Calcium sparks: elementary events underlying excitation-contraction coupling in heart muscle.
Spontaneous local increases in the concentration of intracellular calcium, called "calcium sparks," were detected in quiescent rat heart cells with a laser scanning confocal microscope and the fluorescent calcium indicator fluo-3. Estimates of calcium flux associated with the sparks suggest that calcium sparks result from spontaneous openings of single sarcoplasmic reticulum (SR) calcium-release channels, a finding supported by ryanodine-dependent changes of spark kinetics. At resting intracellular calcium concentrations, these SR calcium-release channels had a low rate of opening (approximately 0.0001 per second). An increase in the calcium content of the SR, however, was associated with a fourfold increase in opening rate and resulted in some sparks triggering propagating waves of increased intracellular calcium concentration. The calcium spark is the consequence of elementary events underlying excitation-contraction coupling and provides an explanation for both spontaneous and triggered changes in the intracellular calcium concentration in the mammalian heart.
Cheng
H
H
Department of Physiology, University of Maryland School of Medicine, Baltimore 21201.
Lederer
W J
WJ
Cannell
M B
MB
D000814:Aniline Compounds; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology; D005456:Fluorescent Dyes; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000502:physiology; D008856:Microscopy, Fluorescence / Q000379:methods; D008954:Models, Biological; D009124:Muscle Proteins / Q000187:drug effects / Q000502:physiology; D009200:Myocardial Contraction / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism; D051381:Rats; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D014966:Xanthenes
D000814:Aniline Compounds; D015220:Calcium Channels; D005456:Fluorescent Dyes; D009124:Muscle Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D014966:Xanthenes; D012433:Ryanodine; C059715:Fluo-3; D002118:Calcium