Proceedings of The Physiological Society
University College Dublin (2009) Proc Physiol Soc 15, PC186
Differential expression of UT-B urea transporters in the human gastrointestinal tract
1. School of Biology and Environmental Science, University College Dublin, Dublin, Ireland.
Facilitative UT-B urea transporters enable the passage of urea across cell membranes (1). Gastrointestinal urea transporters are thought to play a significant role in the symbiotic urea nitrogen salvaging process that occurs between mammalian hosts and their gut bacteria (2). This study investigated the expression of UT-B urea transporters along the human gastrointestinal tract, particularly in the colon. Immunoblot analysis showed that UT-B proteins (purchased from AMS Biotechnology) were present throughout the human gastrointestinal tract and most strongly expressed in the caecum and colon. Within the colon, a 35 kDa signal was deglycosylated to a 30 kDa protein after one hour pre-incubation with PNGaseF enzyme. Glycosylated UT-B protein expression was greater in the proximal colon than in the distal colon. This differential pattern of colonic expression was also observed for several other proteins involved in nutrient transport mechanisms - such as NHE3 and NaKATPase. Finally, at the cellular level UT-B transporters were located in the basolateral region of colonocytes situated in the upper portion of the colonic crypts. These results illustrate a differential expression of glycosylated UT-B transporters along the human gastrointestinal tract, correlating to regions that contain the largest populations of intestinal bacteria. These data therefore suggest an important role for urea transporters in maintaining the symbiotic relationship between humans and their gut bacteria.
Where applicable, experiments conform with Society ethical requirements