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.

The expression of endothelin type A and B receptors in the lateral wall of the mouse cochlea

“…The cochlear lateral wall, consisting of the StV and adjacent NSt tissues, is bound by several kinds of parasensory epithelium. These parasensory epithelium cells play an important role in the active ion transportation of K + [18]. The strial vascularis is largely responsible for generating the high K + level in the endolymph, used by neurosensory cells for mechanoelectrical transduction.…”

Critical Roles of Transitional Cells and Na/K-ATPase in the Formation of Vestibular Endolymph

“…Moreover, [K ϩ ]ec is regulated by the same mechanisms controlling in vivo endolymph homeostasis (Wangemann, 1995(Wangemann, , 2002Lang et al, 2007): efflux through FM1.43-, gadolinium-, and aminoglycoside-sensitive channels (transduction channels), influx relying on ouabainand bumetanide-sensitive transporters (Na/K-ATPase and NKCC1), and KCNE1. However, experiments performed with cysts and P10 utricles underline the key role of Na/K-ATPase in endolymph formation as well as particular developmental functions of dark and transitional cells during endolymph maturation.…”

“…At their basolateral pole, these cells take up K ϩ by the Na/K-ATPase and Na-K-2Cl cotransporter 1 (NKCC1). K ϩ is then apically released into the endolymph through KCNE1/KCNQ1 channels and, presumably, other accessory K ϩ channels (Wangemann, 1995(Wangemann, , 2002Lang et al, 2007). The importance of such K ϩ cycling in endolymph maintenance is illustrated by the endolymph anomalies occurring in Menière's disease and Pendred syndromes, both of which comprise vestibular dysfunction among their symptoms.…”

Differences Between the Negatively Activating Potassium Conductances of Mammalian Cochlear and Vestibular Hair Cells

“…g K,n may also be an important part of an hypothetical K + recycling pathway within the cochlea. By this scheme, K + enters hair cells through mechanoelectrical transduction channels in the bundle, exits the hair cell via g K,n and other K + -selective channels located at the synaptic pole of the hair cell (Santos-Sacchi et al 1997), then travels through a system of gap junctions to the stria vascularis (reviewed in Santos-Sacchi 2000; Kikuchi et al 2000;Wangemann 2002).…”