Table 3.

Dissociation kinetics of [³H]-daunomycin from ABCG2^R482G containing membranes in the presence of drugs

Drug	N	koff (min−1)	FD
Control	13	0.248±0.013	0.935±0.010
Daunomycin	4	2.065±0.522a	0.970±0.004
Doxorubicin	3	3.353±0.253a	0.979±0.002
Mitoxantrone	9	0.602±0.065	0.563±0.031b
Prazosin	4	0.313±0.024	0.935±0.006
Hoechst33342	3	0.301±0.016	0.811±0.021

Membrane preparations (10 μg protein) of high five cells expressing ABCG2^R482G were incubated with [³H]-daunomycin (150–200 nM) for 2 h at 20°C to attain equilibrium binding. The membranes were diluted to 100 × volume to initiate dissociation of [³H]-daunomycin. Dissociation measurements were undertaken in the presence or absence of various compounds (30 μM). The fraction of displaced [³H]-daunomycin (F_D) and the dissociation rate constant (k_off) were determined by nonlinear regression of the Equation 4. Values represent the mean±s.e.m. from n independent observations.

^aIndicates that the k_off was different (P<0.05 ANOVA) from the control value.

^bIndicates that the F_D was different (P<0.05 ANOVA) from the control value.