© 1995 American Heart Association, Inc.
Articles |
Description of a Nonselective Cation Current in Human Atrium
From the Departments of Pharmacology (W.J.C., C.W.C.), Pediatrics (W.J.C.), and Surgery (J.D.P.), Tulane University School of Medicine, New Orleans, La.
Correspondence to Dr William J. Crumb, Jr, Department of Pediatrics, Division of Cardiology #SL37, Tulane University School of Medicine, 1430 Tulane Ave, New Orleans, LA 70112-2699.
Abstract 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
30% of the steady state current amplitude remained. When pipette
K+ was replaced with Cs+, a similar
rapidly activating current that reversed polarity at 0 mV was
recorded. This current was seen in 100% of the cells tested from
17 different hearts (n=142), and its amplitude was 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 µmol/L, 22°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.
Key Words: humans • atrial myocytes • cation • Cs+ • electrophysiology
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