title: Mechanism of acid adaptation of a fish living in a pH 3.5 lake.
abstract: Despite unfavorable conditions, a single species of fish, Osorezan dace, lives in an extremely acidic lake (pH 3.5) in Osorezan, Aomori, Japan. Physiological studies have established that this fish is able to prevent acidification of its plasma and loss of Na(+). Here we show that these abilities are mainly attributable to the chloride cells of the gill, which are arranged in a follicular structure and contain high concentrations of Na(+)-K(+)-ATPase, carbonic anhydrase II, type 3 Na(+)/H(+) exchanger (NHE3), type 1 Na(+)-HCO(3)(-) cotransporter, and aquaporin-3, all of which are upregulated on acidification. Immunohistochemistry established their chloride cell localization, with NHE3 at the apical surface and the others localized to the basolateral membrane. These results suggest a mechanism by which Osorezan dace adapts to its acidic environment. Most likely, NHE3 on the apical side excretes H(+) in exchange for Na(+), whereas the electrogenic type 1 Na(+)-HCO(3)(-) cotransporter in the basolateral membrane provides HCO(3)(-) for neutralization of plasma using the driving force generated by Na(+)-K(+)-ATPase and carbonic anhydrase II. Increased expression of glutamate dehydrogenase was also observed in various tissues of acid-adapted dace, suggesting a significant role of ammonia and bicarbonate generated by glutamine catabolism.
authors.affiliation: Department of Biological Sciences, Tokyo Institute of Technology, Yokohama 226-8501, Japan.
authors.forename: Taku
authors.initials: T
authors.lastname: Hirata
authors.forename: Toyoji
authors.initials: T
authors.lastname: Kaneko
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Ono
authors.forename: Takeru
authors.initials: T
authors.lastname: Nakazato
authors.forename: Norihisa
authors.initials: N
authors.lastname: Furukawa
authors.forename: Sanae
authors.initials: S
authors.lastname: Hasegawa
authors.forename: Shigeo
authors.initials: S
authors.lastname: Wakabayashi
authors.forename: Munekazu
authors.initials: M
authors.lastname: Shigekawa
authors.forename: Min-Hwang
authors.initials: MH
authors.lastname: Chang
authors.forename: Michael F
authors.initials: MF
authors.lastname: Romero
authors.forename: Shigehisa
authors.initials: S
authors.lastname: Hirose
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D051400:Aquaporin 3; D020346:Aquaporins / Q000378:metabolism; D024402:Carbonic Anhydrase II / Q000235:genetics; D003001:Cloning, Molecular; D004790:Enzyme Induction; D005399:Fishes / Q000502:physiology*; D005618:Fresh Water / Q000737:chemistry*; D005880:Gills / Q000201:enzymology; D006863:Hydrogen-Ion Concentration; D007564:Japan; D007668:Kidney / Q000201:enzymology; D009865:Oocytes; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D027982:Sodium-Bicarbonate Symporters / Q000235:genetics / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics; D015854:Up-Regulation; D014982:Xenopus laevis
chemical_list: D020346:Aquaporins; D012333:RNA, Messenger; D027982:Sodium-Bicarbonate Symporters; D017923:Sodium-Hydrogen Exchangers; D051400:Aquaporin 3; D012964:Sodium; D024402:Carbonic Anhydrase II; D000254:Sodium-Potassium-Exchanging ATPase