title: Involvement of Na(+)-H+ exchange in intracellular pH recovery from acid load in the stria vascularis of the guinea-pig cochlea.
abstract: The effect of acid load by NH4+ prepulse method on intracellular pH (pHi) and Na concentration ([Na+]i) in the stria vascularis tissue was studied using fluorescence ratio image microscopy. The pHi and [Na+]i were determined with fluorescence indicator dyes, 2',7'-bis(2-carboxyethyl)-5,6-carboxyfluorescein and sodium-binding benzofuran isophthalate, respectively. Intracellular acidification from the basal pHi of 7.12 +/- 0.08 to 6.82 +/- 0.08 was induced by NH4+ prepulse. Subsequent addition to the standard NaCl solution gradually increased pHi to the control value. This Na(+)-induced pHi recovery was significantly inhibited by the presence of amiloride and absence of external Na+. Basal free [Na+]i was 19 +/- 5 mM in the stria vascularis. In the same maneuver of acid load, the pHi recovery was associated with the increase in [Na+]i sensitive to the amiloride derivative. Thus, the process of the pHi recovery from acid load was demonstrated to involve the Na(+)-H+ exchange in the stria vascularis.
authors.affiliation: Department of Otolaryngology, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Ikeda
authors.forename: H
authors.initials: H
authors.lastname: Sunose
authors.forename: T
authors.initials: T
authors.lastname: Takasaka
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000643:Ammonium Chloride / Q000494:pharmacology*; D000818:Animals; D003592:Cytophotometry; D003593:Cytoplasm / Q000378:metabolism; D005453:Fluorescence; D006168:Guinea Pigs; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008536:Meglumine / Q000494:pharmacology; D010498:Perilymph / Q000187:drug effects / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology; D013316:Stria Vascularis / Q000187:drug effects* / Q000378:metabolism*
chemical_list: D000644:Quaternary Ammonium Compounds; D000643:Ammonium Chloride; D012965:Sodium Chloride; D008536:Meglumine; D000584:Amiloride; D006859:Hydrogen; D012964:Sodium