Table 1

Kinetic constants for ATP-dependent transport of LTC4 and 17β-glucuronosyl estradiol by recombinant multidrug resistance proteins Mrp2 from rat, human MRP2, and human MRP1

Recombinant TransporterKmVmax/Km
μM μl · mg protein−1 × min−1
Leukotriene C4
 Mrp2 Rat1.1  ± 0.2429
 MRP2 Human1.0  ± 0.1351
 MRP1 Human0.1  ± 0.021000
17β-Glucuronosyl estradiol
 Mrp2 Rat6.9  ± 1.816
 MRP2 Human7.2  ± 0.720
 MRP1 Human1.5  ± 0.342

ATP-dependent transport into membrane vesicles from HEK-293 cells expressing recombinant MRP2 was determined as described under Experimental Procedures. Data for recombinant MRP1 expressed in HeLa cells (Grant et al., 1994) are from our previous work (Leier et al., 1994; Jedlitschky et al., 1996). Km values were determined as the substrate concentration at half-maximal velocity of ATP-dependent transport. Data represent the mean from four determinations ± S.D.