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

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Abstract
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)

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