Modelling the molecular basis of cardiac repolarization
1Cardiac Bioelectricity and Arrhythmia Center, Washington University in St Louis, 290 Whitaker Hall, Campus Box 1097, One Brookings Drive, St Louis, MO 63130-4899, USA. rudy@wustl.edu
Summary
The slow delayed rectifier K+ channel (I(Ks)) creates an available reserve of channels that rapidly open on demand. This property shortens cardiac action potential duration at fast heart rates, aiding repolarization.
Area of Science:
- Cardiovascular Physiology
- Computational Biology
- Ion Channel Biophysics
Background:
- The cardiac action potential (AP) duration is critical for normal heart function.
- Rate-dependent changes in AP duration are essential for adapting to varying heart rates.
- The slow delayed rectifier K+ current (I(Ks)) plays a significant role in cardiac repolarization.
Purpose of the Study:
- To investigate the gating properties of the I(Ks) channel.
- To understand how I(Ks) gating contributes to rate-dependent repolarization of the cardiac AP.
- To elucidate the role of I(Ks) in maintaining repolarization reserve.
Main Methods:
- Utilized a computational biology approach.
- Simulated I(Ks) channel gating kinetics.
- Modeled the cardiac action potential of a mammalian ventricular myocyte.
Main Results:
- At fast heart rates, I(Ks) channels accumulate in a closed state near the open state.
- This proximity allows for rapid channel opening.
- Rapid opening generates a large repolarizing current late in the AP, shortening its duration.
Conclusions:
- I(Ks) establishes an 'available reserve' of channels.
- This reserve enables 'on-demand' opening to repolarize the AP and shorten its duration at fast rates (rate-adaptation).
- I(Ks) contributes to repolarization reserve, crucial when other repolarizing currents are impaired by disease or drugs.
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