Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2016 Aug 11;17(1):1.
doi: 10.1186/s12899-016-0024-1.

The Gastric H,K-ATPase in Stria Vascularis Contributes to pH Regulation of Cochlear Endolymph but Not to K Secretion

Affiliations
Free PMC article

The Gastric H,K-ATPase in Stria Vascularis Contributes to pH Regulation of Cochlear Endolymph but Not to K Secretion

Hiromitsu Miyazaki et al. BMC Physiol. .
Free PMC article

Abstract

Background: Disturbance of acid-base balance in the inner ear is known to be associated with hearing loss in a number of conditions including genetic mutations and pharmacologic interventions. Several previous physiologic and immunohistochemical observations lead to proposals of the involvement of acid-base transporters in stria vascularis.

Results: We directly measured acid flux in vitro from the apical side of isolated stria vascularis from adult C57Bl/6 mice with a novel constant-perfusion pH-selective self-referencing probe. Acid efflux that depended on metabolism and ion transport was observed from the apical side of stria vascularis. The acid flux was decreased to about 40 % of control by removal of the metabolic substrate (glucose-free) and by inhibition of the sodium pump (ouabain). The flux was also decreased a) by inhibition of Na,H-exchangers by amiloride, dimethylamiloride (DMA), S3226 and Hoe694, b) by inhibition of Na,2Cl,K-cotransporter (NKCC1) by bumetanide, and c) by the likely inhibition of HCO3/anion exchange by DIDS. By contrast, the acid flux was increased by inhibition of gastric H,K-ATPase (SCH28080) but was not affected by an inhibitor of vH-ATPase (bafilomycin). K flux from stria vascularis was reduced less than 5 % by SCH28080.

Conclusions: These observations suggest that stria vascularis may be an important site of control of cochlear acid-base balance and demonstrate a functional role of several acid-base transporters in stria vascularis, including basolateral H,K-ATPase and apical Na,H-exchange. Previous suggestions that H secretion is mediated by an apical vH-ATPase and that basolateral H,K-ATPase contributes importantly to K secretion in stria vascularis are not supported. These results advance our understanding of inner ear acid-base balance and provide a stronger basis to interpret the etiology of genetic and pharmacologic cochlear dysfunctions that are influenced by endolymphatic pH.

Keywords: Acid–base balance; Endolymph; Hydrogen ion secretion; Inner ear; Ion-selective self-referencing electrode; Potassium secretion; Stria vascularis.

Figures

Fig. 1
Fig. 1
Self-referencing ion-selective electrode method. The electrode (probe) tip oscillates a distance of about 30 μm (double-headed arrow). The mean position is first set remote from the source (about 500 μm away; not shown) and the difference signal from the oscillation is taken as zero. The oscillating probe is then set within several μm of the a artificial source or b epithelium, and the difference signal in the concentration gradient is taken as a relative measure of the ion flux. Changes in ion flux are monitored during bath perfusion of control and experimental solutions. (Top panels) diagram; (Bottom panels) photomicrographs of artificial and epithelial sources and adjacent probe. Liquid ion exchanger (selective for K+ or H+) is visible in the tip of the electrode
Fig. 2
Fig. 2
H+-flux from stria vascularis; control, glucose-free, ouabain and bafilomycin. a Summary traces (N = 4) of time-controls during perfusion of control bath solution in the absence of any experimental agents. Boxes labeled C1 and C2 are the perfusion times from two separate reservoirs of bath solution (see Methods for composition). b Summary traces (N = 3) of glucose-free (0-glucose) perfusion. c Summary traces (N = 3) of ouabain (1 mM) perfusion. d Bar graphs of steady state effects of time-control, glucose-free, ouabain and bafilomycin (1 μM; N = 6) perfusion. *, P < 0.05; ns, not significant. a, b, c Traces are the vertical averages of N experiments conducted with identical time-course. Standard error bars are indicated only at intervals for clarity; boxes show duration of the experimental period
Fig. 3
Fig. 3
K+- and H+- fluxes from stria vascularis; bumetanide and DIDS. a and c K+ flux; b and d H+ flux. a Summary traces (N = 7) of effect of perfusion of bumetanide (50 μM; bumet) on K+ flux from stria vascularis. b Summary traces (N = 6) of effect of perfusion of bumetanide (50 μM) on H+ flux from stria vascularis. c Concentration-response curve for bumetanide on K+ flux from stria vascularis fit by the Michaelis-Menton equation (N = 5–6). d Bar graph summaries of steady–state effects of bumetanide (50 μM; N = 6; Bumet) and DIDS (1 mM; N = 6) on H+ flux from stria vascularis. *, P < 0.05; ns, not significant. a, b: boxes show duration of the experimental period
Fig. 4
Fig. 4
Inhibition by amiloride analogs of strial H+ flux from stria vascularis. a Summary traces of perfusion of dimethylamiloride (DMA; 30 μM; N = 5); box shows the duration of the experimental period. b summary family of curves for four Na+,H+ exchanger inhibitors: HOE694 (N = 3–7), amiloride (N = 4–6), S3226 (N = 3–6) and DMA (N = 3–9). Data from DMA and S3226 were fitted with a dual Michaelis-Menton equation consisting of one component that contributes 18 % (putative apical NHEs) and a second component that contributes 82 % (putative metabolic pathway target) of the total response
Fig. 5
Fig. 5
Effects of inhibition of gastric H+,K+-ATPase on H+- and K+-fluxes from stria vascularis. a Summary traces (N = 7) of effect on H+ flux of perfusion of SCH28080 (10 nM). Box shows the duration of the experimental period. b Concentration-response curve (N = 3–7) for stimulation of strial H+-flux by SCH28080. Data fit by the Michaelis-Menton equation. c Small inhibition of K+ flux from stria vascularis by SCH28080 (10 nM; N = 7)) and absence of effect (SCH, SCH28080) after inhibition of K+ flux by bumetanide (200 μM; N = 6; bumet). *, P < 0.05; ns, not significant
Fig. 6
Fig. 6
Cell model of H+ and K+ secretion by strial marginal cells in the cochlea. Transepithelial secretion of K+ is mediated by uptake of K+ from the basolateral side of the strial marginal cells (SMC) via the Na+,K+-ATPase and the Na+,2Cl,K+-cotransporter (NKCC1). The contribution to K+ flux by the gastric H+,K+-ATPase is minimal. K+ transport from the cytosol into endolymph is mediated by KCNQ1/KCNE1 K+ channels in the apical membrane. Metabolically-generated acid exits the cell via the basolateral gastric H+,K+-ATPase and the apical Na+,H+-exchangers. Apical membrane H+ exit is increased when the basolateral H+,K+-ATPase is inhibited and the H+ flux re-routed to the apical membrane. Cl that was taken up into the cytosol via the Na+,2Cl,K+-cotransporter is recycled across the basolateral membrane via the ClC-K/barttin Cl channels. Additional putative acid/base transporters, such as basolateral DIDS-sensitive HCO3 efflux via NBCe1, are not shown

Similar articles

See all similar articles

Cited by 2 articles

References

    1. Everett LA, Glaser B, Beck JC, Idol JR, Buchs A, Heyman M, Adawi F, Hazani E, Nassir E, Baxevanis AD, Sheffield VC, Green ED. Pendred syndrome is caused by mutations in a putative sulphate transporter gene (PDS) Nat Genet. 1997;17:411–22. doi: 10.1038/ng1297-411. - DOI - PubMed
    1. Wangemann P, Nakaya K, Wu T, Maganti RJ, Itza EM, Sanneman JD, Harbidge DG, Billings S, Marcus DC. Loss of cochlear HCO3− secretion causes deafness via endolymphatic acidification and inhibition of Ca2+ reabsorption in a Pendred syndrome mouse model. Am J Physiol Renal Physiol. 2007;292:F1345–53. doi: 10.1152/ajprenal.00487.2006. - DOI - PMC - PubMed
    1. Karet FE, Finberg KE, Nelson RD, Nayir A, Mocan H, Sanjad SA, Rodriguez-Soriano J, Santos F, Cremers CW, Di Pietro A, Hoffbrand BI, Winiarski J, Bakkaloglu A, Ozen S, Dusunsel R, Goodyer P, Hulton SA, Wu DK, Skvorak AB, Morton CC, Cunningham MJ, Jha V, Lifton RP. Mutations in the gene encoding B1 subunit of H+-ATPase cause renal tubular acidosis with sensorineural deafness. Nat Genet. 1999;21:84–90. doi: 10.1038/5022. - DOI - PubMed
    1. Stover EH, Borthwick KJ, Bavalia C, Eady N, Fritz DM, Rungroj N, Giersch AB, Morton CC, Axon PR, Akil I, Al-Sabban EA, Baguley DM, Bianca S, Bakkaloglu A, Bircan Z, Chauveau D, Clermont MJ, Guala A, Hulton SA, Kroes H, Li VG, Mir S, Mocan H, Nayir A, Ozen S, Rodriguez-Soriano J, Sanjad SA, Tasic V, Taylor CM, Topaloglu R, Smith AN, Karet FE. Novel ATP6V1B1 and ATP6V0A4 mutations in autosomal recessive distal renal tubular acidosis with new evidence for hearing loss. J Med Genet. 2002;39:796–803. doi: 10.1136/jmg.39.11.796. - DOI - PMC - PubMed
    1. Ikeda K, Morizono T. The preparation of acetic acid for use in otic drops and its effect on endocochlear potential and pH in inner ear fluid. Am J Otolaryngol. 1989;10:382–5. doi: 10.1016/0196-0709(89)90032-X. - DOI - PubMed

Substances

Feedback