We established stable human canalicular multispecific organic anion transporter (cMOAT/MRP2) cDNA transfectants, CHO/cMOAT from non-polarized Chinese hamster ovary (CHO)-K1 and LLC/cMOAT from polarized pig kidney epithelial LLC-PK1. Human cMOAT was mainly localized in the plasma membrane of CHO/cMOAT and in the apical membrane of LLC/cMOAT. The ATP-dependent uptake of leukotriene C4 (LTC4) into CHO/cMOAT membrane vesicles was enhanced compared with empty vector transfectants. Km values in CHO/cMOAT membrane vesicles were 0.24 microM for LTC4 and 175 microM for ATP. Drug sensitivity to vincristine and cisplatin in human cMOAT cDNA transfectants decreased, but not to etoposide. Cellular accumulation of vincristine and cisplatin in human cMOAT cDNA transfectants decreased, but not of etoposide. The uptake of LTC4 into CHO/cMOAT membrane vesicles was inhibited by exogenous administration of vincristine or cisplatin, but not that of etoposide. Moreover, this inhibition was more enhanced in the presence of glutathione. These consequences indicate that drug resistance to vincristine or cisplatin appears to be modulated by human cMOAT through transport of the agents, possibly in direct or indirect association with glutathione.