Intestinal carbonic anhydrase, bicarbonate, and proton carriers play a role in the acclimation of rainbow trout to seawater

Martin Grosell, Katie M. Gilmour, Steven F. Perry

Research output: Contribution to journalArticlepeer-review

63 Scopus citations


Abrupt transfer of rainbow trout from freshwater to 65% seawater caused transient disturbances in extracellular fluid ionic composition, but homeostasis was reestablished 48 h posttransfer. Intestinal fluid chemistry revealed early onset of drinking and slightly delayed intestinal water absorption that coincided with initiation of NaCl absorption and HCO3- secretion. Suggestive of involvement in osmoregulation, relative mRNA levels for vacuolar H+-ATPase (V-ATPase), Na+-K+-ATPase, Na+/H+ exchanger 3 (NHE3), Na+-HCO 3- cotransporter 1, and two carbonic anhydrase (CA) isoforms [a general cytosolic isoform trout cytoplasmic CA (tCAc) and an extracellular isoform trout membrane-bound CA type IV (tCAIV)], were increased transiently in the intestine following exposure to 65% seawater. Both tCAc and tCAIV proteins were localized to apical regions of the intestinal epithelium and exhibited elevated enzymatic activity after acclimation to 65% seawater. The V-ATPase was localized to both basolateral and apical regions and exhibited a 10-fold increase in enzymatic activity in fish acclimated to 65% seawater, suggesting a role in marine osmoregulation. The intestinal epithelium of rainbow trout acclimated to 65% seawater appears to be capable of both basolateral and apical H+ extrusion, likely depending on osmoregulatory status and intestinal fluid chemistry.

Original languageEnglish (US)
Pages (from-to)R2099-R2111
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Issue number5
StatePublished - Nov 2007


  • HCO secretion
  • Intestinal H transport
  • tCAc
  • tCAIV
  • Water absorption

ASJC Scopus subject areas

  • Physiology


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