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Voltage-activated elementary calcium release events in isolated mouse skeletal muscle fibers.

Abstract : 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.
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Submitted on : Thursday, July 2, 2009 - 4:45:25 PM
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Laszlo Csernoch, Sandrine Pouvreau, Michel Ronjat, Vincent Jacquemond. Voltage-activated elementary calcium release events in isolated mouse skeletal muscle fibers.. Journal of Membrane Biology, Springer Verlag (Germany), 2008, 226 (1-3), pp.43-55. ⟨10.1007/s00232-008-9138-0⟩. ⟨inserm-00401126⟩



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