Postprandial acid-base balance and ion regulation in freshwater and seawater-acclimated European flounder, Platichthys flesus

Josi R. Taylor, Jonathan M. Whittamore, Rod W. Wilson, Martin Grosell

Research output: Contribution to journalArticlepeer-review

53 Scopus citations


The effects of feeding on both acid-base and ion exchange with the environment, and internal acid-base and ion balance, in freshwater and seawater-acclimated flounder were investigated. Following voluntary feeding on a meal of 2.5-5% body mass and subsequent gastric acid secretion, no systemic alkaline tide or respiratory compensation was observed in either group. Ammonia efflux rates more than doubled from 489 ± 35 and 555 ± 64 μmol kg-1 h-1 under control conditions to 1,228 ± 127 and 1,300 ± 154 μmol kg-1 h-1 post-feeding in freshwater and seawater-acclimated fish, respectively. Based on predictions of gastric acid secreted during digestion, we calculated net postprandial internal base gains (i.e., HCO 3 - secreted from gastric parietal cells into the blood) of 3.4 mmol kg-1 in seawater and 9.1 mmol kg-1 in freshwater-acclimated flounder. However, net fluxes of ammonia, titratable alkalinity, Na+ and Cl- indicated that branchial Cl-/HCO 3 - and Na +/H+ exchange played minimal roles in counteracting these predicted base gains and cannot explain the absence of alkaline tide. Instead, intestinal Cl-/HCO 3 - exchange appears to be enhanced after feeding in both freshwater and seawater flounder. This implicates the intestine rather than the gills as a potential route of postprandial base excretion in fish, to compensate for gastric acid secretion.

Original languageEnglish (US)
Pages (from-to)597-608
Number of pages12
JournalJournal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology
Issue number6
StatePublished - Aug 2007
Externally publishedYes


  • Alkaline tide
  • Anion exchange
  • Bicarbonate secretion
  • Feeding
  • Osmoregulation

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Biochemistry
  • Physiology
  • Animal Science and Zoology
  • Endocrinology


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