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Updated: Jul 27, 2026
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Isolation and Kv Channel Recordings in Murine Atrial and Ventricular Cardiomyocytes
Published on: March 12, 2013
Two components of the delayed rectifier potassium current, IK, in rabbit sino-atrial node cells
Experimental Physiology
|September 1, 1996
Summary
Rabbit sino-atrial node cells possess two delayed rectifier potassium currents, rapid (IKr) and slow (IKs). IKs contributes significantly to the overall current, especially at positive potentials, and IKr influences pacemaker activity.
Area of Science:
- Cardiac Electrophysiology
- Ion Channel Function
Background:
- The sino-atrial (SA) node is crucial for heart rhythm.
- Delayed rectifier potassium currents (IK) play a role in cardiac repolarization and pacemaking.
- Understanding IK components in SA node cells is vital for comprehending cardiac electrical activity.
Purpose of the Study:
- To characterize the components of the delayed rectifier potassium current (IK.tall) in rabbit SA node cells.
- To investigate the distinct properties and contributions of the rapid (IKr) and slow (IKs) components of IK.
- To determine the role of IKr and IKs in SA node cell pacemaking.
Main Methods:
- Whole-cell voltage clamp technique using amphotericin-permeabilized patches in isolated rabbit SA node cells.
- Envelope of tails test to analyze IK decay kinetics.
- Pharmacological separation of IK components using dofetilide (IKr blocker) and propofol (IKs blocker).
Main Results:
- IK.tall in SA node cells comprises two components, similar to IKr and IKs found in other cardiac myocytes.
- Dofetilide selectively blocked IKr, revealing a drug-insensitive current (IKs).
- IKs contributes to IK.tall, with its contribution increasing at more positive membrane potentials.
- The ratio of IKs to IKr in tail currents was 0.3-0.4:1 at -40 mV after a +40 mV clamp pulse.
- Dofetilide slowed spontaneous SA node cell activity, indicating IKr's role in pacemaking.
Conclusions:
- Rabbit SA node cells exhibit distinct rapid and slow components of the delayed rectifier potassium current.
- The slow component (IKs) significantly contributes to the overall delayed rectifier current, particularly at depolarized potentials.
- The rapid component (IKr) is essential for the pacemaker activity of SA node cells.
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