Hydrogen Peroxide Inhibits Gap Junctional Coupling and Modulates Intracellular Free Calcium in Cochlear Hensen Cells
- 60 Downloads
The double whole-cell patch-clamp configuration was applied to analyze gap junctional conductance (G j ) of isolated pairs of cochlear supporting Hensen cells of guinea pig under control conditions and in the presence of hydrogen peroxide (H2O2). Under control conditions, the dependence of G j on transjunctional voltage (V j ) appeared to vary between different cell pairs with a maximum value of about 40 nS at V j close to 0 mV. The voltage dependence and the maximum amplitude of G j stayed constant for at least 2 hr. Addition of H2O2 to the bath at concentrations above 0.08 mm caused a significant decrease of G j , but the membrane potential of about −30 mV was not affected. In parallel, intracellular free calcium ([Ca2+]i) was followed using fura-2. At 0.8 mm H2O2, a sustained increase of [Ca2+]i was observed, while 0.08 mm H2O2 evoked an oscillating-like behavior of [Ca2+]i. We propose that the H2O2-evoked inhibition of gap junctional coupling of Hensen cells is closely related to pathophysiological conditions such as noise- induced hearing loss, aminoglycoside-related ototoxicity and presbycusis, which are known to be associated with production of free radicals.
Unable to display preview. Download preview PDF.