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This Article Full Text Full Text (PDF) All Versions of this Article: jas.2008-1710v1 87/10/3288    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Simmons, N. L. Articles by Stewart, G. S. PubMed PubMed Citation Articles by Simmons, N. L. Articles by Stewart, G. S.

Dietary regulation of ruminal bovine UT-B urea transporter expression and localization^1,2

N. L. Simmons^*, A. S. Chaudhry, C. Graham^*, E. S. Scriven, A. Thistlethwaite, C. P. Smith and G. S. Stewart^,3

^* School of Cellular and Molecular Biosciences, Division of Physiological Sciences, and and School of Agriculture, Food and Rural Development, Newcastle University, Newcastle-upon-Tyne, NE2 4HH, UK; and Faculty of Life Sciences, Smith Building, The University of Manchester, Manchester, M13 9NT, UK; and School of Biology and Environmental Science, University College Dublin, Dublin, Ireland

³ Corresponding author: gavin.stewart{at}ucd.ie

Facilitative UT-B urea transporters have been located in the gastrointestinal tract of numerous mammalian species. We have previously identified UT-B urea transporters within the epithelial layers of the bovine (b) rumen. The aim of this study was to test the hypothesis that ruminal bUT-B urea transporters are regulated by dietary intake. Six Limousine-cross steers (initial BW = 690 ± 51 kg) were separated into 2 groups fed a basic silage-based diet (RS) or a concentrate-based diet (RC) for 37 d and compared for ruminal morphology, content, and bUT-B expression. Analysis by reverse transcription-PCR showed that ruminal bUT-B2 mRNA expression was greater in RC-fed than RS-fed animals. Utilizing an anti-bUT-B antibody, we also detected a significant increase in bUT-B2 protein expression in RC-fed rumen (P < 0.05, n = 3). In agreement with these findings, immunolocalization studies of RC-fed ruminal tissue showed strong bUT-B signals throughout all epithelial layers, in contrast to weaker staining in RS-fed rumen that was more localized to the stratum basale. This study therefore confirmed that ruminal bUT-B urea transporter expression and localization were indeed altered by changes in dietary intake. We conclude that UT-B transporters play a significant role in the dietary regulation of bovine nitrogen balance.

Key Words: bovine UT-B2 urea transporter • dietary regulation • protein expression • rumen • UT-B urea transporter