Intestinal base excretion in the seawater-adapted rainbow trout: A role in acid-base balance?

Rod W. Wilson, Kathleen M. Gilmour, Ray P. Henry, Chris M. Wood

Research output: Contribution to journalArticle

123 Scopus citations

Abstract

A potential role for the intestine of seawater-adapted teleosts in acid- base regulation was investigated following earlier reports of highly alkaline rectal fluids in the gulf toadfish Opsanus beta. Rectal samples taken from starved seawater-adapted rainbow trout had a high fluid pH (8.90 ± 0.03; mean ± S.E.M., N=13) and base (HCO3- + 2CO32-) content of 157±26 mequiv kg-1 (N=11). In trout fitted with rectal catheters, rectal fluid was voided at a rate of 0.47±0.11 ml kg-1 h-1 (N=8), giving a net base excretion rate of 114±15 μequiv kg-1 h-1 (N=7). Drinking rates averaged 3.12±0.48 ml kg-1 h-1 (N=8), and accounted for only 6% of the base excreted via the intestine, indicating substantial net transport of endogenously derived base into the intestine. Rectally excreted base was approximately balanced by an equivalent efflux of net acid from non-rectal sources (possibly as NH4+ excretion via the gills). Samples taken from four sites along the intestine revealed that the most anterior region (the pyloric intestine) was responsible for the majority of HCO3-+2CO32- accumulation. The pyloric intestine was subsequently perfused in situ to investigate possible mechanisms of base secretion. Net base fluxes were found to be dependent on luminal Cl-, 76% stimulated by amiloride, 20% inhibited by 10-4 mol l-1 acetazolamide, but unaffected by either 10-4 mol l-1 SITS or 2x10-5 mol l-1 DIDS. This suggests that the mechanism of base secretion within the pyloric intestine may involve a Cl-/HCO3--ATPase. It is speculated that intestinal base secretion may play a role in facilitating osmoregulation of seawater-adapted teleosts.

Original languageEnglish (US)
Pages (from-to)2331-2343
Number of pages13
JournalJournal of Experimental Biology
Volume199
Issue number10
StatePublished - Oct 1 1996

Keywords

  • acid-base balance
  • base secretion
  • bicarbonate
  • carbonate
  • drinking
  • intestine
  • marine teleost
  • Oncorhynchus mykiss
  • rainbow trout
  • rectal fluid

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Agricultural and Biological Sciences (miscellaneous)

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    Wilson, R. W., Gilmour, K. M., Henry, R. P., & Wood, C. M. (1996). Intestinal base excretion in the seawater-adapted rainbow trout: A role in acid-base balance? Journal of Experimental Biology, 199(10), 2331-2343.