Abstract
The primary purpose of this study was to evaluate the intestinal permeability (P(eff)) of N-formyl-methionyl-leucyl-phenylalanine (fMet-Leu-Phe), a bacterially derived chemotactic tripeptide, in the duodenum, jejunum, ileum, and colon of wild-type and PepT1 knockout mice. A secondary purpose was to determine if the presence of intestinal PepT1 translated into fMet-Leu-Phe directed neutrophil migration in these animals. Using an in situ single pass perfusion technique, the P(eff) of [(3)H]fMet-Leu-Phe was substantially reduced in the duodenum, jejunum, and ileum of PepT1 knockout mice as compared to wild-type animals. In contrast, the P(eff) of [(3)H]fMet-Leu-Phe in colon was unchanged between genotypes and about 5% of that in small intestine. Jejunal uptake of [(3)H]fMet-Leu-Phe was specific for PepT1 and saturable with an intrinsic K(0.5) of 1.6 mM. The peptide/histidine transporters PhT1 and PhT2 were not involved in [(3)H]fMet-Leu-Phe uptake. Myeloperoxidase activity (a measure of neutrophil migration) was significantly increased following 4 h perfusions of 10 μM fMet-Leu-Phe in the jejunum of wild-type mice and was abolished by 50 mM glycylglycine; no change was observed in the jejunum of PepT1 knockout mice. Likewise, fMet-Leu-Phe perfusions had no effect on myeloperoxidase activity in the colon of either genotype. In conclusion, these findings demonstrated that PepT1 had a major influence on the permeability of fMet-Leu-Phe in duodenum, jejunum, and ileum in wild-type mice and on inflammatory response in intestinal regions that expressed PepT1.