[Effect of hydrogen peroxide on electric current of large-conductance calcium-activated potassium channel in isolated outer hair cells of old guinea pig cochlea].

The present study was aimed to investigate the effect of hydrogen peroxide (H2O2, oxygen free radical donator) on the current of large-conductance calcium-activated potassium channels (BK(Ca) channels) in isolated outer hair cells of old guinea pig cochlea, and to explore the underlying mechanism. Outer hair cells of old guinea pig cochlea were acutely enzyme-isolated, and currents were recorded by whole-cell patch clamp. The results showed that, rapid activation and non-deactivation electric currents with a string of large amplitude were recorded. Activation voltage of the current was above -40 - -30 mV. The amplitude of current was increased continuously with the rising of membrane potential. The current showed characteristics of outward rectification without "rundown" phenomenon. IbTX (100 nmol/L) could completely block the activity of channel, which confirmed BK(Ca) channel's current. BK(Ca) current amplitude and peak current density increased with the increment of H2O2 concentration (1, 2, 4 µmol/L), showing concentration-dependent activation by H2O2. Our results suggest that oxygen free radical/BK(Ca) pathway may be able to adjust the balance of intracellular calcium in outer hair cells.