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Spontaneous and Repetitive Calcium Transients in C2C12 Mouse Myotubes during In Vitro Myogenesis
Author(s) -
Lorenzon Paola,
Giovannelli Aldo,
Ragozzino Davide,
Eusebi Fabrizio,
Ruzzier Fabio
Publication year - 1997
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.1997.tb01429.x
Subject(s) - myogenesis , ryanodine receptor , biophysics , calcium , cytosol , chemistry , coupling (piping) , myocyte , voltage dependent calcium channel , in vitro , microbiology and biotechnology , biology , biochemistry , materials science , enzyme , organic chemistry , metallurgy
Fluorescence videomicroscopy was used to monitor changes in the cytosolic free Ca 2+ concentration ([Ca 2+ ]i in the mouse muscle cell line C2C12 during in vitro myogenesis. Three different patterns of changes in [Ca 2+ ]i were observed: (i) [Ca 2+ ]i oscillations; (ii) faster Ca 2+ events confined to subcellular regions (localized [Ca 2+ ]i spikes) and (iii) [Ca 2+ ]i spikes detectable in the entire myotube (global [Ca 2+ ]i spikes). [Ca 2+ ]i oscillations and localized [Ca 2+ ]i spikes were detectable following the appearance of caffeine‐sensitivity in differentiating C2C12 cells. Global [Ca 2+ ]i spikes appeared later in the process of myogenesis in cells exhibiting coupling between voltage‐operated Ca 2+ channels and ryanodine receptors. In contrast to [Ca 2+ ]i oscillations and localized [Ca 2+ ]i spikes, the global events immediately stopped when cells were perfused either with a Ca 2+ ‐free solution, or a solution with TTX, TEA and verapamil. To explore further the mechanism of the global [Ca 2+ ]i spikes, membrane currents and fluorescence signals were measured simultaneously. These experiments revealed that global [Ca 2+ ]i spikes were correlated with an inward current. Moreover, while the depletion of the Ca 2+ stores blocked [Ca 2+ ]i oscillations and localized [Ca 2 ]i spikes, it only reduced the amplitude of global [Ca 2+ ]i spikes. It is suggested that, during the earlier stages of the myogenesis, spontaneous and repetitive [Ca 2+ ]i changes may be based on cytosolic oscillatory mechanisms. The coupling between voltage‐operated Ca 2+ channels and ryanodine receptors seems to be the prerequisite for the appearance of global [Ca 2+ ]i spikes triggered by a membrane oscillatory mechanism, which characterizes the later phases of the myogenic process.