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

Pflugers Arch. 1992 Feb;420(2):180-6. doi: 10.1007/BF00374988.


We sought to determine whether extracellular Ca2+ (Ca2+e) and K+ (K+e) play essential roles in the normal functioning of cardiac K+ channels. Reports by others have shown that removal of Ca2+e and K+e 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 Ca2+e and K+e 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 Ca2+e 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 K+e 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.

MeSH terms

  • Animals
  • Calcium / physiology*
  • Cells, Cultured
  • Extracellular Space / physiology*
  • Guinea Pigs
  • Ion Channel Gating*
  • Membrane Potentials
  • Myocardium / cytology
  • Myocardium / metabolism*
  • Potassium / physiology*
  • Potassium Channels / metabolism*
  • Potassium Channels / physiology


  • Potassium Channels
  • Potassium
  • Calcium