T-butyl hydrogen peroxide increases the activities of the Maxi-K channels of rat brain

In this study, we investigated the effects of tertiary-butyl hydrogen perox ide (tBHP) on the large-conductance Ca2+-activated K+ (Maxi-K) channel of r at brain using lipid bilayer. When tBHP was applied to the cytosolic side, the open probability (Po) of both fast- and slow-gating Maxi-K channels inc reased within 1 min in dose-dependent manner. tBHP effects did not reverse immediately, suggesting tBHP induces some chemical modification on the chan nel protein. From kinetic analysis of single channel data, the increase in the Po appears to be mainly due to shortening of closed dwell time in both types of the Maxi-K channels. 50 mu M diamide, a sulfhydryl-specific oxidan t, irreversibly decreased the Po. However, further addition of 7.3 mM tBHP still increased the Po, suggesting that tBHP does not share the target for oxidation with diamide. (C) 2000 Elsevier Science Inc. All rights reserved.