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Related Experiment Videos

Internal and external K+ help gate the inward rectifier.

I S Cohen1, D DiFrancesco, N K Mulrine

  • 1Department of Physiology and Biophysics, State University of New York, Stony Brook 11794.

Biophysical Journal
|January 1, 1989
PubMed
Summary
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Internal potassium levels significantly impact cardiac iK1 channel function. Reduced internal potassium slows iK1 activation and alters its voltage dependence, potentially contributing to abnormal heart electrical activity during ischemia.

Area of Science:

  • Cardiology
  • Electrophysiology
  • Ion Channel Physiology

Background:

  • Myocardial ischemia causes significant reductions in intracellular potassium ([K+]) in cardiac Purkinje fibers.
  • These ionic shifts are hypothesized to contribute to abnormal cardiac electrical activity.

Purpose of the Study:

  • To investigate the role of internal and external potassium concentrations ([K+]) on the gating of the inward rectifier potassium current (iK1).
  • To understand how changes in internal potassium affect iK1 channel function in cardiac Purkinje myocytes.

Main Methods:

  • Utilized the whole-cell patch-clamp technique on isolated Purkinje myocytes.
  • Manipulated internal and external potassium concentrations to assess effects on iK1 gating.

Main Results:

Related Experiment Videos

  • Increased external [K+] affected iK1 similarly to other preparations, enhancing conductance and shifting activation.
  • Reduced internal [K+] (145 to 25 mM) significantly slowed iK1 activation rate.
  • Lower internal [K+] reversed the voltage dependence of iK1 recovery from deactivation and caused a smaller positive shift in the activation midpoint compared to the reversal potential shift.

Conclusions:

  • Internal potassium concentration plays a crucial role in the gating of the iK1 channel.
  • Alterations in internal [K+] during ischemia may significantly contribute to changes in myocardial electrical properties.