Figure 2.

ATP-dependent uptake of cationic drugs into membrane vesicles from MDR1- and MRP1-overexpressing cells. Uptake of [³H]-APDA (300 nM), [³H]-vincristine (300 nM) and [³H]-daunorubicin (300 nM) into membrane vesicles (50 μg) from A2780 and A2780AD cells was measured during 5 min as described under ‘experimental procedures'. Uptake into A2780AD membrane vesicles was also measured in the presence of 1 μM of the MDR1 inhibitor PSC833 (a). Similar experiments were performed with membrane vesicles from GLC₄ and from GLC₄/Adr cells either in the absence or the presence of 5 μM of the MRP1 inhibitor MK571 (b). [³H]-LTC₄ was used as control substrate for MRP1-mediated transport. Data shown are means ±s.d. from at least three experiments with at least triplicate determinations.