Growth Factors Regulation of Rabbit Sodium-Dependent Neutral Amino Acid Transporter ATB0 and Oligopeptide Transporter 1 mRNAs Expression after Enterectomy

Background: Sucessful intestinal adaptation after massive enterectomy is dependent on increased efficiency of nutrient transport. However, midgut resection (MGR) in rabbits induces an initial decrease in sodium-dependent brush border neutral amino acid transport, whereas parenteral epidermal growth factor (EGF) and growth hormone (GH) reverse this downregulation. We investigated intestinal amino acid transporter B° (ATB°) and oligopeptide transporter 1 (PEPT 1) mRNA expression after resection and in response to EGF and/or GH. Methods: Rabbits underwent anesthesia alone (control) or proximal, midgut, and distal resections. Full-thickness intestine was harvested from all groups on postoperative day (POD) 7, and on POD 14 from control and MGR rabbits. A second group of MGR rabbits received EGF and/or GH for 7 days, beginning 7 days after resection. ATB° and PEPT 1 mRNA levels were determined by Northern blot analysis. Results: In control animals, ileal ATB° mRNA abundance was three times higher than jejunal mRNA, whereas PEPT 1 mRNA expression was similar. By 7 and 14 days after MGR, jejunal ATB° mRNA abundance was decreased by 50% us control jejunum. A 50% decrease in jejunal PEPT 1 message was delayed until 14 days after MGR. Treatment with EGF plus GH did not alter ATB° mRNA expression but doubled PEPT 1 mRNA in the jejunum. Conclusion: The site of resection, time postresection, and growth factors treatment differentially influence ATB° and PEPT 1 mRNA expression. Enhanced sodium-dependent brush border neutral amino acid transport with GH plus EGF administration is independent of increased ATB° mRNA expression in rabbit small intestine after enterectomy. (journal of Parenteral and Enteral Nutrition 25:65-72, 2001)