The influence of luminal pH on transport of neutral and charged dipeptides by rat small intestine, in vitro

Norma Lister, Patrick D. Bailey, Ian D. Collier, C. A. Richard Boyd, J. Ramsey Bronk

Research output: Contribution to journalArticle

Abstract

Four hydrolysis-resistant dipeptides (D-phenylalanyl-L-alanine, D-phenylalanyl-L-glutamine, D-phenylalanyl-L-glutamate and D-phenylalanyl-L-lysine) were synthesized to investigate the effects of net charge on transmural dipeptide transport by isolated jejunal loops of rat small intestine. At a luminal pH of 7.4 and a concentration of 1 mM the two dipeptides with a net charge of - 1 and + 1 were transported at substantially slower rates (18 ± 1.3 and 8.4 ± 1.3 nmol min-1 (g dry wt.)-1, respectively) than neutral D-phenylalanyl-L-alanine and D-phenylalanyl-L-glutamine (87 ± 0.2 and 197 ± 14 nmol min-1 (g dry wt.)-1, respectively). We investigated the effects of luminal pH on dipeptide transport by varying the NaHCO3 content of Krebs Ringer perfusate equilibrated with 95%O2/5% CO2. The pH changes did not affect water transport, but serosal glucose appearance increased significantly at pH 6.8. Transmural transport of D-phenylalanyl-L-alanine and D-phenylalanyl-L-glutamine at pH 6.8 was stimulated (P < 0.01) by 61% and 49%, respectively, whereas the lower pH increased the rate for negatively charged D-phenylalanyl-L-glutamate by 306% (P < 0.01) and decreased that for positively charged D-phenylalanyl-L-lysine by 46% (P < 0.05). Increasing luminal pH to 8.0 inhibited D-phenylalanyl-L-alanine transport by 60%, whereas D-phenylalanyl-L-lysine transport was 60% faster.

Original languageEnglish
Pages (from-to)245-250
Number of pages6
JournalBiochimica et Biophysica Acta - Biomembranes
Volume1324
Issue number2
DOIs
Publication statusPublished - 13 Mar 1997

Keywords

  • Dipeptide
  • Intestine
  • pH
  • Rat
  • Transport

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