TABLE 1

Resistance of MRP1-transfected HEK293 and HeLa cells to inorganic and methylated arsenic species

	IC₅₀ (µM) (±S.D.)		Relative Resistance^{^a}	IC₅₀ (µM) (±S.D.)		Relative Resistance^{^a}
	HEK-Vector	HEK-MRP1	Relative Resistance^{^a}	HeLa-Vector	HeLa-MRP1	Relative Resistance^{^a}
As^III	4.9 ± 1.0	25.5 ± 4.2	5.3 ± 0.9****	7.0 ± 1.2	17.5 ± 2.4	2.5 ± 0.3***
As^V	26 ± 6.7	221 ± 62	9.2 ± 3.6***	156 ± 55	303 ± 51	2.1 ± 0.5**
MMA^III	1.7 ± 0.12	3.9 ± 0.5	2.3 ± 0.2***	5.0 ± 1.2	7.6 ± 1.3	1.5 ± 0.2*
DMA^III	1.2 ± 1	1.6 ± 1.6	1.2 ± 0.2	6 ± 0.5^{^b}	7 ± 2.3^{^b}	1.2 ± 0.4^{^b}
DMA^V	1090 ± 290	1500 ± 250	1.4 ± 0.2*	690 ± 430	680 ± 450	1.0 ± 0.13

↵^a Relative resistance factors were calculated by dividing the IC₅₀ values obtained for the MRP1-expressing cell line by the IC₅₀ values obtained for empty vector expressing cell line. Values shown are the mean (±S.D.) obtained from at least three independent experiments. IC₅₀ values for the MRP1 expressing cell lines were compared with the IC₅₀ values for the empty vector control cell lines using a Student’s t test (*P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001).
↵^b Previously published in Carew et al. (2011) but done in parallel with HEK experiments.