Intestinal HCO3- secretion in marine teleost fish: Evidence for an apical rather than a basolateral Cl-/HCO3- exchanger

Martin Grosell, C. N. Laliberte, S. Wood, F. B. Jensen, C. M. Wood

Research output: Contribution to journalArticle

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Abstract

Intestinal fluid was collected from 11 marine teleost fish from the Baltic sea and the Pacific ocean. The anterior, mid and posterior segments of the intestine contained 33-110 mM of HCO3- equivalents (with exception of the Atlantic cod which contained only 5-15 mM). Considering literature values of transepithelial potentials and concentration gradients, these high levels of HCO3- equivalents are probably the result of active HCO3- transport. Possible HCO3- transport mechanisms were studied in the Pacific sanddab (Citharichthys sordidus) in vitro. Measurements of net secretion of HCO3- equivalents across the intestinal epithelium revealed mucosal DIDS sensitivity (10-4 M) and Cl--dependence of the HCO3- equivalent net flux, but no serosal DIDS (10-4 M) sensitivity. Net Na+ uptake was abolished in the absence of Cl-, but some Cl- uptake persisted in the absence of Na+, at a rate similar to that of net HCO3- secretion. Anterior, mid and posterior segments of the intestine performed similarly. These observations support the presence of an apical rather than a basolateral Cl-/HCO3- exchanger and thus contrast the currently accepted model for intestinal HCO3- secretion. This apical Cl-/HCO3- exchanger alone, however, is not sufficient for maintaining the observed HCO3- equivalents gradient in vivo. We suggest a coupling of cytosolic carbonic anhydrase, a basolateral proton pump and the apical Cl-/HCO3- exchanger to explain the intestinal HCO3- transport.

Original languageEnglish
Pages (from-to)81-95
Number of pages15
JournalFish Physiology and Biochemistry
Volume24
Issue number2
DOIs
StatePublished - Nov 13 2001
Externally publishedYes

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Keywords

  • Active transport
  • Cl dependence
  • Cl/HCO exchange
  • DIDS
  • HCO secretion
  • Intestinal fluid composition
  • Intestine
  • Ion and water absorption
  • Marine teleost

ASJC Scopus subject areas

  • Aquatic Science
  • Biochemistry, Genetics and Molecular Biology(all)
  • Biochemistry
  • Physiology
  • Physiology (medical)

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