Dietary regulation of ruminal bovine UT-B urea transporter expression and localization.
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.
Simmons
N L
NL
School of Cellular and Molecular Biosciences, Newcastle University, Newcastle-upon-Tyne, UK.
Chaudhry
A S
AS
Graham
C
C
Scriven
E S
ES
Thistlethwaite
A
A
Smith
C P
CP
Stewart
G S
GS
D000821:Animal Feed; D000818:Animals; D002417:Cattle; D004032:Diet; D005786:Gene Expression Regulation / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D015151:Immunoblotting / Q000662:veterinary; D008297:Male; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms / Q000378:metabolism; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D012417:Rumen / Q000378:metabolism* / Q000648:ultrastructure; D000096982:Urea Transporters
D026901:Membrane Transport Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D000096982:Urea Transporters