The Journal of Membrane Biology

, Volume 239, Issue 3, pp 123–130 | Cite as

UT-B1 Mediates Transepithelial Urea Flux in the Rat Gastrointestinal Tract

  • Danielle Collins
  • Caragh Walpole
  • Elizabeth Ryan
  • Desmond Winter
  • Alan Baird
  • Gavin StewartEmail author


The process of urea nitrogen salvaging plays a vital role in the symbiotic relationship between mammals and their intestinal bacteria. The first step in this process requires the movement of urea from the mammalian bloodstream into the gastrointestinal tract lumen via specialized proteins known as facilitative urea transporters. In this study, we examined both transepithelial urea fluxes and urea transporter protein abundance along the length of the rat gastrointestinal tract. Urea flux experiments that used rat gastrointestinal tissues showed significantly higher transepithelial urea transport was present in caecum and proximal colon (P < 0.01, n = 8, analysis of variance [ANOVA]). This large urea flux was significantly inhibited by 1,3,dimethylurea (P < 0.001, n = 8, ANOVA) and thiourea (P < 0.05, n = 6, unpaired t-test), both known blockers of facilitative urea transporters. Immunoblotting analysis failed to detect any UT-A protein within rat gastrointestinal tissue protein samples. In contrast, a 30-kDa UT-B1 protein was strongly detected in both caecum and proximal colon samples at significantly higher levels compared to the rest of the gastrointestinal tract (P < 0.01, n = 4, ANOVA). We therefore concluded that UT-B1 mediates the transepithelial movement of urea that occurs in specific distal regions of the rat gastrointestinal tract.


UT-A UT-B Transepithelial urea transport Dimethylurea Intestine Colon 



This work was funded by the Irish Research Council for Science, Engineering and Technology (IRCSET) postgraduate scholarship scheme.


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Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  • Danielle Collins
    • 1
    • 2
  • Caragh Walpole
    • 3
  • Elizabeth Ryan
    • 1
    • 2
  • Desmond Winter
    • 1
  • Alan Baird
    • 2
  • Gavin Stewart
    • 3
    Email author
  1. 1.Institute for Clinical Outcomes Research and EducationSt. Vincent’s University HospitalDublinIreland
  2. 2.College of Life SciencesConway Institute of Biomedical and Biomolecular ScienceDublinIreland
  3. 3.School of Biology and Environmental ScienceUniversity College Dublin BelfieldDublinIreland

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