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

Konishi, T.; Hamrick, Philip E.; Walsh, Philip

doi:10.3109/00016487809124717

Cited by 199 publications

(59 citation statements)

References 19 publications

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“…Despite high levels of PMCA1 in the stria vascularis and interdental cells, abnormal localization of PMCA1 to hair cell apical surfaces, and the presence of PMCA4 in stereocilia, dfw 2J endolymph Ca 2+ concentrations are significantly lower than those of wild-type mice, suggesting that PMCA2 is necessary to maintain normal endolymph Ca 2+ levels. Thus, our findings indicate that, unlike potassium whose endolymph concentration is believed to be established by the stria vascularis (Konishi et al 1978;Wangemann et al 1995), Ca 2+ endolymph concentrations are maintained, at least in part, by inner and outer hair cells.…”

Section: Pmca2 and Endolymph Ca 2+mentioning

confidence: 84%

Low Endolymph Calcium Concentrations in deafwaddler2J Mice Suggest that PMCA2 Contributes to Endolymph Calcium Maintenance

Wood

Muchinsky

Filoteo

et al. 2004

JARO

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In vertebrates, transduction of sound into an electrochemical signal is carried out by hair cells that rely on calcium to perform specialized functions. The apical surfaces of hair cells are surrounded by endolymphatic fluid containing calcium at concentrations that must be maintained by active transport. The mechanism of this transport is unknown, but an ATPdependent pump is believed to participate. Mutation of the Atp2b2 gene that encodes plasma membrane calcium ATPase type 2 (PMCA2) produces the deaf, ataxic mouse: deafwaddler 2J (dfw 2J ). We hypothesized that PMCA2 might transport calcium into the endolymph and that dfw 2J mice would have low endolymph calcium concentrations, possibly contributing to their deafness and ataxia. First, using immunocytochemistry, we demonstrated that PMCA2 is present in control mice inner and outer hair cell stereocilia where it could pump calcium into the endolymph and that PMCA2 is absent in dfw 2J stereocilia. Second, using an aspirating microelectrode and calcium-sensitive fluorescent dye, we found that dfw 2J mice endolymph calcium concentrations are significantly lower than those of control mice. These findings suggest that PMCA2, located in hair cell stereocilia, contributes significantly to endolymph calcium maintenance.

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Section: Pmca2 and Endolymph Ca 2+mentioning

confidence: 84%

Low Endolymph Calcium Concentrations in deafwaddler2J Mice Suggest that PMCA2 Contributes to Endolymph Calcium Maintenance

Wood

Muchinsky

Filoteo

et al. 2004

JARO

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“…In this study, EP was measured at both the apical and basal turns, which correspond to low and high best frequencies, respectively. )EP was used as an indicator of hair cell function since )EP represents a fraction (voltage-divider) of the hair cell basolateral membrane voltage in scala media (Dallos 1996, Konishi et al 1967, 1978Marcus 1986;Syka et al 1981). …”

Section: Introductionmentioning

confidence: 99%

Age-Related Changes in Cochlear Endolymphatic Potassium and Potential in CD-1 and CBA/CaJ Mice

Marcus

2003

JARO - Journal of the Association for Research in Otolaryngolog

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The CD-1 mouse strain is known to have early onset of hearing loss that is progressive with aging. We sought to determine whether a disturbance of K + homeostasis and pathological changes in the cochlear lateral wall were involved in the age-related hearing loss (AHL) of CD-1 as compared to the CBA/CaJ strain which has minimal AHL. In the present study, the endocochlear potential (EP) and endolymphatic K + concentration ([K + ] e ) were measured in both strains of mice with double-barrel microelectrodes at ''young'' (1-2 mo) and ''old'' (5-9 mo) ages. CBA/ CaJ mice displayed no changes with aging in EP and [K + ] e of the basal turn. In the apical turn, there was a small positive shift of the EP (10 mV) with aging under both normoxic and acute anoxic conditions ()EP), without any change of [K + ] e . Further, there were no obvious pathological changes in the lateral wall of CBA/CaJ mice. By contrast, old CD-1 mice displayed a significantly reduced [K + ] e by 30% in both basal and apical turns with no significant changes in normoxic EP. The )EP in the apical turn was significantly reduced in magnitude by 6 mV. A severe loss of cells with aging was observed in the region of type IV fibrocytes of the apical and basal turns and of type II fibrocytes in the basal turn. A complete degeneration of organ of Corti was also observed at the basal turn of old CD-1 mice, as well as a basalward decline of spiral ganglion neuron density. The pathological changes in spiral ligament of CD-1 mice were similar to those of an inbred mouse strain C57BL/6J that expresses an AHL gene (ahl) and might be a primary etiology of AHL of CD-1 mice. These findings have ramifications for our understanding of AHL and for interpretation of genetic mutations in a CD-1 background.

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“…The stria vascularis is thought to secrete K + from perilymph into endolymph and to generate an EP of +80-90 mV (von Bekesy, 1950;Tasaki and Spyroupoulos, 1959;Konishi et al, 1978;Wangemann et al, 1995;Wangemann, 2002). The stria vascularis is a highly vascularized epithelium and part of the epithelial cellular sheet delineating the endolymph compartment.…”

mentioning

confidence: 99%

“…These fluids are amazingly different in their chemical composition: Perilymph resembles extracellular fluids in general (for reviews, see Wangemann and Schacht, 1996;Ferrary and Sterkers, 1998), but endolymph has the characteristics of an intracellular fluid in that it has high K + and low Na + concentrations (for a review, see Sterkers et al, 1988). Furthermore, the electrical potential of endolymph [endocochlear potential (EP)] is positive by ~80-90 mV relative to perilymph (Tasaki and Spyropoulos, 1959;Konishi et al, 1978). It is now widely accepted that these characteristics of endolymph (high K + concentration and EP) are indispensable for cochlear hair cells to transduce acoustic stimuli into electrical signals (for a review, see Hudspeth, 1989).…”

mentioning

confidence: 99%

Compartmentalization established by claudin-11-based tight junctions in stria vascularis is required for hearing through generation of endocochlear potential

Kitajiri

Miyamoto

Mineharu

et al. 2004

Journal of Cell Science

146

139

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Claudins are cell adhesion molecules working at tight junctions (TJs) that are directly involved in compartmentalization in multicellular organisms. The cochlea includes a rather peculiar compartment filled with endolymph. This compartment is characterized by high K+ concentration (∼150 mM) and a positive endocochlear potential (∼90 mV; EP), both indispensable conditions for cochlear hair cells to transduce acoustic stimuli to electrical signals. These conditions are thought to be generated by the stria vascularis, which is adjacent to the endolymph compartment. The stria vascularis itself constitutes an isolated compartment delineated by two epithelial barriers, marginal and basal cell layers. Because TJs of basal cells are primarily composed of claudin-11, claudin-11-deficient (Cld11-/-) mice were generated with an expectation that the compartmentalization in stria vascularis in these mice would be affected. Auditory brainstem response measurements revealed that Cld11-/- mice suffered from deafness; although no obvious gross morphological malformations were detected in Cld11-/- cochlea, freeze-fracture replica electron microscopy showed that TJs disappeared from basal cells of the stria vascularis. In good agreement with this, tracer experiments showed that the basal cell barrier was destroyed without affecting the marginal cell barrier. Importantly, in the endolymph compartment of Cld11-/- cochlea, the K+ concentration was maintained around the normal level (∼150 mM), whereas the EP was suppressed down to ∼30 mV. These findings indicated that the establishment of the stria vascularis compartment, especially the basal cell barrier, is indispensable for hearing ability through the generation/maintenance of EP but not of a high K+ concentration in the endolymph.

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

Cited by 199 publications

References 19 publications

Low Endolymph Calcium Concentrations in deafwaddler2J Mice Suggest that PMCA2 Contributes to Endolymph Calcium Maintenance

Low Endolymph Calcium Concentrations in deafwaddler2J Mice Suggest that PMCA2 Contributes to Endolymph Calcium Maintenance

Age-Related Changes in Cochlear Endolymphatic Potassium and Potential in CD-1 and CBA/CaJ Mice

Compartmentalization established by claudin-11-based tight junctions in stria vascularis is required for hearing through generation of endocochlear potential

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