Peptide absorption after massive proximal small bowel resection: mechanisms of ileal adaptation.

<bold>Background: </bold>Protein absorption occurs as di- and tri-peptides via H(+)/peptide co-transporter-1 (PepT1).<bold>Aim: </bold>The aim of this study is to identify mechanisms of ileal adaptation after massive proximal enterectomy.<bold>Hypothesis: </bold>Ileal adaptation in uptake of peptides is mediated through upregulation of PepT1 gene expression.<bold>Study Design: </bold>Rats underwent 70% jejunoileal resection. Total mucosal cellular levels of messenger RNA (mRNA) and protein and transporter-mediated uptake per centimeter of the di-peptide glycyl-sarcosine (Gly-Sar) were compared in remnant ileum 1 and 4 weeks postoperatively to control and to 1-week sham laparotomy rats. Histomorphology, food consumption, and weights of rats were monitored.<bold>Results: </bold>After 70% resection, although mRNA per cell for PepT1 decreased at 1 week (p = 0.002), expression of mRNA at 4 weeks and protein at 1 and 4 weeks in remnant ileum were unchanged (p > 0.1). Ileal Gly-Sar uptake (V (max)-nanomoles per centimeter per minute, i.e., number of transporters per centimeter) increased at 1 and 4 weeks compared to control and 1-week sham (p < 0.05 each); K (m) (i.e., transporter function) was unchanged. Villous heights (millimeters) in remnant ileum increased at 1- and 4-week time points over controls (0.45 and 0.57 vs 0.21, resp; p < 0.001).<bold>Conclusions: </bold>Ileal adaptation to proximal resection for peptide absorption occurs through cellular proliferation (hyperplasia) and not through cellular upregulation of PepT1 mRNA or protein per enterocyte. [ABSTRACT FROM AUTHOR]