Related Experiment Video
Updated: Aug 15, 2026

Isolation of Human Atrial Myocytes for Simultaneous Measurements of Ca2+ Transients and Membrane Currents
Published on: July 3, 2013
Role of external Ca2+ and K+ in gating of cardiac delayed rectifier K+ currents
M C Sanguinetti1, N K Jurkiewicz
1Department of Pharmacology, Merck Sharp & Dohme Research Laboratories, West Point, PA 19486.
Abstract:
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.
Related Concept Videos
Non-gated Ion Channels
Compared to the gated ion channels, the non-gated channels, also known as leakage or passive channels, have no gating mechanism.
The Role of Ion Channels in Neuronal Computation
Sometimes a single EPSP is strong enough to induce an action potential in the postsynaptic neuron. However, multiple presynaptic inputs must often create EPSPs around the same time for the postsynaptic neuron to be sufficiently depolarized to fire an action potential.
Voltage-gated Ion Channels
Generally, all voltage-gated ion channels have a 'voltage-sensing domain' that spans the lipid bilayer. The charged residues in the sensor move in response to the membrane potential changes that open the channel allowing ions movement. There are several types of...
G-Protein Gated Ion Channels
Sensory organs,...
Electrophysiology of Normal Cardiac Rhythm
Cardiac Action Potential
The cardiac action potential process involves a series of phases characterized by the movement of ions across the cardiac cell membranes, leading to the depolarization and repolarization of the cardiac myocytes.
Ionic Basis of Cardiac Action Potentials

