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Related Experiment Videos

Repolarization currents in embryonic chick atrial heart cell aggregates.

A Shrier, J R Clay

    Biophysical Journal
    |November 1, 1986
    PubMed
    Summary

    Researchers identified two outward membrane currents, Ix1 and Ix2, in embryonic chick atrial cells. These currents play a role in action potential plateau despite the absence of a typical pacemaker current.

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    Area of Science:

    • Cardiac Electrophysiology
    • Developmental Biology
    • Ion Channel Physiology

    Background:

    • Understanding the ionic mechanisms underlying cardiac action potentials in embryonic hearts is crucial for developmental cardiology.
    • Chick embryonic atrial cells provide a model system for studying early cardiac electrical activity.
    • Previous studies have characterized various ion currents, but a comprehensive understanding of outward currents in early embryonic atrial cells is still developing.

    Purpose of the Study:

    • To characterize the outward membrane currents in aggregates of atrial cells from embryonic chick hearts.
    • To identify and differentiate components of the outward current active during the action potential plateau.
    • To develop a mathematical model of cardiac electrical activity based on measured outward currents and literature-derived inward currents.

    Main Methods:

    • Utilized the two-microelectrode voltage-clamp technique to measure membrane currents.
    • Prepared aggregates of atrial cells from 7-12-day-old chick embryonic hearts.
    • Developed a mathematical model incorporating measured time-dependent outward currents and literature data for inward currents.

    Main Results:

    • Identified two distinct outward current components, Ix1 and Ix2, active during the action potential plateau.
    • Ix1 is activated between -50 and -20 mV and exhibits inward rectification.
    • Ix2 is activated between -15 and +20 mV and shows a linear current-voltage relationship. These cells beat spontaneously despite lacking a time-dependent pacemaker current.

    Conclusions:

    • Ix1 and Ix2 are significant contributors to the repolarization phase of the action potential in embryonic chick atrial cells.
    • The presence of these outward currents supports spontaneous beating, even without a classical time-dependent pacemaker current.
    • The developed mathematical model provides a framework for understanding embryonic cardiac electrical activity based on identified ionic currents.

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