Osmoregulation and salinity effects on the expression and activity of Na+,K(+)-ATPase in the gills of European sea bass, Dicentrarchus labrax (L.)

J Exp Zool. 1998 Oct 15;282(3):290-300. doi: 10.1002/(sici)1097-010x(19981015)282:3<290::aid-jez2>3.0.co;2-h.


The European sea bass, Dicentrarchus labrax, tolerates salinities ranging from freshwater (FW) to hypersaline conditions. In two experiments, we analysed changes in plasma ions, muscle water content (MWC), gill Na+,K(+)-ATPase activity, and alpha-subunit mRNA expression during the course of acclimation from 15 ppt salt water to FW or high salinity seawater (HSSW). In Experiment 1, fish (6.2 +/- 1.1 g) were acclimated from 15 ppt to either FW, 5, 15, 25, 50, or 60 ppt SW and sampled after 10 days. Gill Na+,K(+)-ATPase activity was stimulated in FW- and in 50 and 60 ppt SW-groups relative to the 15 ppt control group. In Experiment 2, subgroups of fish (89 +/- 7 g) were transferred from 15 ppt SW to FW or 50 ppt SW, and sampled 1, 2, 4, and 10 days later. Plasma osmolality, [Na+] and [Cl-] decreased in the FW-group and increased in the HSSW-group one day after transfer and lasting until day 10. This was accompanied by a pronounced increase in MWC in the FW-group and an insignificant decrease in the HSSW-group. The plasma [Na+]:[Cl-]-ratio increased markedly in the FW-group and decreased slightly in the HSSW-group, suggesting acid-base balance disturbances after transfer. Gill Na+,K(+)-ATPase activity was unchanged in 15 ppt SW but doubled in FW- and HSSW-groups after transfer. In both groups, this was preceded by a 2- to 5-fold elevation of the gill alpha-subunit Na+,K(+)-ATPase mRNA level. Thus increased expression of alpha-subunit mRNA is part of the molecular mechanism of both FW and SW acclimation in sea bass. Gill Na+,K(+)-ATPase Na(+)-, K(+)-, and ouabain-affinity were similar in fish acclimated to FW, 15 ppt, and HSSW, suggesting that identical isoforms of the catalytic subunit of the enzyme are expressed irrespective of salinity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptation, Physiological
  • Animals
  • Bass / metabolism*
  • Blotting, Northern
  • Chlorides / blood
  • Gills / enzymology*
  • Osmolar Concentration
  • Saline Solution, Hypertonic
  • Sodium / blood
  • Sodium Chloride
  • Sodium-Potassium-Exchanging ATPase / genetics
  • Sodium-Potassium-Exchanging ATPase / metabolism*
  • Water-Electrolyte Balance*
  • Xenopus laevis


  • Chlorides
  • Saline Solution, Hypertonic
  • Sodium Chloride
  • Sodium
  • Sodium-Potassium-Exchanging ATPase