A novel type of depolarization-activated K+ current in isolated adult rat atrial myocytes.
To determine the types of voltage-gated K+ channels controlling action potential repolarization in atrial cells, we have characterized the properties of depolarization-activated K+ channels in isolated adult rat atrial myocytes using the whole cell patch-clamp recording technique. On membrane depolarization, Ca2(+)-independent outward K+ currents in these cells begin to activate at approximately -40mV. At all test potentials, the currents activate rapidly after a delay, and there is little or no decay of the peak outward current amplitude during brief (100 ms) depolarizations. In addition, the currents show little steady-state inactivation at membrane potentials negative to -60 mV. The currents are blocked effectively by 1-5 mM 4-aminopyridine but are relatively insensitive to extracellular tetraethylammonium at concentrations up to 50 mM. Based on the measured time- and voltage-dependent properties and the pharmacological sensitivity of the currents, we suggest that the depolarization-activated K+ channels underlying the macroscopic currents in adult rat atrial myocytes are distinct from those described previously in other myocardial preparations, including adult rat ventricular myocytes. Interestingly, the outward K+ currents characterized here in isolated adult rat atrial myocytes are remarkably similar to those of several recently described "delayed rectifier" K+ channel genes isolated from rat brain cDNA libraries and expressed in Xenopus oocytes, suggesting that similar K+ currents are likely present in cells of the mammalian central nervous system.
Boyle
W A
WA
Department of Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110.
Nerbonne
J M
JM
D015761:4-Aminopyridine / Q000494:pharmacology; D000200:Action Potentials; D000818:Animals; D016275:Atrial Function; D002118:Calcium / Q000494:pharmacology; D004553:Electric Conductivity; D006321:Heart / Q000502:physiology*; D006325:Heart Atria / Q000166:cytology; D006352:Heart Ventricles / Q000166:cytology; D015640:Ion Channel Gating / Q000502:physiology; D007700:Kinetics; D008564:Membrane Potentials / Q000502:physiology; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D016276:Ventricular Function
D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D019789:Tetraethylammonium; D015761:4-Aminopyridine; D002118:Calcium