Pflügers Archiv

, Volume 420, Issue 2, pp 180–186 | Cite as

Role of external Ca2+ and K+ in gating of cardiac delayed rectifier K+ currents

  • Michael C. Sanguinetti
  • Nancy K. Jurkiewicz
Heart, Circulation, Respiration and Blood; Environmental and Exercise Physiology

Abstract

We sought to determine whether extracellular Ca2+ (Cae2+) and K+ (Ke+) play essential roles in the normal functioning of cardiac K+ channels. Reports by others have shown that removal of Cae2+and Ke+alters the gating properties of neural delayed rectifier (IK) and A-type K+ currents, resulting in a loss of normal cation selectivity and voltage-dependent gating. We found that removal of Cae2+and Ke+from the solution bathing guinea pig ventricular myocytes often induced a leak conductance, but did not affect the ionic selectivity or time-dependent activation and deactivation properties of IK. The effect of [K+]e on the magnitude of the two components of cardiac IK was also examined. IK in guinea pig myocytes is comprised of two distinct types of currents: IKr (rapidly activating, rectifying) and IKs (slowly activating). The differential effect of Cae2+on the two components of IK (previously shown to shift the voltage dependence of activation of the two currents in opposite directions) was exploited to determine the role of Ke+on the magnitude of IKs and IKr. Lowering [K+]e from 4 to 0 mM increased IKs, as expected from the change in driving force for K+, but decreased IKr. The differential effect of [K+]e on the two components of cardiac IK may explain the reported discrepancies regarding modulation of cardiac IK conductance by this cation.

Key words

Voltage clamp Guinea pig myocyte Cardiac potassium channels Calcium Potassium 

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Copyright information

© Springer-Verlag 1992

Authors and Affiliations

  • Michael C. Sanguinetti
    • 1
  • Nancy K. Jurkiewicz
    • 1
  1. 1.Department of PharmacologyMerck Sharp & Dohme Research Laboratories, WP26-265West PointUSA

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