title: Characterization of potassium permeability of cochlear duct by perilymphatic perfusion of barium.
abstract: The relative transepithelial "permeabilities" of the cochlear duct to K, Na, and Cl were investigated so as to identify the K-selective tissues and to determine the cellular origin of this selectivity. Single-ion substitutions were made for K, Na, and Cl with the impermeant species N-methyl-D-glucamine (NMDG) for K and Na and gluconate or sulfate for Cl in perilymph. Transepithelial potential changes were relatively slow and small for Na and Cl substitutions. However, either K for Na or K for NMDG substitutions demonstrated a pronounced K selectivity (rapid changes of electrical potential) of only the sensory-cell tissue (organ of Corti). The response to the K for Na substitution was most clearly seen after electrogenic K transport was inhibited by ischemia while the sensory cells were metabolically sustained via perilymphatic perfusion. Under this condition, perfusion of a medium containing 154 mM K gluconate reduced the negative potential (typically -25 to -40 mV) to within a few millivolts of zero. In a control medium, perilymphatic barium (0.5-5 mM) produced qualitatively similar effects, suggesting that this K selectivity is localized primarily at the basolateral membrane of the sensory cells rather than at the junctional complexes.
mesh_terms: D000818:Animals; D001464:Barium; D001485:Basement Membrane / Q000378:metabolism; D002463:Cell Membrane Permeability; D002712:Chlorides / Q000378:metabolism; D003051:Cochlea / Q000378:metabolism*; D003053:Cochlear Duct / Q000378:metabolism*; D003055:Cochlear Microphonic Potentials; D006168:Guinea Pigs; D007473:Ion Channels / Q000378:metabolism*; D008536:Meglumine; D010477:Perfusion; D010498:Perilymph / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism
chemical_list: D002712:Chlorides; D007473:Ion Channels; D001464:Barium; D008536:Meglumine; D012964:Sodium; D011188:Potassium