Two types of K+ currents in marginal cells cultured from rat stria vascularis.
Membrane currents in marginal cells cultured from rat stria vascularis were studied using the whole-cell patch-clamp technique. Two types of voltage-dependent whole-cell currents were observed in the voltage range from -150 mV to +50 mV: an outwardly rectifying current and an inwardly rectifying current. The outwardly rectifying current, which was activated by depolarizing pulses more positive than -30 mV, was sensitive to TEA (20 mM) and relatively not to Ba2+ (0.5 mM). Tail current analysis revealed that the outward currents were primarily K+-selective. The conductance of the current was half-maximal at 0.5 mV and a substantial portion of current was not inactivated by the depolarizing prepulses from -30 mV to +20 mV. The inwardly rectifying current with rapid exponential activation was observed with hyperpolarizing voltage pulses. The zero-current potential of this current was dependent on extracellular K+ concentration. In contrast to the outwardly rectifying current, this current was blocked by extracellular application of Ba2+, not by TEA. The conductance of this current increased with the increase in external K+ concentration. Our data suggest that marginal cells cultured from rat stria vascularis express at least two types of voltage-dependent K+ currents which may serve as K+ secretory pathways into endolymph.
Kim
S J
SJ
Department of Physiology and Biophysics, Seoul National University College of Medicine, South Korea. sangjkim@plaza.snu.ac.kr
Juhn
S K
SK
D000818:Animals; D002478:Cells, Cultured; D004710:Endolymph / Q000378:metabolism; D005071:Evoked Potentials; D017136:Ion Transport / Q000187:drug effects; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D011188:Potassium / Q000378:metabolism* / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism; D051381:Rats; D013316:Stria Vascularis / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D019789:Tetraethylammonium / Q000494:pharmacology
D015221:Potassium Channels; D019789:Tetraethylammonium; D011188:Potassium