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Related Experiment Videos

Outward sodium current in beating heart cells.

D P Wellis1, L J DeFelice, M Mazzanti

  • 1Department of Anatomy and Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322.

Biophysical Journal
|January 1, 1990
PubMed
Summary

This study reveals that the outward sodium (Na) current in cardiac action potentials uses the same channels as the inward current. This finding suggests the Na action current contributes to the repolarization phase of heart action potentials.

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Area of Science:

  • Cardiovascular Physiology
  • Biophysics
  • Electrophysiology

Background:

  • The fast sodium (Na) current is crucial for the depolarization phase of cardiac action potentials.
  • Previous research has investigated the outward Na current, but its channel association remained unclear.

Purpose of the Study:

  • To determine if the outward Na current during action potentials flows through the same channels responsible for rapid depolarization.
  • To investigate the role of Na channels in both inward and outward currents in cardiac cells.

Main Methods:

  • Utilized patch clamp techniques on single, spontaneously beating embryonic chick ventricle cells.
  • Employed a two-electrode system for simultaneous recording of action potentials and patch currents.
  • Developed and applied a novel method for subtracting capacitive current.

Related Experiment Videos

  • Varied pipette potential and Na concentration, fitting corrected currents to a standard biophysical model.

    • Main Results:

    • Provided evidence that the outward Na current is carried by the same channels responsible for the inward current.
    • Observed more positive Na reversal potentials in cell-attached patch recordings from beating cells, suggesting higher intracellular Na.
    • Data supports the hypothesis that outward Na movement occurs when the action potential plateau exceeds Na reversal potentials.

    Conclusions:

    • The fast Na current channels are involved in both inward and outward ion movements during cardiac action potentials.
    • The outward Na current, driven by specific voltage conditions, likely contributes to the fast repolarization phase of cardiac action potentials.