External Nickel Blocks Human Kv1.5 Channels Stably Expressed in CHO Cells

External Nickel Blocks Human Kv1.5 Channels Stably Expressed in CHO Cells We have investigated the actions of Nickel (Ni2+) on a human cardiac potassium channel (hKv1.5), the main component of human atrial ultra-rapid delayed rectifier current, stably expressed in Chinese hamster ovary cell line using the whole-cell voltage-clamp technique. External Ni2+ reversibly decreased the amplitude of the current in a concentration-dependent manner. The concentration for half-maximum inhibition of the current at +50 mV was 568 μm. The activation, deactivation, reactivation kinetics of the current were not affected by Ni2+. Block was not voltage-dependent but frequency-dependent block was apparent. The extent of channel block during the first pulse increased when the duration of exposure to Ni2+, prior to channel activation, was prolonged indicating that Ni2+ interacted with hKv1.5 in the closed state. The percentage of current remaining in presence of Ni2+ decreased steeply over the range of steady-state channel inactivation, consistent with an enhanced block with increased inactivation. This suggests that Ni2+ preferentially blocks nonconducting hKv1.5 channels, either in the resting or inactivated state in a concentration-dependent manner. The data indicate that the mechanisms of hKv1.5 channel inhibition by Ni2+ are distinct from those of other K+ channels. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

External Nickel Blocks Human Kv1.5 Channels Stably Expressed in CHO Cells

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Publisher
Springer-Verlag
Copyright
Copyright © Inc. by 2001 Springer-Verlag New York
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s00232-001-0052-y
Publisher site
See Article on Publisher Site

Abstract

We have investigated the actions of Nickel (Ni2+) on a human cardiac potassium channel (hKv1.5), the main component of human atrial ultra-rapid delayed rectifier current, stably expressed in Chinese hamster ovary cell line using the whole-cell voltage-clamp technique. External Ni2+ reversibly decreased the amplitude of the current in a concentration-dependent manner. The concentration for half-maximum inhibition of the current at +50 mV was 568 μm. The activation, deactivation, reactivation kinetics of the current were not affected by Ni2+. Block was not voltage-dependent but frequency-dependent block was apparent. The extent of channel block during the first pulse increased when the duration of exposure to Ni2+, prior to channel activation, was prolonged indicating that Ni2+ interacted with hKv1.5 in the closed state. The percentage of current remaining in presence of Ni2+ decreased steeply over the range of steady-state channel inactivation, consistent with an enhanced block with increased inactivation. This suggests that Ni2+ preferentially blocks nonconducting hKv1.5 channels, either in the resting or inactivated state in a concentration-dependent manner. The data indicate that the mechanisms of hKv1.5 channel inhibition by Ni2+ are distinct from those of other K+ channels.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Sep 1, 2001

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