Intestinal anion exchange in teleost water balance

Martin Grosell, Josi R. Taylor

Research output: Contribution to journalArticlepeer-review

60 Scopus citations


Simultaneous measurements of all major electrolytes including HCO3- and H+ as well as water demonstrated that fluids absorbed by the anterior intestine of the marine gulf toadfish under in vivo-like conditions on an overall net basis are hypertonic at 380 mOsm and acidic ([H+] = 27 mM). This unusual composition of fluids absorbed across the intestinal epithelium is due to the unusual intestinal fluid chemistry resulting from seawater ingestion and selective ion and water absorption along the gastro-intestinal tract. Measurement under near symmetrical conditions with high NaCl concentrations and low MgSO4 concentrations revealed absorption of iso-osmotic and much less acidic fluids by the intestinal epithelium, a situation resembling that of other water absorbing leaky vertebrate epithelia. Reduced luminal NaCl concentrations seen in vivo results in lower absolute water absorption rates but higher Cl-/HCO3- exchange rates which are associated with higher net H+ absorption rates. It appears that apical anion exchange is important for net Cl- uptake by the marine teleost intestine especially when luminal NaCl concentrations are low and/or when MgSO4 concentrations are high. Observations indicate that fluid absorption from solutions of low NaCl but high MgSO4 concentrations is energetically more demanding than absorption from NaCl rich solutions at the level of the intestinal epithelium. Furthermore, the high luminal MgSO4 concentration which is an unavoidable consequence of seawater ingestion projects a demand for renal and branchial compensation for intestinal MgSO4 uptake and absorption of hypertonic and acidic fluid by the intestine.

Original languageEnglish (US)
Pages (from-to)14-22
Number of pages9
JournalComparative Biochemistry and Physiology - A Molecular and Integrative Physiology
Issue number1 SPEC. ISS.
StatePublished - Sep 2007


  • Acid absorption
  • Hypertonic absorbate
  • Intestine
  • Marine fish
  • Water absorption

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Physiology


Dive into the research topics of 'Intestinal anion exchange in teleost water balance'. Together they form a unique fingerprint.

Cite this