscle contraction. Quantitative studies of these events in intact muscle preparations have relied heavily on Ca2+-indicator dyes to measure the change in the spatially-averaged myoplasmic free Ca2+ concentration (Delta[Ca2+]) that results from the release of SR Ca2+. In normal fibres stimulated by an action potential, Delta[Ca2+] is large and brief, requiring that an accurate measurement of Delta[Ca2+] be made with a low-affinity rapidly-responding indicator. Some low-affinity Ca2+ indicators monitor Delta[Ca2+] much more accurately than others, however, as reviewed here in measurements in frog twitch fibres with sixteen low-affinity indicators. This article also examines measurements and simulations of Delta[Ca2+] in mouse fast-twitch fibres. The simulations use a multi-compartment model of the sarcomere that takes into account Ca2+'s release from the SR, its diffusion and binding within the myoplasm, and its re-sequestration by the SR Ca2+ pump. The simulations are quantitatively consistent with the measurements and appear to provide a satisfactory picture of the underlying Ca2+ movements. (C) 2010 Elsevier Ltd. All rights reserved.
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