Delayed rectifier potassium current (IK) in latent atrial pacemaker cells isolated from cat right atrium

Zhengfeng Zhou, Stephen L. Lipsius

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    3 Scopus citations

    Abstract

    Whole-cell recording techniques were used to study the delayed rectifier K+ current (IK) in latent pacemaker cells isolated from cat right atrium, From a holding potential of -40 mV, depolarizing clamp steps elicited L-type Ca2+ current followed by an increasing outward current (IK). The time course of tail current amplitudes parallelled that of the time-dependent activation of outward current. Activation of IK exhibited a sigmoidal time course that was best fit by a power function where the activation variable was raised to the second power. The voltage-dependence of IK activation exhibited a sigmoidal relationship between -40 and +30 mV. The half-maximal activation voltage and slope factor were -21.9±1.3 and 13.8±0.9 mV respectively (n=6). The fully activated I/V relationship of IK was linear between -100 and -30 mV and inwardly rectified at more positive voltages. Following IK activation, hyperpolarizations more negative than about -50 mV elicited tail currents that consisted of both IK deactivation and If activation. A subtraction protocol was used to isolate IK tail currents. In 5.4 mM extracellular [K+], IK tail currents exhibited a reversal potential of -78.2±0.3 mV (n=6). The reversal potential of IK was linearly related to log extracellular [K] and the slope was 51.5 mV per ten-fold change in extracellular [K]. At -70 mV, IK tail currents decayed as a single exponential function with a time constant of 159±16 ms (n=6). These results indicate that latent atrial pacemakers exhibit IK activated by depolarization. IK appears to consist of one current component. At voltages compátible with the maximum diastolic potential (-70 mV) IK tail currents are relatively small and IK decays much more rapidly than If activation. We conclude that in right atrial latent pacemakers IK may contribute to repolarization of the action potential and the time course of the initial phase of the pacemaker potential.

    Original languageEnglish (US)
    Pages (from-to)341-347
    Number of pages7
    JournalPflügers Archiv European Journal of Physiology
    Volume426
    Issue number3-4
    DOIs
    StatePublished - Feb 1 1994

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    Keywords

    • Cardiac pacemaker cells
    • Electrophysiology
    • Potassium
    • Voltage clamp

    ASJC Scopus subject areas

    • Physiology
    • Clinical Biochemistry
    • Physiology (medical)

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