Distribution and abundance of nutrient transporter mRNA in the intestinal tract of the black bear, Ursus americanus

End products of digestion are absorbed by the body through the action of transporter proteins expressed on the apical membrane of intestinal epithelia] cells. We investigated the mRNA abundance and distribution of a peptide transporter (PepT I), a glucose transporter (SGLT 1), two amino acid transporters (NBAT and b(o,+)AT), and a digestive enzyme, aminopeptidase N (APN), in the intestinal tract of black bears (Ursus americanus). Intestinal total RNA was isolated from 10 bears and abundance of PepT 1, SGLT 1, NBAT, b(o,+)AT, and APN mRNA were determined by Northern blots. Abundance of PepT1 (P < 0.05), APN (P < 0.05), and SGLTI (P < 0.0001) changed quadratically from the proximal to distal intestine with abundance being greatest in the midregion. Abundance of b(o,+)AT mRNA increased linearly (P < 0.05) from the proximal to distal intestine. The number of molecules of mRNA/ng of total RNA for each gene was determined using Real-Time PCR. PepT I mRNA was present at 10-fold or greater levels than amino acid transporter mRNA in all segments of the intestine, suggesting that di- and tripeptides constitute a major form in which amino acids are absorbed in the black bear. The abundance of NBAT and b(o,+)AT mRNA was greater towards the distal intestine, suggesting a role in salvaging unabsorbed amino acids. (c) 2006 Elsevier Inc. All rights reserved.