title: Significance and regional dependency of peptide transporter (PEPT) 1 in the intestinal permeability of glycylsarcosine: in situ single-pass perfusion studies in wild-type and Pept1 knockout mice.
abstract: The purpose of this study was to evaluate the role, relevance, and regional dependence of peptide transporter (PEPT) 1 expression and function in mouse intestines using the model dipeptide glycylsarcosine (GlySar). After isolating specific intestinal segments, in situ single-pass perfusions were performed in wild-type and Pept1 knockout mice. The permeability of [(3)H]GlySar was measured as a function of perfusate pH, dipeptide concentration, potential inhibitors, and intestinal segment, along with PEPT1 mRNA and protein. We found the permeability of GlySar to be saturable (K(m) = 5.7 mM), pH-dependent (maximal value at pH 5.5), and specific for PEPT1; other peptide transporters, such as PHT1 and PHT2, were not involved, as judged by the lack of GlySar inhibition by excess concentrations of histidine. GlySar permeabilities were comparable in the duodenum and jejunum of wild-type mice but were much larger than that in ileum (approximately 2-fold). A PEPT1-mediated permeability was not observed for GlySar in the colon of wild-type mice (<10% residual uptake compared to proximal small intestine). Moreover, GlySar permeabilities were very low and not different in the duodenum, jejunum, ileum, and colon of Pept1 knockout mice. Functional activity of intestinal PEPT1 was confirmed by real-time polymerase chain reaction and immunoblot analyses. Our findings suggest that a loss of PEPT1 activity (e.g., due to polymorphisms, disease, or drug interactions) should have a major effect in reducing the intestinal absorption of di-/tripeptides, peptidomimetics, and peptide-like drugs.
authors.affiliation: University of Michigan, 4742 Medical Sciences II, 1150 W Medical Center Drive, Ann Arbor, MI 48109-5633, USA.
authors.forename: Dilara
authors.initials: D
authors.lastname: Jappar
authors.forename: Shu-Pei
authors.initials: SP
authors.lastname: Wu
authors.forename: Yongjun
authors.initials: Y
authors.lastname: Hu
authors.forename: David E
authors.initials: DE
authors.lastname: Smith
mesh_terms: D000818:Animals; D003106:Colon / Q000378:metabolism*; D004151:Dipeptides / Q000493:pharmacokinetics*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006863:Hydrogen-Ion Concentration; D015151:Immunoblotting; D007408:Intestinal Absorption; D007421:Intestine, Small / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D000074011:Peptide Transporter 1; D010477:Perfusion; D010539:Permeability; D020133:Reverse Transcriptase Polymerase Chain Reaction; D027981:Symporters / Q000235:genetics / Q000502:physiology*
chemical_list: D004151:Dipeptides; D000074011:Peptide Transporter 1; C489941:Slc15a1 protein, mouse; D027981:Symporters; C004194:glycylsarcosine