Pharmaceutical Research

, Volume 25, Issue 2, pp 453–462 | Cite as

Impaired Clearance of Methotrexate in Organic Anion Transporter 3 (Slc22a8) Knockout Mice: A Gender Specific Impact of Reduced Folates

Research Paper



To elucidate the role of the renal basolateral transporter, Oat3, in the disposition of methotrexate.

Materials and Methods

Chinese hamster ovary cells expressing mouse Oat3 were used to determine kinetics and specificity of inhibition of methotrexate transport. Methotrexate clearance was then examined in vivo in wildtype and Oat3 knockout mice.


NSAIDs, ß-lactams, and uremic toxins inhibited mOat3-mediated methotrexate uptake by 70–100%, while folate, leucovorin, and 5-methyltetrahydrofolate inhibited transport by 25–50%. A K m of 60.6 ± 9.3 μM for methotrexate transport was determined. Oat3 knockout mice exhibited reduced methotrexate-to-inulin clearance ratios versus wildtype. Male wildtype mice, but not knockouts or females, demonstrated significantly accelerated methotrexate clearance in response to reduced folates. Reduced folates also markedly inhibited hepatic methotrexate accumulation in males, but not females, and the response was independent of Oat3 function.


Oat3 contributes to methotrexate clearance, but represents only one component responsible for methotrexate’s elimination. Therefore, in patients, dysfunctional hOAT3 polymorphisms or drug competition for hOAT3 transport may severely impact methotrexate elimination only when redundant means of methotrexate removal are also compromised. Furthermore, the present findings suggest that reduced-folate administration only influences methotrexate disposition in males, with the renal reduced-folate response influenced by OAT3 function.

Key words

cancer carrier chemotherapy polymorphisms renal secretion 





5-formyltetrahydrofolate (a.k.a. folinic acid or leucovorin)


5-hydroxyindoleacetic acid


Chinese hamster ovary cells transfected with empty vector


Chinese hamster ovary cells transfected with murine organic anion transporter 3


dihydroxyphenylacetic acid




the Michaelis–Menten constant




multidrug resistance-associated protein




non-steroidal anti-inflammatory drugs

OAT or Oat

human or non-human organic anion transporter, respectively




reduced folate carrier 1



This work was supported by National Institute of Diabetes and Digestive and Kidney Diseases Grant R01-DK-067216 (D.H.S.), by fellowship provisions from the American Foundation for Pharmaceutical Education (A.L.V.), and by the National Institutes of Health Grant Number C06 RR015455 from the Extramural Research Facilities Program of the National Center for Research Resources.


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Copyright information

© Springer Science+Business Media, LLC 2007

Authors and Affiliations

  1. 1.Department of Pharmaceutical SciencesMedical University of South CarolinaCharlestonUSA

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