LUMINAL NONSELECTIVE CATION AND OUTWARDLY RECTIFYING CHLORIDE CHANNELS IN CULTURED STRIAL MARGINAL CELLS FROM GERBIL

Ionic channels located on the luminal side of strial marginal cells (M Cs) of gerbil in culture were investigated using the patch-clamp techn ique. Two types of channels were identified. The most frequently recor ded single-channel activity corresponded to a non-selective cation (NS C) channel with a conductance of 23.7 +/- 0.2 pS (n = 18) in symmetric al NaCl conditions. The channel was activated by internal Ca2+ and inh ibited by internal adenine nucleotides and flufenamic acid. Spontaneou s activity of NSC channels was found in 16% of the cell-attached patch es and with a very high density (9 +/- 2 levels/patch, n = 28) in 100% of the excised patches. An outwardly rectifying chloride (ORC) channe l was also identified in 14% of the patches but only after excision. T he channel exhibited at 0 mV a unit conductance of 26.8 +/- 1.3 pS (n = 8) and a strong outward rectification in symmetrical NaCl conditions , and the open probability increased with depolarization. The luminal NSC channel and the ORC channel evidenced in this study might particip ate in the production of endolymph. Although extrapolation of the pres ents results to the in vivo situation should be made with caution, thi s study suggests that culture of strial MCs may be a suitable model fo r investigation of endolymph physiology.