title: Efflux properties of basolateral peptide transporter in human intestinal cell line Caco-2.
abstract: Small peptides and some pharmacologically active compounds are absorbed from the small intestine by the apical H(+)-coupled peptide transporter 1 (PEPT1) and the basolateral peptide transporter. Here we investigated the efflux properties of the basolateral peptide transporter in Caco-2 cells using two strategies, efflux measurements and a kinetic analysis of transepithelial transport of glycylsarcosine (Gly-Sar). [(14)C]Gly-Sar efflux through the basolateral membrane was not affected significantly by the external pH. Both approaches revealed that the basolateral peptide transporter was saturable in the efflux direction, and that the affinity was lower than that in the influx direction. For two peptide-like drugs, there was no difference in substrate recognition by the basolateral peptide transporter between the two sides of the membrane. Using the kinetic parameters of PEPT1 and the basolateral peptide transporter, a computational model of Gly-Sar transport in Caco-2 cells was constructed. The simulation fitted the experimental data well. Our findings suggested that substrate affinity of the basolateral peptide transporter is apparently asymmetric, but pH-dependence and substrate specificity are symmetric for the two directions of transport. The behaviour of Gly-Sar in Caco-2 cells could be predicted by a mathematical model describing the peptide transporters.
authors.affiliation: Department of Pharmacy, Kyoto University Hospital, Faculty of Medicine, Kyoto University, Sakyo-ku, 606-8507 Kyoto, Japan. inui@kuhp.kyoto-u.ac.jp
authors.forename: Megumi
authors.initials: M
authors.lastname: Irie
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Terada
authors.forename: Masahiro
authors.initials: M
authors.lastname: Okuda
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Inui
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D018938:Caco-2 Cells; D002250:Carbon Radioisotopes; D000077722:Ceftibuten; D016764:Cell Polarity / Q000502:physiology*; D002511:Cephalosporins / Q000494:pharmacology; D003198:Computer Simulation; D003493:Cyclacillin / Q000494:pharmacology; D004151:Dipeptides / Q000493:pharmacokinetics; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007413:Intestinal Mucosa / Q000166:cytology* / Q000378:metabolism*; D007700:Kinetics; D016014:Linear Models; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008954:Models, Biological
chemical_list: D000900:Anti-Bacterial Agents; D002250:Carbon Radioisotopes; D002511:Cephalosporins; D004151:Dipeptides; D026901:Membrane Transport Proteins; C004194:glycylsarcosine; D003493:Cyclacillin; C043912:peptide permease; D000077722:Ceftibuten