Description of a nonselective cation current in human atrium.
Ion currents were examined in isolated human atrial myocytes by using the whole-cell patch-clamp technique. When currents were recorded with a K(+)-containing pipette solution, depolarizing voltage pulses elicited a rapidly activating outward current that decayed to an apparent steady state. Exposure of cells to 10 mmol/L 4-aminopyridine markedly reduced current amplitude; however, a rapidly activating current that was approximately 30% of the steady state current amplitude remained. When pipette K+ was replaced with Cs+, a similar rapidly activating current that reversed polarity at approximately 0 mV was recorded. This current was seen in 100% of the cells tested from 17 different hearts (n = 142), and its amplitude was approximately 40% of the amplitude of the steady state current recorded in the presence of pipette K+. The current amplitude was not significantly different in cells isolated from adult (6.31 +/- 1.35 pA/pF, n = 8) and pediatric (5.54 +/- 1.04 pA/pF, n = 9) hearts. Studies designed to determine the charge-carrying species indicated that changes in bath Cl- concentration had no effect on either the amplitude or the reversal potential of this current, whereas removal of pipette Cs+ and bath Na+ dramatically reduced this current. In addition, this current was not modulated by either isoproterenol (1 mumol/L, 22 degrees C) or cell swelling. This study provides the first description of a nonselective cation current in human atrial myocytes, which may play an important role in repolarization in human atria.
Crumb
W J
WJ
Department of Pharmacology, Tulane University School of Medicine, New Orleans, LA 70112-2699, USA.
Pigott
J D
JD
Clarkson
C W
CW
D000367:Age Factors; D016275:Atrial Function; D002412:Cations / Q000378:metabolism; D002586:Cesium / Q000494:pharmacology; D018118:Chloride Channels / Q000502:physiology; D004594:Electrophysiology; D006325:Heart Atria / Q000166:cytology / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007223:Infant; D007231:Infant, Newborn; D008875:Middle Aged; D008954:Models, Biological; D015737:Nisoldipine / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology*; D015222:Sodium Channels / Q000502:physiology*
D002412:Cations; D018118:Chloride Channels; D015221:Potassium Channels; D015222:Sodium Channels; D002586:Cesium; D015737:Nisoldipine; D010042:Ouabain