Modulation of ion transporter expression in gill mitochondrion-rich cells of eels acclimated to low-Na(+) or-Cl(-) freshwater

J Exp Zool A Ecol Genet Physiol. 2011 Aug 1;315(7):385-93. doi: 10.1002/jez.681. Epub 2011 Mar 31.


In this study, we aimed to establish an experimental model to study the role of the gill mitochondrion-rich cells (MRCs) of freshwater fish in Na(+) uptake and to examine the effect of adjusting external Na(+) and Cl(-) ions on selected ion transporters in gill MRCs. Japanese eels (Anguilla japonica) acclimated to deionized (DI) water for 2 weeks were transferred directly to (a) ion-supplemented artificial freshwater (AF), (b) Na(+) -deficient AF, or (c) Cl(-) -deficient AF for 2 days. The effects of the transfer on the expression levels of ion transporters in isolated gill cells were investigated. Our data demonstrated that the 2-day acclimation in ion-supplemented AF, Na(+) -deficient AF, or Cl(-) -deficient AF led to a significant increase in serum osmolarity attributed mainly to an increase in serum Na(+) and/or Cl(-) levels when compared with DI-acclimated eel. Significant inductions of V-type H(+) -ATPase (V-H(+) -ATPase) and cotransporter (NBC1) mRNA expression in gill MRCs were detected in AF-acclimated fish. In fish acclimated to Na(+) -deficient AF, mRNA expression levels of V-H(+) -ATPase, NBC1, and Na(+) /H(+) -exchanger-3 (NHE3) were significantly increased in MRCs. Fish acclimated to Cl(-) -deficient AF showed no observable change in expression levels of ion transporters in gill MRCs. In addition, expression levels of ion transporters in pavement cells were stable throughout the 2-day experiments. These data indicate that the level of Na(+) in freshwater is important for altering the mRNA expression of ion transporters in gill MRCs, which supports the notion that gill MRCs play important roles in freshwater Na(+) uptake.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acclimatization / physiology*
  • Animals
  • Chlorides / metabolism
  • Eels / metabolism*
  • Fresh Water
  • Gene Expression Regulation
  • Gills / cytology*
  • Gills / metabolism
  • Ions
  • Mitochondria / metabolism*
  • RNA, Messenger / metabolism
  • Sodium / deficiency
  • Sodium / metabolism
  • Sodium-Bicarbonate Symporters / genetics
  • Sodium-Bicarbonate Symporters / metabolism
  • Sodium-Hydrogen Exchangers / genetics
  • Sodium-Hydrogen Exchangers / metabolism
  • Symporters / genetics
  • Symporters / metabolism*
  • Vacuolar Proton-Translocating ATPases / genetics
  • Vacuolar Proton-Translocating ATPases / metabolism


  • Chlorides
  • Ions
  • RNA, Messenger
  • Sodium-Bicarbonate Symporters
  • Sodium-Hydrogen Exchangers
  • Symporters
  • Sodium
  • Vacuolar Proton-Translocating ATPases