Voltage-activated elementary calcium release events in isolated mouse skeletal muscle fibers.
J Membrane Biol. 2008-11-18; 226(1-3): 43-55
DOI: 10.1007/s00232-008-9138-0
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Csernoch L(1), Pouvreau S, Ronjat M, Jacquemond V.
Author information:
(1)Department of Physiology, Medical and Health Science Center, University of
Debrecen, Debrecen, Hungary.
The elementary Ca(2+)-release events underlying voltage-activated myoplasmic
Ca(2+) transients in mammalian muscle remain elusive. Here, we looked for such
events in confocal line-scan (x,t) images of fluo-3 fluorescence taken from
isolated adult mouse skeletal muscle fibers held under voltage-clamp conditions.
In response to step depolarizations, spatially segregated fluorescence signals
could be detected that were riding on a global increase in fluorescence. These
discrete signals were separated using digital filtering in the spatial domain;
mean values for their spatial half-width and amplitude were 1.99 +/- 0.09 microm
and 0.16 +/- 0.005 DeltaF/F(0) (n = 151), respectively. Under control
conditions, the duration of the events was limited by the pulse duration. In
contrast, in the presence of maurocalcine, a scorpion toxin suspected to disrupt
the process of repolarization-induced ryanodine receptor (RyR) closure, events
uninterrupted by the end of the pulse were readily detected. Overall results
establish these voltage-activated low-amplitude local Ca(2+) signals as inherent
components of the physiological Ca(2+)-release process of mammalian muscle and
suggest that they result from the opening of either one RyR or a coherently
operating group of RyRs, under the control of the plasma membrane polarization.
DOI: 10.1007/s00232-008-9138-0
PMCID: PMC2796304
PMID: 19015802 [Indexed for MEDLINE]