Calcium indicators and calcium signalling in skeletal muscle fibres during excitation-contraction coupling.

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Baylor SM, Hollingworth S

Calcium indicators and calcium signalling in skeletal muscle fibres during excitation-contraction coupling.

Prog Biophys Mol Biol. 2011 May;105(3):162-79. doi: 10.1016/j.pbiomolbio.2010.06.001. Epub 2010 Jun 25.

PubMed ID

20599552 [ View in PubMed

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Abstract

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. Ca(2+) then diffuses to the thin filaments, where Ca(2+) binds to the Ca(2+) regulatory sites on troponin to activate muscle contraction. Quantitative studies of these events in intact muscle preparations have relied heavily on Ca(2+)-indicator dyes to measure the change in the spatially-averaged myoplasmic free Ca(2+) concentration (Delta[Ca(2+)]) that results from the release of SR Ca(2+). In normal fibres stimulated by an action potential, Delta[Ca(2+)] is large and brief, requiring that an accurate measurement of Delta[Ca(2+)] be made with a low-affinity rapidly-responding indicator. Some low-affinity Ca(2+) indicators monitor Delta[Ca(2+)] 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[Ca(2+)] in mouse fast-twitch fibres. The simulations use a multi-compartment model of the sarcomere that takes into account Ca(2+)'s release from the SR, its diffusion and binding within the myoplasm, and its re-sequestration by the SR Ca(2+) pump. The simulations are quantitatively consistent with the measurements and appear to provide a satisfactory picture of the underlying Ca(2+) movements.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Calcium	Troponin C, slow skeletal and cardiac muscles	Protein	Humans	Yes	Agonist	Details