Extracellular [K+] fluctuations in voltage-clamped canine cardiac Purkinje fibers.
Membrane currents and extracellular [K+] were measured in canine Purkinje strands during voltage-clamp steps to plateau or diastolic potentials. Extracellular [K+] increased during step depolarizations and decreased during step hyperpolarizations. On hyperpolarization, the largest fraction of the K+ depletion occurred during the initial 500 ms of the voltage-clamp step and was correlated with a potassium depletion current, the id. A slower component of the depletion also occurred on hyperpolarization and had a time constant consistent with cylindrical diffusion of potassium within the Purkinje strands. On depolarization, there is an accumulation of K+ that is correlated with the plateau current ix. On termination of depolarizing test pulses, the K+ accumulation decays with a time course similar to the ix tail current. Surprisingly, no accumulation of K+ occurred during the arrhythmogenic transient inward current, TI, suggesting that the selectivity of this current should be reevaluated.
D000818:Animals; D004285:Dogs; D004553:Electric Conductivity; D006329:Heart Conduction System / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D011188:Potassium / Q000378:metabolism* / Q000494:pharmacology; D011690:Purkinje Fibers / Q000187:drug effects / Q000502:physiology*
D011188:Potassium