The oligopeptide transporter 2-mediated reabsorption of entecavir in rat kidney

We investigated whether entecavir is a substrate of the oligopeptide transporter 2 (PEPT2) and whether reabsorption of entecavir is mediated by PEPT2 as well as what is the contribution of PEPT2 to entecavir reabsorption during urinary excretion. Entecavir uptake in transfected cells and rat kidney slices, changes in urine entecavir concentrations following isolated kidney perfusion and in vivo entecavir plasma and urine concentrations were determined with LC-MS/MS. In hPEPT2-HELA cells, entecavir uptake was significantly higher compared to vector-HELA cells and was sharply inhibited by Gly-sar and JBP485, and there were two distinct transport systems. The Km and Vmax of entecavir were 427 (mu M) and 1.60 (nmol/mg protein/30s) (low-affinity, high-velocity system) and 24.0 (mu M) and 0.296 (nmol/mg protein/30s) (high-affinity, low-velocity system). In rat kidney slices, uptake of entecavir was not markedly inhibited by Gly-sar. In isolated kidney perfusion experiments, entecavir cumulative urinary excretion was statistically significant at 45 and 60 min. CLR(4 degrees C), CLR(37 degrees C Control) and CLR(37 degrees C Experiment) were 12.6, 27.6 and 36 (ml/min/kg), respectively. CLTS and TR rate (for PEPT2) were 25.3 and 9.4 (ml/min/kg). In vivo, the cumulative urinary excretion of entecavir had statistical significance at 3 and 4 h with CLR(Control) and CLR(Experiment) values of 31 and 42 (ml/min/kg), respectively. The CLTS and TR rate (for PEPT2) were 32 and 11.6 (ml/min/kg), respectively. The present study demonstrated that entecavir is a substrate of PEPT2. Moreover, reabsorption of entecavir is mediated by PEPT2, and 25% of urinary entecavir is reabsorbed by PEPT2. (C) 2013 Elsevier B.V. All rights reserved.