Hydrogen peroxide activates glibenclamide sensitive k+ channels in
llc-pk1 cells.
Filipovic, Dragana M., and W. Brian Reeves.
Division of Nephrology, Department of Internal Medicine, University
of Arkansas for Medical Sciences and the John L. McClellan Veterans
Affairs Hospital, Little Rock, AR 72205
APStracts 3:0305C, 1996.
Oxidant-induced damage has been implicated in the pathogenesis of
several forms of cellular injury. The present study employed patch
clamp methods to determine if oxidant stress leads to activation of
plasma membrane K+ channels in the renal epithelial LLC-PK1 cell
line. Exposure of cells to H2O2 (0.1 mM to 5 mM) induced a rapid
(within 5-10 minutes), dose-dependent membrane hyperpolarization.
Perforated-patch whole cell voltage-clamp studies were performed to
determine the ion selectivity of the currents underlying this H2O2
-induced cellular hyperpolarization. H202 (5 mM) produced a 6-fold
increase in the whole cell conductance. The reversal potential of the
H2O2-induced current was consistent with a K+ selective conductance.
This current was blocked almost completely by 5 mM barium and 500
[mu]M glibenclamide, but only partially by 15 mM tetraethylammonium.
Exposure of LLC-PK1 cells to 5 mM H2O2 reduced cell ATP content by
70%. To evaluate more directly the role of ATP depletion in the
activation of K+ channels, conventional whole cell patch clamp
studies were performed. Inclusion of ATP in the pipette solution
prevented H2O2-induced activation of the K+ conductance. These
findings indicate that H2O2 activates an ATP-sensitive, Ca
-independent K+ conductance in LLC-PK1 cells.
Received 13 May 1996; accepted in final form 11 September 1996.
APS Manuscript Number C258-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996