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Repolarization current in embryonic chick atrial heart cells.

J R Clay1, C E Hill, D Roitman

  • 1Laboratory of Biophysics, DIR, NINCDS, Bethesda, MD 20892.

The Journal of Physiology
|September 1, 1988
PubMed
Summary

The delayed rectifier potassium current (IK) initiates repolarization in single embryonic chick heart cells. However, it requires a small additional repolarization current (IX1) for complete action potential repolarization.

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Atownship public health centre in Ontario.

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Area of Science:

  • Cardiology
  • Electrophysiology
  • Molecular Biology

Background:

  • The action potential of cardiac cells is crucial for heart function.
  • Understanding the ionic currents responsible for cardiac action potentials is essential for diagnosing and treating heart conditions.

Purpose of the Study:

  • To measure and characterize the delayed rectifier potassium current (IK) in single cultured cells from embryonic chick atria.
  • To investigate the role of IK in the repolarization of the cardiac action potential in single cells.

Main Methods:

  • Whole-cell patch-clamp technique on single cultured cells from embryonic chick hearts.
  • Voltage-clamp steps to activate and measure IK.
  • Analysis of activation and tail current kinetics.
  • Computer simulations to model the contribution of IK to action potential repolarization.

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Main Results:

  • IK was activated by depolarizing steps positive to -30 mV, with maximum activation at +25 mV.
  • IK kinetics were voltage-dependent, with a time constant of approximately 2 s at -20 mV.
  • IK is predominantly carried by potassium ions.
  • IK alone initiated repolarization but was insufficient for the later phase; a small IX1 component was needed.

Conclusions:

  • The delayed rectifier potassium current (IK) plays a significant role in initiating cardiac action potential repolarization in single embryonic chick atrial cells.
  • Complete repolarization requires the contribution of both IK and a smaller repolarization current (IX1).
  • These findings contribute to understanding the ionic basis of cardiac electrical activity.