title: The gastric H,K-ATPase in stria vascularis contributes to pH regulation of cochlear endolymph but not to K secretion.
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.
authors: Department of Anatomy & Physiology, Cellular Biophysics Laboratory, Kansas State University, 228 Coles Hall, Manhattan, KS, 66506-5802, USA.|Deparment of Anatomy & Physiology, Cell Physiology Laboratory, Kansas State University, 228 Coles Hall, Manhattan, KS 66506-5802, USA.|Department of Otolaryngology-Head and Neck Surgery, Tohoku University Graduate School of Medicine, Sendai, 980-8574, Japan.
authors: Hiromitsu
authors: H
authors: Miyazaki
authors: Deparment of Anatomy & Physiology, Cell Physiology Laboratory, Kansas State University, 228 Coles Hall, Manhattan, KS 66506-5802, USA.
authors: Philine
authors: P
authors: Wangemann
authors: Department of Anatomy & Physiology, Cellular Biophysics Laboratory, Kansas State University, 228 Coles Hall, Manhattan, KS, 66506-5802, USA. marcus@ksu.edu.
authors: Daniel C
authors: DC
authors: Marcus
mesh_terms: D000136:Acid-Base Equilibrium; D000818:Animals; D004710:Endolymph / Q000378:metabolism*; D005260:Female; D017506:H(+)-K(+)-Exchanging ATPase / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D011188:Potassium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013316:Stria Vascularis / Q000201:enzymology / Q000378:metabolism*
chemical_list: D017506:H(+)-K(+)-Exchanging ATPase; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium
keywords: Acid–base balance; Endolymph; Hydrogen ion secretion; Inner ear; Ion-selective self-referencing electrode; Potassium secretion; Stria vascularis