Ruminant nutrition relies upon the symbiotic relationship that exists with microbial populations in the rumen. Urea transported across the ruminal epithelia and secreted by the salivary glands is a key source of nitrogen for microbial growth in the rumen. As ruminal urea transport can be mediated by specific UT-B urea transporters, this study investigated whether UT-B urea transporters were also present in the bovine salivary gland. Western blotting experiments detected only small amounts of UT-B protein in whole-cell lysate from the bovine parotid gland. In contrast, strong 32 to 34 and 40 kDa UT-B proteins were detected in parotid plasma membrane-enriched protein, showing the importance of using enriched samples. These signals were also detected in rumen and correspond to bovine UT-B1 and UT-B2 urea transporters, respectively. Further immunolocalization studies identified that these proteins were located in the ductal system of the parotid gland. This study, therefore, confirmed the presence of UT-B urea transporter protein in the bovine parotid salivary gland.
Copyright © 2013 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.