Hydrogen peroxide activates glibenclamide-sensitive K+ channels in LLC-PK1 cells.
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 to 5 mM) induced a rapid (within 5-10 min), 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. H2O2 (5 mM) produced a sixfold 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 microM 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, Ca2+-independent K+ conductance in LLC-PK1 cells.
Filipovic
D M
DM
Department of Internal Medicine, University of Arkansas for Medical Sciences and the John L. McClellan Veterans Affairs Hospital, Little Rock 72205, USA.
Reeves
W B
WB
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D004553:Electric Conductivity; D005905:Glyburide / Q000494:pharmacology*; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007425:Intracellular Membranes / Q000378:metabolism; D018374:LLC-PK1 Cells / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials; D015221:Potassium Channels / Q000187:drug effects* / Q000502:physiology; D013552:Swine
D015221:Potassium Channels; D000255:Adenosine Triphosphate; D006861:Hydrogen Peroxide; D005905:Glyburide