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-PK 1 cell line. Exposure of cells to H 2 O 2 (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 H 2 O 2 -induced cellular hyperpolarization. H 2 O 2 (5 mM) produced a sixfold increase in the whole cell conductance. The reversal potential ofthe H 2 O 2 -induced current was consistent with a K + -selective conductance. This current was blocked almost completely by 5 mM barium and 500 μM glibenclamide but only partially by 15 mM tetraethylammonium. Exposure of LLC-PK 1 cells to 5 mM H 2 O 2 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 H 2 O 2 -induced activation of the K + conductance. These findings indicate that H 2 O 2 activates an ATP-sensitive, Ca 2+ -independent K + conductance in LLC-PK 1 cells.