The endocochlear potential depends on two K ⁺ diffusion potentials and an electrical barrier in the stria vascularis of the inner ear

Abstract

hearing ͉ ion transport ͉ potassium

Development of the stria vascularis and potassium regulation in the human fetal cochlea: Insights into hereditary sensorineural hearing loss

“…The location of these proteins along the membranes of the different cells of the adult stria vascularis is depicted in Figure 1(B). Disrupting the function of any of these proteins (including connexin proteins) in the stria vascularis or at other locations in the cochlea where they are thought to be involved in K + homeostasis results in immediate SNHL (Cohen‐Salmon et al, 2002; Teubner et al, 2003; Nin et al, 2008). In many cases of both syndromic (as mentioned above) and nonsyndromic SNHL, the endocochlear potential is likely to be affected.…”

“…On the basolateral membranes of the marginal cells, K + uptake from the intrastrial space (the narrow fluid‐containing space between the marginal cells and the melanocytes) is mediated by the sodium‐potassium pump Na + /K + ‐ATPase (Schulte and Adams, 1989) and the Na + 2Cl ‐ K + cotransporter. Na + /K + ‐ATPase is known to be expressed in the adult human stria vascularis (Weber et al, 2001) and inhibition of Na + /K + ‐ATPase directly suppresses the endocochlear potential in guinea pigs (Kuijpers and Bonting, 1970; Nin et al, 2008). We found first expression of KCNQ1 on the luminal membranes of the marginal cells at W16.…”

“…In contrast to the potassium channels of the marginal cells, we did not observe any KCNJ10 expression in strial melanocytes up to the last stage we investigated, W18. As inhibition of this receptor directly suppresses the endocochlear potential (Nin et al, 2008), it is likely that the endocochlear potential is not yet generated at this stage. KCNJ10 is implicated in multiple syndromic disorders with SNHL.…”

The Membrane Properties of Cochlear Root Cells are Consistent with Roles in Potassium Recirculation and Spatial Buffering

“…This maintenance ensures the longevity of sensory hair cells and the generation of the endocochlear potential. The ion transporting mechanisms that regulate these concentrations have been characterized in a number of cochlear tissues, leading to widely held hypotheses of K + "recirculation" and "spatial buffering" (Forge et al 2003a;Hibino and Kurachi 2006;Kikuchi et al 2000;Kikuchi et al 1995;Nickel and Forge 2008;Nin et al 2008;Spicer and Schulte 1996;Takeuchi et al 2000;Wangemann 2006;Weber et al 2001;. In common with these mechanisms studied in the CNS and retina (Kofuji and Newman 2004), cochlear K + recirculation and spatial buffering both rely on gap junctional coupling throughout the epithelial cell network, and the ability of cells at the edges of the network to secrete K + .…”

“…The ionic composition of endolymph and the magnitude of the endocochlear potential (EP) in scala media are both regulated by stria vascularis (Nin et al 2008;Souter and Forge 1998). Experimental evidence from in vivo studies has suggested that K + in endolymph is sourced from perilymph, rather than from the blood supply (Wada et al 1979).…”