M. G. Mooij,1 B. A. De Koning,1 J. N. Samsom,2 D. J. Lindenbergh-Kortleve,2 D. Tibboel,1 S. N. De Wildt1; 1Erasmus MC - Sophia Children's Hospital, Rotterdam, Netherlands, 2Erasmus MC, Rotterdam, Netherlands

BACKGROUND: Intestinal drug transporters are involved in the uptake of numerous drugs. Data are scarce on their expression and activity in children. We aimed to visualize localization of selected transporters in neonatal and young infant intestinal tissue.
METHODS: Left-over paraffin tissue was obtained from neonates and young infants at small intestinal surgery. When microscopic inspection showed undamaged histology, MDR1, MRP2, OATP2B1 and PEPT1 protein were visualized using immunohistochemistry.
RESULTS: Samples from 12 infants were studied [median postnatal age 2.4 weeks (range 0-16.6) and gestational age at birth 33.3 weeks (25.3 - 40)]. We visualized MDR1 at the apical and lateral surface of the enterocyte (Figure 1), MRP2 and PEPT1 at the apical surface and OATP2B1 is seen intra-epithelial at the basolateral membrane.
CONCLUSION: We were able to specifically stain transporters in human neonatal and young infant small intestine. The localization is in line with adult localization (except OATP2B1 for which adult data our lacking) and our recent mRNA data showing MDR1, MRP2, OATP2B1 expression early in life. Protein expression data are needed to elucidate the ontogeny in activity of the drug transporters during development from fetal to child up to adult age.