title: UT-B is expressed in bovine rumen: potential role in ruminal urea transport.
abstract: 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. Ussing chamber measurements of ruminal transepithelial transport of (14)C-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.
authors.affiliation: Faculty of Life Sciences, Medical School, The University of Manchester, Manchester M13 9PT, UK.
authors.forename: G S
authors.initials: GS
authors.lastname: Stewart
authors.forename: C
authors.initials: C
authors.lastname: Graham
authors.forename: S
authors.initials: S
authors.lastname: Cattell
authors.forename: T P L
authors.initials: TP
authors.lastname: Smith
authors.forename: N L
authors.initials: NL
authors.lastname: Simmons
authors.forename: C P
authors.initials: CP
authors.lastname: Smith
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D015139:Blotting, Southern; D015153:Blotting, Western; D002417:Cattle / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D005260:Female; D007150:Immunohistochemistry; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012417:Rumen / Q000378:metabolism*; D014018:Tissue Distribution; D014981:Xenopus; D000096982:Urea Transporters
chemical_list: D026901:Membrane Transport Proteins; D000096982:Urea Transporters