K+ Cycling and Its Regulation in the Cochlea and the Vestibular Labyrinth

Abstract

Potassium (K+) plays a very important role in the cochlea. K+ is the major cation in endolymph and the charge carrier for sensory transduction and the generation of the endocochlear potential. The importance of K+ handling in the cochlea is marked by the discovery of several forms of hereditary deafness that are due to mutations of K+ channels. Deafness results from mutations of KCNQ4, a K+ channel in the sensory hair cells, as well as from mutations of the gap junction proteins GJB2, GJB3 and GJB6 that may facilitate cell-to-cell movements of K+. Deafness results also from mutations of KCNQ1 or KCNE1, subunits of a K+ channel that carries K+ from strial marginal cells and vestibular dark cells into endolymph. Further, deafness results from mutations of KCNJ10, a K+ channel that generates the endocochlear potential in conjunction with the high K+ concentration in strial intermediate cells and the low K+ concentration in the intrastrial fluid spaces. This review details recent advances in the understanding of K+ transport and its regulation in the cochlea and the vestibular labyrinth.