TY - JOUR T1 - Characterization of Methotrexate Transport and Its Drug Interactions with Human Organic Anion Transporters JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 666 LP - 671 DO - 10.1124/jpet.102.034330 VL - 302 IS - 2 AU - Michio Takeda AU - Suparat Khamdang AU - Shinichi Narikawa AU - Hiroaki Kimura AU - Makoto Hosoyamada AU - Seok Ho Cha AU - Takashi Sekine AU - Hitoshi Endou Y1 - 2002/08/01 UR - http://jpet.aspetjournals.org/content/302/2/666.abstract N2 - Life-threatening drug interactions are known to occur between methotrexate and nonsteroidal anti-inflammatory drugs (NSAIDs), probenecid, and penicillin G. The purpose of this study was to characterize methotrexate transport, as well as to determine the site and the mechanism of drug interactions in the proximal tubule. Mouse proximal tubule cells stably expressing basolateral human organic anion transporters (hOAT1 and hOAT3) and apical hOAT (hOAT4) were established. The Km values for hOAT1-, hOAT3-, and hOAT4-mediated methotrexate uptake were 553.8 μM, 21.1 μM, and 17.8 μM, respectively. NSAIDs (salicylate, ibuprofen, ketoprofen, phenylbutazone, piroxicam, and indomethacin), probenecid, and penicillin G dose dependently inhibited methotrexate uptake mediated by hOAT1, hOAT3, and hOAT4. Kinetic analysis of inhibitory effects of these drugs on hOAT3-mediated methotrexate uptake revealed that these inhibitions were competitive. TheKi values for the effects of salicylate, phenylbutazone, indomethacin, and probenecid on hOAT3-mediated methotrexate uptake were comparable with therapeutically relevant plasma concentrations of unbound drugs. In addition, in the presence of human serum albumin, the Ki values were comparable with therapeutically relevant total plasma concentrations of drugs. In conclusion, these results suggest that methotrexate is taken up via hOAT3 and hOAT1 at the basolateral side of the proximal tubule and effluxed or taken up at the apical side via hOAT4. In addition, hOAT1, hOAT3, and hOAT4 are the sites of drug interactions between methotrexate and NSAIDs, probenecid, and penicillin G. Furthermore, it was predicted that hOAT3 is the site of drug interactions between methotrexate and salicylate, phenylbutazone, indomethacin, and probenecid in vivo. The American Society for Pharmacology and Experimental Therapeutics ER -