Figure 1. Effect of bicarbonate in isolated guinea-pig OHCs.

A, extracellular chloride and bicarbonate affect OHC pH_i and length. The starting solution was buffered by 10 mm Hepes and 25 mm HCO₃⁻ replacement introduced by superfusion of the bath. The introduction of bicarbonate led to a transient acidification (shown by the change in the BCECF fluorescence ratio) followed by recovery on bicarbonate loading. The slope of this recovery (shown as a dashed line (a)) is to be compared with the slope (shown as dashed line (b)) estimated for OHCs exposed to 25 mm HCO₃⁻ in 150 mm Cl_o⁻ (reported by Ikeda et al. 1992, Fig. 11 and converted to a ratio as in Tunstall et al. 1995). On removal of bicarbonate the pH overshot the baseline. There was a transient OHC shortening on first moving to low Cl_o shown at 280 s. The cells recovered to a steady length with a small increase in length, L, during HCO₃⁻ application. B, frames showing an OHC loaded with BCECF, monitored during bath solution exchange at time points t= 0 and t= 280 s. Widefield fluorescent microscopy.