Growth factors regulation of rabbit sodium-dependent neutral amino acid transporter ATB(0) and oligopeptide transporter 1 mRNAs expression after enterectomy

Background: Sucessful intestinal adaptation after massive enterectomy is de pendent on increased efficiency of nutrient transport. However, midgut rese ction (MGR) in rabbits induces an initial decrease in sodium-dependent brus h border neutral amino acid transport, whereas parenteral epidermal growth factor (EGF) and growth hormone (GH) reverse this downregulation. We invest igated intestinal amino acid transporter B-0 (ATB(0)) and oligopeptide tran sporter 1 (PEPT 1) mRNA expression after resection and in response to EGF a nd/or GH. Methods: Rabbits underwent anesthesia alone (control) or proximal , midgut, and distal resections. Full-thickness intestine was harvested fro m all groups on postoperative day (POD) 7, and on POD 14 from control and M GR rabbits. A second group of MGR rabbits received EGF and/or GH for 7 days , beginning 7 days after resection. ATB(0) and PEPT I mRNA levels were dete rmined by Northern blot analysis. Results: In control animals, ileal ATB(0) mRNA abundance was three times higher than jejunal mRNA, whereas PEPT I mR NA expression was similar. By 7 and 14 days after MGR, jejunal ATB(0) mRNA abundance was decreased by 50% vs control jejunum. A 50% decrease in jejuna l PEPT 1 message was delayed until 14 days after MGR. Treatment with EGF pl us GH did not alter ATB(0) mRNA expression but doubled PEPT 1 mRNA in the j ejunum. Conclusion: The site of resection, time postresection, and growth f actors treatment differentially influence ATB(0) and PEPT 1 mRNA expression . Enhanced sodium dependent brush border neutral amino acid transport with GH plus EGF administration is independent of increased ATB(0) mRNA expressi on in rabbit small intestine after enterectomy.