Acidity in the Endolymphatic Sac Fluid of Guinea Pigs

Tsujikawa, Satoshi; Yamashita, Toshio; Amano, Hajime; Kumazawa, Tadami; Vosteen, K. H.

doi:10.1159/000276298

Cited by 13 publications

(10 citation statements)

References 14 publications

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“…The endolymph of the cochlea and vestibular end-organ is potassium-rich and sodiumpoor, whereas the luminal content of the endolymphatic sac is sodium-rich and potassium-poor (Morgenstern 1985;Silverstein and Schuknecht 1966). The latter fluid has a pH of 6.65 in the guinea pig (Tsujikawa et al 1992). Perhaps the function of pendrin in the endolymphatic sac is to maintain the ionic and/or pH homeostasis between these two compositionally distinct fluids.…”

Section: Discussionmentioning

confidence: 99%

Localization and Functional Studies of Pendrin in the Mouse Inner Ear Provide Insight About the Etiology of Deafness in Pendred Syndrome

Royaux

Belyantseva

et al. 2003

JARO - Journal of the Association for Research in Otolaryngolog

140

149

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Immunolocalization studies of mouse cochlea and vestibular end-organ were performed to study the expression pattern of pendrin, the protein encoded by the Pendred syndrome gene (PDS), in the inner ear. The protein was restricted to the areas composed of specialized epithelial cells thought to play a key role in regulating the composition and resorption of endolymph. In the cochlea, pendrin was abundant in the apical membrane of cells in the spiral prominence and outer sulcus cells (along with their root processes). In the vestibular end-organ, pendrin was found in the transitional cells of the cristae ampullaris, utriculi, and sacculi as well as in the apical membrane of cells in the endolymphatic sac. Pdsknockout (Pds )/) ) mice were found to lack pendrin immunoreactivity in all of these locations. Histological studies revealed that the stria vascularis in Pds )/) mice was only two-thirds the thickness seen in wildtype mice, with the strial marginal cells showing irregular shapes and sizes. Functional studies were also performed to examine the role of pendrin in endolymph homeostasis. Using double-barreled electrodes placed in both the cochlea and the utricle, the endocochlear potential and endolymph potassium concentration were measured in wild-type and Pdsmice. Consistent with the altered strial morphology, the endocochlear potential in Pds )/) mice was near zero and did not change during anoxia. On the other hand, the endolymphatic potassium concentration in Pds )/) mice was near normal in the cochlea and utricle. Together, these results suggest that pendrin serves a key role in the functioning of the basal and/ or intermediate cells of the stria vascularis to maintain the endocochlear potential, but not in the potassium secretory function of the marginal cells.

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Section: Discussionmentioning

confidence: 99%

Localization and Functional Studies of Pendrin in the Mouse Inner Ear Provide Insight About the Etiology of Deafness in Pendred Syndrome

Royaux

Belyantseva

et al. 2003

JARO - Journal of the Association for Research in Otolaryngolog

140

149

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“…In the cochlea and utricle, the endolymphatic pH is slightly alkaline (pH 7.5) (93,180,315). In the endolymphatic sac, on the other hand, the pH is more acidic (pH 6.6 -7.1) (35,281). The functional significance of these differences is largely elusive.…”

Section: Ph Homeostasismentioning

confidence: 99%

Functional significance of channels and transporters expressed in the inner ear and kidney

Läng

Vallon²,

Knipper³

et al. 2007

American Journal of Physiology-Cell Physiology

203

180

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A number of ion channels and transporters are expressed in both the inner ear and kidney. In the inner ear, K(+) cycling and endolymphatic K(+), Na(+), Ca(2+), and pH homeostasis are critical for normal organ function. Ion channels and transporters involved in K(+) cycling include K(+) channels, Na(+)-2Cl(-)-K(+) cotransporter, Na(+)/K(+)-ATPase, Cl(-) channels, connexins, and K(+)/Cl(-) cotransporters. Furthermore, endolymphatic Na(+) and Ca(2+) homeostasis depends on Ca(2+)-ATPase, Ca(2+) channels, Na(+) channels, and a purinergic receptor channel. Endolymphatic pH homeostasis involves H(+)-ATPase and Cl(-)/HCO(3)(-) exchangers including pendrin. Defective connexins (GJB2 and GJB6), pendrin (SLC26A4), K(+) channels (KCNJ10, KCNQ1, KCNE1, and KCNMA1), Na(+)-2Cl(-)-K(+) cotransporter (SLC12A2), K(+)/Cl(-) cotransporters (KCC3 and KCC4), Cl(-) channels (BSND and CLCNKA + CLCNKB), and H(+)-ATPase (ATP6V1B1 and ATPV0A4) cause hearing loss. All these channels and transporters are also expressed in the kidney and support renal tubular transport or signaling. The hearing loss may thus be paralleled by various renal phenotypes including a subtle decrease of proximal Na(+)-coupled transport (KCNE1/KCNQ1), impaired K(+) secretion (KCNMA1), limited HCO(3)(-) elimination (SLC26A4), NaCl wasting (BSND and CLCNKB), renal tubular acidosis (ATP6V1B1, ATPV0A4, and KCC4), or impaired urinary concentration (CLCNKA). Thus, defects of channels and transporters expressed in the kidney and inner ear result in simultaneous dysfunctions of these seemingly unrelated organs.

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“…ES epithelial cells are strong candidate for regulator of endolymphatic pH because of their strong immunoreactivity for the proteins such as H + ‐ATPase and anion exchangers [Stanković et al, 1997]. Especially, the pH of the ES endolymph is relatively acidic than those of cochlear and vestibular endolymph [Tsujikawa et al, 1992], which indicates that ES epithelial cells have specific pH regulatory system. However, the exact mechanism of maintaining acidic pH of the endolymph in ES is unclear.…”

mentioning

confidence: 99%

Interferon‐γ suppresses Na⁺–H⁺ exchanger in cultured human endolymphatic sac epithelial cells

Son

Moon

Kim

et al. 2009

J of Cellular Biochemistry

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Adequate regulation of endolymphatic pH is essential for maintaining inner ear function. The Na(+)-H(+) exchanger (NHE) is a major determinant of intracellular pH (pH(i)), and facilitates Na(+) and fluid absorption in various epithelia. We determined the functional and molecular expression of NHEs in cultured human endolymphatic sac (ES) epithelial cells and examined the effect of IFN-gamma on NHE function. Serial cultures of human ES epithelial cells were generated from tissue samples. The molecular expression of NHE1, -2, and -3 isoforms was determined by real-time RT-PCR. The functional activity of NHE isoforms was measured microfluorometrically using a pH-sensitive fluorescent dye, 2',7'-bis(carbonylethyl)-5(6)-carboxyfluorescein (BCECF), and a NHE-inhibitor, 3-methylsulfonyl-4-piperidinobenzoyl guanidine methanesulfonate (HOE694). NHE1, -2, and -3 mRNAs were expressed in human ES epithelial cells. Functional activity of NHE1 and -2 was confirmed in the luminal membrane of ES epithelial cells by sequentially suppressing Na(+)-dependent pH(i) recovery from intracellular acidification using different concentrations of HOE694. Treatment with IFN-gamma (50 nM for 24 h) suppressed mRNA expression of NHE1 and -2. IFN-gamma also suppressed functional activity of both NHE1 and -2 in the luminal membrane of ES epithelial cells. This study shows that NHEs are expressed in cultured human ES epithelial cells and that treatment with IFN-gamma suppresses the expression and functional activity of NHE1 and -2.

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Acidity in the Endolymphatic Sac Fluid of Guinea Pigs

Cited by 13 publications

References 14 publications

Localization and Functional Studies of Pendrin in the Mouse Inner Ear Provide Insight About the Etiology of Deafness in Pendred Syndrome

Localization and Functional Studies of Pendrin in the Mouse Inner Ear Provide Insight About the Etiology of Deafness in Pendred Syndrome

Functional significance of channels and transporters expressed in the inner ear and kidney

Interferon‐γ suppresses Na⁺–H⁺ exchanger in cultured human endolymphatic sac epithelial cells

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Acidity in the Endolymphatic Sac Fluid of Guinea Pigs

Cited by 13 publications

References 14 publications

Localization and Functional Studies of Pendrin in the Mouse Inner Ear Provide Insight About the Etiology of Deafness in Pendred Syndrome

Localization and Functional Studies of Pendrin in the Mouse Inner Ear Provide Insight About the Etiology of Deafness in Pendred Syndrome

Functional significance of channels and transporters expressed in the inner ear and kidney

Interferon‐γ suppresses Na+–H+ exchanger in cultured human endolymphatic sac epithelial cells

Contact Info

Product

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Interferon‐γ suppresses Na⁺–H⁺ exchanger in cultured human endolymphatic sac epithelial cells