TY - JOUR T1 - Species-Dependent Uptake of Glycylsarcosine but Not Oseltamivir in <em>Pichia pastoris</em> Expressing the Rat, Mouse, and Human Intestinal Peptide Transporter PEPT1 JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 1328 LP - 1335 DO - 10.1124/dmd.111.044263 VL - 40 IS - 7 AU - Yongjun Hu AU - Xiaomei Chen AU - David E. Smith Y1 - 2012/07/01 UR - http://dmd.aspetjournals.org/content/40/7/1328.abstract N2 - The purpose of this study was to determine whether glycylsarcosine (a model dipeptide) and oseltamivir (an antiviral prodrug) exhibited a species-dependent uptake in yeast Pichia pastoris expressing the rat, mouse, and human homologs of PEPT1. Experiments were performed with [3H]glycylsarcosine (GlySar) in yeast P. pastoris expressing human, mouse, and rat peptide transporter 1 (PEPT1), in which uptake was examined as a function of time, concentration, potential inhibitors, and the dose-response inhibition of GlySar by oseltamivir. Studies with [14C]oseltamivir were also performed under identical experimental conditions. We found that GlySar exhibited saturable uptake in all three species, with Km values for human (0.86 mM) &gt; mouse (0.30 mM) &gt; rat (0.16 mM). GlySar uptake in the yeast transformants was specific for peptides (glycylproline) and peptide-like drugs (cefadroxil, cephradine, and valacyclovir), but was unaffected by glycine, l-histidine, cefazolin, cephalothin, cephapirin, acyclovir, 4-acetamido-4′-isothiocyanostilbene-2,2′-disulfonic acid, tetraethylammonium, and elacridar. Although oseltamivir caused a dose-dependent inhibition of GlySar uptake [IC50 values for human (27.4 mM) &gt; rat (18.3 mM) &gt; mouse (10.7 mM)], the clinical relevance of this interaction would be very low in humans. Of importance, oseltamivir was not a substrate for the intestinal PEPT1 transporter in yeast expressing the three mammalian species tested. Instead, the prodrug exhibited nonspecific binding to the yeast vector and PEPT1 transformants. Finally, the mouse appeared to be a better animal model than the rat for exploring the intestinal absorption and pharmacokinetics of peptides and peptide-like drugs in human. ER -