Abstract
1. Calcium sparks were examined in enzymatically dissociated mouse
cardiac ventricular cells using the calcium indicator fluo-3 and
confocal microscopy. The properties of the mouse cardiac calcium
spark are generally similar to those reported for other species.
2. Examination of the temporal relationship between the action potential
and the time course of calcium spark production showed that calcium
sparks are more likely to occur during the initial repolarization
phase of the action potential. The latency of their occurrence varied
by less than 1.4 ms (s.d.) and this low variability may be explained
by the interaction of the gating of L-type calcium channels with
the changes in driving force for calcium entry during the action
potential. 3. When fixed sites within the cell are examined, calcium
sparks have relatively constant amplitude but the amplitude of the
sparks was variable among sites. The low variability of the amplitude
of the calcium sparks suggests that more than one sarcoplasmic reticulum
(SR) release channel must be involved in their genesis. Noise analysis
(with the assumption of independent gating) suggests that > 18 SR
calcium release channels may be involved in the generation of the
calcium spark. At a fixed site, the response is close to 'all-or-none'
behaviour which suggests that calcium sparks are indeed elementary
events underlying cardiac excitation-contraction coupling. 4. A method
for selecting spark sites for signal averaging is presented which
allows the time course of the spark to be examined with high temporal
and spatial resolution. Using this method we show the development
of the calcium spark at high signal-to-noise levels.
- 10381593
- action
- aniline
- animals,
- c57bl,
- calcium
- channels,
- compounds,
- confocal,
- electric
- electrophysiology,
- factors,
- gov't,
- heart,
- inbred
- l-type,
- membrane
- mice,
- microscopy,
- myocardium,
- non-u.s.
- patch-clamp
- potentials,
- research
- signaling,
- stimulation,
- support,
- techniques,
- time
- xanthenes,
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