The mechanism underlying maintenance of the endocochlear potential by the K+ transport system in fibrocytes of the inner ear

•  The endocochlear potential (EP) of +80 mV in cochlear endolymph is essential for audition and controlled by K+ transport across the lateral cochlear wall composed of two epithelial barrier layers, the syncytium containing the fibrocytes and the marginal cells. •  The EP depends upon the diffusion potential elicited by a large K+ gradient across the apical surface of the syncytium. •  We examined by electrophysiological approaches an involvement of Na+,K+‐ATPase, which occurs at the syncytium's basolateral surface comprising the fibrocytes’ membranes and would mediate K+ transport across the lateral wall, in maintenance of the EP. •  We show that the Na+,K+‐ATPase sustains the syncytium's high [K+] that is crucial for the K+ gradient across the apical surface of the syncytium. •  The results help us better understand the mechanism underlying the establishment of the EP as well as the pathophysiological process for deafness induced by dysfunction of the ion transport apparatus.

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