Two mechanisms for termination of individual Ca2+ sparks in skeletal muscle.
Ca(2+) sparks are brief, localized elevations of myoplasmic [Ca(2+)] caused by release of increments of Ca(2+) via sarcoplasmic reticulum Ca(2+) release channels in muscle. The properties of individual sparks provide information regarding the opening of sarcoplasmic reticulum Ca(2+) channels within functioning cells. Here we use high-speed confocal microscopy to show that individual Ca(2+) sparks activated by membrane depolarization in single frog skeletal muscle fibers can be terminated prematurely by repolarization. Thus, either voltage sensor deactivation on repolarization or release channel inactivation during continued depolarization can terminate the Ca(2+) release channel activity underlying voltage-activated Ca(2+) sparks in skeletal muscle.
Lacampagne
A
A
Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, 108 North Greene Street, Baltimore, MD 21201, USA.
Klein
M G
MG
Ward
C W
CW
Schneider
M F
MF
D000814:Aniline Compounds; D000818:Animals; D001001:Anura; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000378:metabolism; D008564:Membrane Potentials; D018613:Microscopy, Confocal; D018715:Microscopy, Video; D008954:Models, Biological; D008958:Models, Molecular; D018485:Muscle Fibers, Skeletal / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D014966:Xanthenes
D000814:Aniline Compounds; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D019837:Ryanodine Receptor Calcium Release Channel; D014966:Xanthenes; C059715:Fluo-3; D002118:Calcium