Downregulated expression of intestinal P-glycoprotein in rats with cisplatin-induced acute kidney injury causes amplification of its transport capacity to maintain "gatekeeper" function.

The expression of transporters on the apical and basal membranes of renal proximal tubular cells are down- or upregulated to various extents under cisplatin (CDDP)-induced acute kidney injury (AKI). However, little is known about the changes in transporters in tissues other than the kidney under CDDP-induced AKI. This study aimed to investigate the modulation of the expression/function of intestinal efflux transporters, P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp), in CDDP-induced AKI rats. On day 3 after the intraperitoneal administration of CDDP (5 mg/kg) to rats, the expression levels of P-gp and Bcrp were compared with those of normal rats. Further, the absorption of three P-gp substrates (6α-methylprednisolone, rhodamine 123, and gatifloxacin) was evaluated in both groups using conventional loop techniques. In the CDDP-induced AKI rats, P-gp expression in the ileum was markedly decreased to approximately 38% of that in the normal rats. However, no significant changes in Bcrp expression were observed in the AKI rats. In contrast with the reduction in P-gp expression in the AKI rats, the absorption of the three P-gp substrates remained almost the same or decreased in the AKI group. The addition of verapamil (a potent P-gp inhibitor) increased the absorption of the three P-gp substrates to the values obtained from the normal rats. In conclusion, our results suggested that P-gp expression is downregulated in rats with CDDP-induced AKI but that P-gp maintains its potency as a "gatekeeper" against the absorption of xenobiotics by amplifying its individual transport capacity under these conditions.