Urea and water permeability in dogfish (Squalus acanthias) gills

Peter Pärt, Patricia A. Wright, Chris M. Wood

Research output: Contribution to journalArticle

77 Scopus citations

Abstract

We used a perfused gill preparation from dogfish to investigate the origin of low branchial permeability to urea. Urea permeability (14C-urea) was measured simultaneously with diffusional water permeability (3H2O). Permeability coefficients for urea and ammonia in the perfused preparation were almost identical to in vivo values. The permeability coefficient of urea was 0.032 x 10-6 cm/sec and of 3H2O 6.55 x 10-6 cm/sec. Adrenalin (1 X 10-6 M) increased water and ammonia effluxes by a factor of 1.5 and urea efflux by a factor of 3.1. Urea efflux was almost independent of the urea concentration in the perfusion medium. The urea analogue thiourea in the perfusate had no effect on urea efflux, whereas the non-competitive inhibitor of urea transport, phloretin, increased efflux markedly. The basolateral membrane is approximately 14 times more permeable to urea than the apical membrane. We conclude that the dogfish apical membrane is extremely tight to urea, but the low apparent branchial permeability may also relate to the presence of an active urea transporter on the basolateral membrane that returns urea to the blood and hence reduces the apical urea gradient.

Original languageEnglish (US)
Pages (from-to)117-123
Number of pages7
JournalComparative Biochemistry and Physiology - A Molecular and Integrative Physiology
Volume119
Issue number1
DOIs
StatePublished - Jan 1998

Keywords

  • HO
  • Adrenalin
  • Gill
  • Gill perfusion
  • Permeability
  • Phloretin
  • Squalus acanthias
  • Thiourea
  • Urea

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Physiology

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