Growth hormone and epidermal growth factor together enhance amino acid transport systems B 0,+ and A in remnant small intestine after massive enterectomy

Abstract

Background Sodium-dependent brush border nutrient transport is decreased 2 weeks after massive enterectomy. This downregulation is ameliorated by a 1-week infusion of parenteral growth hormone (GH) and epidermal growth factor (EGF) started 1 week after resection. We hypothesized that glutamine (GLN) transport would be enhanced by earlier and longer growth factor infusion, with differential effects on the Na +-dependent GLN transport systems A, B 0,+, and B 0/ASCT2. Materials and methods New Zealand White rabbits underwent 70% small bowel resection then immediately received parenteral EGF, GH, both, or neither for 2 weeks. Na +-dependent 3H-GLN uptake by jejunal and ileal brush-border membrane vesicles was measured and the contribution of systems A, B 0,+, and B 0 then determined by competitive inhibition. Data were analyzed using one-way analysis of variance. Results In nonresected animals, the relative contribution of the systems was similar in jejunum (A, 9%, B 0,+, 20%; and B 0, 71%) and ileum (A, 13%; B 0,+, 27%; and B 0, 60%). Na +-dependent GLN uptake was reduced by half in resected, untreated controls, primarily because of decreased B 0 activity. EGF or GH alone did not affect Na +-dependent GLN transport, but as a combination, increased uptake in the residual ileum and jejunum by 144% and 150%, respectively, over resected controls ( P < 0.05). This was twice that achieved by delayed and shorter-duration combination treatment. This augmentation was due to a 6.1- to 8.2-fold increase in system A as well as a 3.8- to 3.9-fold enhancement of system B 0,+ activity in remnant ileum and jejunum ( P < 0.01). Conclusions Parenteral EGF and GH, given in combination for 2 weeks immediately after massive enterectomy, synergistically enhance GLN uptake by systems A and B 0,+.