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.
|Number of pages
|Journal of Experimental Zoology Part A: Ecological Genetics and Physiology
|Published - 1 Aug 2011
Scopus Subject Areas
- Ecology, Evolution, Behavior and Systematics
- Animal Science and Zoology
- Molecular Biology