Abstract
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.
| Original language | English |
|---|---|
| Pages (from-to) | 740-744 |
| Number of pages | 5 |
| Journal | Science |
| Volume | 262 |
| Issue number | 5134 |
| Publication status | Published - 29 Jan 1993 |