Functional analysis of rat renal organic anion transporter OAT-K1: bidirectional methotrexate transport in apical membrane

FEBS Lett. 1999 Oct 1;459(1):128-32. doi: 10.1016/s0014-5793(99)01221-1.


Renal organic anion transporter OAT-K1 was stably transfected in MDCK cells and examined for its transport characteristics and membrane localization. OAT-K1 mediated both uptake and efflux of methotrexate in the apical membranes. Immunoblotting showed that the apparent molecular mass of the expressed OAT-K1 was 50 kDa, which was comparable to that found in the rat renal brush-border membranes. The OAT-K1-mediated methotrexate transport was significantly inhibited in the presence of several organic anions such as folate and sulfobromophthalein. These findings suggest that OAT-K1 mediates bidirectional methotrexate transport across the apical membranes, and may be involved in the renal handling of methotrexate.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biological Transport
  • Carrier Proteins / genetics
  • Carrier Proteins / physiology*
  • Cell Membrane / metabolism*
  • Cells, Cultured
  • Dogs
  • Kidney / metabolism*
  • Membrane Proteins / genetics
  • Membrane Proteins / physiology*
  • Methotrexate / pharmacokinetics*
  • Microvilli / metabolism
  • Oocytes
  • Organic Anion Transporters*
  • Rats
  • Transfection
  • Xenopus


  • Carrier Proteins
  • Membrane Proteins
  • Organic Anion Transporters
  • Slc21a4 protein, rat
  • Methotrexate