Key words: Chloride conductance — Cell volume — Marginal cell — Endolymph — Inner ear
Springer Online Journal Archives 1860-2000
Chemistry and Pharmacology
Abstract. 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 ∼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−≅ Cl− 〉 F− 〉 NO− 3≅ 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.
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