Description of a Nonselective Cation Current in Human Atrium

• Published in: Circulation research Vol. 77; no. 5; pp. 950 - 956
• Main Authors: Crumb, Jr, Pigott, John D, Clarkson, Craig W
• Format: Journal Article
• Language: English
• Published: Hagerstown, MD American Heart Association, Inc 01.11.1995; Lippincott; Lippincott Williams & Wilkins Ovid Technologies
• Subjects: Age Factors; Atrial Function; Biological and medical sciences; Cations - metabolism; Cesium - pharmacology; Chloride Channels - physiology; Electrophysiology; Fundamental and applied biological sciences. Psychology; Heart; Heart Atria - cytology; Heart Atria - metabolism; Humans; In Vitro Techniques; Infant; Infant, Newborn; Middle Aged; Models, Biological; Nisoldipine - pharmacology; Ouabain - pharmacology; Potassium Channels - physiology; Sodium Channels - physiology; Vertebrates: cardiovascular system; Heart; Human; Atrium; Repolarization; Sodium; Electrophysiology; Patch clamp method; Cations; Circulatory system; Ionic current; Potassium; Myocyte
• ISSN: 0009-7330; 1524-4571
• DOI: 10.1161/01.RES.77.5.950

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 approximate equal 30% of the steady state current amplitude remained. When pipette K was replaced with Cs, a similar rapidly activating current that reversed polarity at approximate equal 0 mV was recorded. This current was seen in 100% of the cells tested from 17 different hearts (n equals 142), and its amplitude was approximate equal 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 plus minus 1.35 pA/pF, n equals 8) and pediatric (5.54 plus minus 1.04 pA/pF, n equals 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 mu mol/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.(Circ Res. 1995;77:950-956.)