Two Distinct K+ Channels in Lamprey (Lampetra fluviatilis) Erythrocyte Membrane Characterized by Single Channel Patch Clamp

Two Distinct K+ Channels in Lamprey (Lampetra fluviatilis) Erythrocyte Membrane Characterized by... Two channels, distinguished by using single-channel patch-clamp, carry out potassium transport across the red cell membrane of lamprey erythrocytes. A small-conductance, inwardly rectifying K+-selective channel was observed in both isotonic and hypotonic solutions (osmolarity decreased by 50%). The single-channel conductance was 26 ± 3 pS in isotonic (132 mm K+) solutions and 24 ± 2 pS in hypotonic (63 mm K+) solutions. No outward conductance was found for this channel, and the channel activity was completely inhibited by barium. Cell swelling activated another inwardly rectifying K+ channel with a larger inward conductance of 65 pS and outward conductance of 15 pS in the on-cell configuration. In this channel, rectification was due to the block of outward currents by Mg2+ and Ca2+ ions, since when both ions were removed from the cytosolic side in inside-out patches the conductance of the channel was nearly ohmic. In contrast to the small-conductance channel, the swelling-activated channel was observed also in the presence of barium in the pipette. Neither type of channel was dependent on the presence of Ca2+ ions on the cytosolic side for activity. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Two Distinct K+ Channels in Lamprey (Lampetra fluviatilis) Erythrocyte Membrane Characterized by Single Channel Patch Clamp

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Publisher
Springer-Verlag
Copyright
Copyright © Inc. by 1998 Springer-Verlag New York
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s002329900369
Publisher site
See Article on Publisher Site

Abstract

Two channels, distinguished by using single-channel patch-clamp, carry out potassium transport across the red cell membrane of lamprey erythrocytes. A small-conductance, inwardly rectifying K+-selective channel was observed in both isotonic and hypotonic solutions (osmolarity decreased by 50%). The single-channel conductance was 26 ± 3 pS in isotonic (132 mm K+) solutions and 24 ± 2 pS in hypotonic (63 mm K+) solutions. No outward conductance was found for this channel, and the channel activity was completely inhibited by barium. Cell swelling activated another inwardly rectifying K+ channel with a larger inward conductance of 65 pS and outward conductance of 15 pS in the on-cell configuration. In this channel, rectification was due to the block of outward currents by Mg2+ and Ca2+ ions, since when both ions were removed from the cytosolic side in inside-out patches the conductance of the channel was nearly ohmic. In contrast to the small-conductance channel, the swelling-activated channel was observed also in the presence of barium in the pipette. Neither type of channel was dependent on the presence of Ca2+ ions on the cytosolic side for activity.

Journal

The Journal of Membrane BiologySpringer Journals

Published: May 1, 1998

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