A novel, volume-correlated Cl- conductance in marginal cells dissociated from the stria vascularis of gerbils

Using the whole-cell patch-clamp technique, we examined Cl--selective currents manifested by strial marginal cells isolated from the inner ear of gerbils. A large Cl--selective conductance of similar to 18 nS/pF was found from nonswollen cells in isotonic buffer containing 150 mM Cl-. Under a quasi-symmetrical Cl- condition, the 'instantaneous' current-voltage relation was close to linear, while the current-voltage relation obtained at the end of command pulses of duration 400 msec showed weak outward rectification. The permeability sequence for anionic currents was as SCN- > Br- congruent to Cl- > F- > NO3- congruent to I- > gluconate(-), corresponding to Eisenmann's sequence V. When whole-cell voltage clamped in isotonic bathing solutions, the cells exhibited volume changes that were accounted for by the Cl- currents driven by the imposed electrochemical potential gradients. The volume change was elicited by lowered extracellular Cl- concentration, anion substitution and altered holding potentials. The Cl- conductance varied in parallel with cell volume when challenged by bath anisotonicity. The whole-cell Cl- current was only partially blocked by both 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB, 0.5 mM) and diphenylamine-2-carboxylic acid (DPC, 1.0 mM), but 4-acetamido-4'-isothiocyanato-stilbene-2,2'-disulfonic acid (SITS, 0.5 mM) was without effect. The properties of the present whole-cell Cl- current resembled those of the single Cl- channel previously found in the basolateral membrane of the marginal cell (Takeuchi et al., Hearing Res. 83:89-100, 1995), suggesting that the volume-correlated Cl- conductance could be ascribed predominantly to the basolateral membrane. This Cl- conductance may function not only in cell volume regulation but also for the transport of Cl- and the setting of membrane potential in marginal cells under physiological conditions.