The role of a UT‐A urea transporter in human small intestine (897.2)

Abstract

Urea transporters (UTs) encoded by the Slc14a1 (UT‐B) and Slc14a2 (UT‐A) genes facilitate the movement of urea across plasma membranes. Urea flux into the gastrointestinal tract enhances the growth of bacterial populations by providing a source of nitrogen, thus maintaining the symbiotic relationship between humans and their intestinal bacteria (Stewart 2011). A previous study identified the UT‐B1 urea transporter within the human colon, localized to the basolateral membrane of colonocytes (Collins et al. 2010). The aim of this present study was to investigate for the expression of UT‐A urea transporters in the human gastrointestinal tract. Using primers for UT‐A1, RT‐PCR analysis detected the expected RNA‐derived 682bp signal primarily in the small intestine, compared to stomach and colon. Using different samples of small intestine cDNA (AMS Biotechnology), UT‐A1 expression was shown to be higher in the jejunum and ileum than the duodenum. Western blotting experiments were then performed using human ileum tissue samples. Using a characterised rat UT‐A1 antibody (L194) (Nielsen et al. 1996), a 120kDa glycosylated UT‐A1 protein could be detected in protein samples from ileostomy patients. In contrast, ileum samples from surgical resection tissue showed UT‐A1 signals of around 170kDa. This study shows that UT‐A1 urea transporters are expressed in the human ileum. Since high levels of bacteria exist in this region, this suggests a physiological function for UT‐A1 in the urea nitrogen salvaging mechanism that is crucial for human gastrointestinal health.Grant Funding Source: Supported by Science Foundation Ireland (SFI) and University College Dublin (UCD)