RT Journal Article SR Electronic T1 Human Intestinal PEPT1 Transporter Expression and Localization in Preterm and Term Infants JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 1014 OP 1019 DO 10.1124/dmd.115.068809 VO 44 IS 7 A1 Miriam G. Mooij A1 Barbara E. A. de Koning A1 Dicky J. Lindenbergh-Kortleve A1 Ytje Simons-Oosterhuis A1 Bianca D. van Groen A1 Dick Tibboel A1 Janneke N. Samsom A1 Saskia N. de Wildt YR 2016 UL http://dmd.aspetjournals.org/content/44/7/1014.abstract AB The intestinal influx oligopeptide transporter peptide transporter 1 (PEPT1) (SLC15A1) is best known for nutrient-derived di- and tripeptide transport. Its role in drug absorption is increasingly recognized. To better understand the disposition of PEPT1 substrate drugs in young infants, we studied intestinal PEPT1 mRNA expression and tissue localization across the pediatric age range. PEPT1 mRNA expression was determined using real-time reverse-transcription polymerase chain reaction in small intestinal tissues collected from surgical procedures (neonates and infants) or biopsies (older children and adolescents). PEPT1 mRNA relative to villin mRNA expression was compared between neonates/infants and older children/adolescents. PEPT1 was visualized in infant tissue using immunohistochemical staining. Other transporters [multidrug resistance protein 1 (MDR1), multidrug resistance–like protein 2 (MRP2), and organic anion transporter polypeptide 2B1 (OATP2B1)] were also stained to describe the localization in relation to PEPT1. Twenty-six intestinal samples (n = 20 neonates/infants, n = 2 pediatric, n = 4 adolescents) were analyzed. The young infant samples were collected at a median (range) gestational age at birth of 29.2 weeks (24.7–40) and postnatal age of 2.4 weeks (0–16.6). The PEPT1 mRNA expression of the neonates/infants was only marginally lower (0.8-fold) than the older children (P < 0.05). Similar and clear apical PEPT1 and MRP2 staining, apical and lateral MDR1 staining, and intraepithelial OATP2B1 staining at the basolateral membrane of the enterocyte were detected in 12 infant and 2 adolescent samples. Although small intestinal PEPT1 expression tended to be lower in neonates than in older children, this difference is small and tissue distribution is similar. This finding suggests similar oral absorption of PEPT1 substrates across the pediatric age range.