Abstract
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.
Footnotes
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This study was supported in part by grants-in-aid from the Ministry of Education, Sports, Science and Technology (11671048, 11694310, and 13671128), the Science Research Promotion Fund of the Japan Private School Promotion Foundation, and Research on Health Sciences focusing on Drug Innovation from Japan Health Sciences Foundation.
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DOI: 10.1124/jpet.102.034330
- Abbreviations:
- NSAID
- nonsteroidal anti-inflammatory drug
- OAT
- organic anion transporter
- hOAT
- human organic anion transporter
- OAT-K1
- OAT-K2, renal organic anion transporter 1 and 2
- oatp1
- oatp2, organic anion-transporting polypeptide 1 and 2
- MRP2
- multidrug resistance protein 2
- NPT1
- human type I sodium-dependent inorganic phosphate transporter
- S1
- S2, S3, the first, second, and third segment of proximal tubule
- D-PBS
- Dulbecco's modified phosphate-buffered saline
- hPAHT
- human kidneyp-aminohippurate transporter
- Received February 20, 2002.
- Accepted April 8, 2002.
- The American Society for Pharmacology and Experimental Therapeutics
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