UT-B is expressed in bovine rumen: Potential role in ruminal urea transport

G. S. Stewart, C. Graham, S. Cattell, T. P L Smith, N. L. Simmons, C. P. Smith

    Research output: Contribution to journalArticlepeer-review


    The UT-A (SLC14a2) and UT-B (SLC14a1) genes encode a family of specialized urea transporter proteins that regulate urea movement across plasma membranes. In this report, we describe the structure of the bovine UT-B (bUT-B) gene and characterize UT-B expression in bovine rumen. Northern analysis using a full-length bUT-B probe detected a 3.7-kb UT-B signal in rumen. RT-PCR of bovine mRNA revealed the presence of two UT-B splice variants, bUT-B1 and bUT-B2, with bUT-B2 the predominant variant in rumen. Immunoblotting studies of bovine rumen tissue, using an antibody targeted to the NH2-terminus of mouse UT-B, confirmed the presence of 43- to 54-kDa UT-B proteins. Immunolocalization studies showed that UT-B was mainly located on cell plasma membranes in epithelial layers of the bovine rumen. Using chamber measurements of ruminal transepithelial transport of 14C-labeled urea indicated that urea flux was characteristically inhibited by phloretin. We conclude that bUT-B is expressed in the bovine rumen and may function to transport urea into the rumen as part of the ruminant urea nitrogen salvaging process.
    Original languageEnglish
    Pages (from-to)R605-R612
    JournalAJP: Regulatory, Integrative and Comparative Physiology
    Issue number2
    Publication statusPublished - Aug 2005


    • Facilitative transporter
    • Nitrogen balance
    • Phloretin
    • Thionicotinamide
    • Transepithelial flux


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