BACKGROUND AND PURPOSENitidine chloride (NC), a benzophenanthridine alkaloid, has various biological properties including anticancer and analgesic activities. The aim of the present study was to evaluate the role of organic cation transporter 2 (OCT2) and multidrug and toxin extrusion 1 (MATE1) in the renal disposition and nephrotoxicity of NC. EXPERIMENTAL APPROACHMDCK cells stably expressing human OCT2 and/or hMATE1 were used to investigate the OCT2-and MATE1-mediated transport of NC. In addition, the accumulation of NC and its potential toxicity were studied in rat primary-cultured proximal tubular (rPCPT) cells and in rats in vivo. KEY RESULTSNC was found to be a high-affinity substrate of both OCT2 and MATE1 with high cytotoxicity in MDCK-hOCT2/hMATE1 and MDCK-hOCT2 compared to mock cells. The OCT2 inhibitors, cimetidine and (+)-tetrahydropalmatine ((+)-THP), significantly reduced NC accumulation and cytotoxicity in MDCK-hOCT2, MDCK-hOCT2/hMATE1 and rPCPT cells. Severe kidney damage with high levels of blood urea nitrogen and lactate dehydrogenase (LDH), reduced levels of alkaline phosphatase (ALP) and pathological changes were found in rats after 20 days of successive i.v. doses of NC (5 mg·kg À1 ·day À1 ). Concomitantly, the concentration of NC in the kidney reached similar high levels at 2 h after the last dose of the 20 day treatment as those observed at 0.5 h after a single i.v. dose of 5 mg·kg À1 . CONCLUSIONS AND IMPLICATIONSOur data indicate that NC-induced nephrotoxicity might be mainly attributed to OCT2-mediated extensive renal uptake and weak tubular secretion by MATE1.Abbreviations ASP + , 4-(4-(dimethylamino)styryl)-N-methylpyridinium iodide; ESI, electrospray ionization; HPC, hydroxypropyl cellulose; MATE1, multidrug and toxin extrusion 1; MPP