Ion Transport in Guinea Pig Cochlea:I. Potassium and Sodium Transport

The scala vestibuli and/or tympani in anesthetized guinea pigs was perfused with artificial perilymph containing 42K and 22Na for periods ranging from 5 to 60 minutes. Sound-evoked responses were recorded during the perfusion. The activities of 42K and 22Na in perilymph and endolymph were determined with a germanium detector in conjunction with a multichannel analyser. The perfusion of scala vestibuli and/or tympani did not result in appreciable changes in electrical responses. The introduction of 42K and 22Na into the scala tympani resulted in the rapid appearance of these radioisotopes in perilymph of the scala vestibuli. The activities of 42K and 22Na in perilymph of the scala tympani remained low with perfusion of scala vestibuli. This is in agreement with our Findings that the clearance of these radioisotopes was faster in scala tympani than in scala vestibuli. Our results further indicate that the endolymph took up 42K and extruded 22Na against the concentration gradients. The transport of 42K and 22Na across the cochlear partition was inhibited by anoxia or local application of ouabain. Uptake of 42K in the endolymph from perilymph of the scala vestibuli was comparable to uptake from perilymph of the scala tympani. These results suggest that +K is actively transported from perilymph to endolymph and +Na is extruded from endolymph to perilymph and that the active transport of +K takes place in the stria vascularis. By adopting a two-compartment system, the transport rate constant of +K was computed from our experimental data.