Table 2

Summary of amphipathic anion transport by human MRP family members

Transporter	Substrate
Transporter	Glutathione Conjugates	Glucuronate Conjugates	Monoanionic Bile Acids	Cyclic Nucleotides	Methotrexate
MRP1	⁺	⁺			⁺
MRP2	⁺	⁺			⁺
MRP3	⁺	⁺	⁺		⁺
MRP4	±	⁺		⁺	⁺
MRP5	−	−		⁺	−
MRP6	⁺	−		−	−
MRP7	⁺	⁺	−	−	−

The data from several reports describing membrane vesicle transport assays are summarized (Leier et al., 1994; Jedlitschky et al., 1996,2000; Loe et al., 1996; Chen et al., 1999, 2002; Cui et al., 1999;Kawabe et al., 1999; Zeng et al., 2000; Chen et al., 2001; Belinsky et al., 2002; Ilias et al., 2002). Membrane vesicle assays of methotrexate transport by MRP5 have not been reported. However, it is inferred from the results of the drug sensitivity analysis of MRP5-transfected cells that this compound is not a transport substrate (Wijnholds et al., 2000). Empty spaces denote compounds for which transport by the indicated pumps has not been analyzed in the literature.

−, transport not detected; +, transport detected.