fig5

Figure 5. FINs inhibit P-gp and ABCG2 transport activity. P-gp-overexpressing MDR-19 cells (A) or ABCG2-overexpressing R-5 cells (B) were incubated with 0.5 µg/mL rhodamine 123 or 15 µM purpurin-18, respectively, in the absence or presence of specific inhibitor (10 µM valspodar for P-gp and 10 µM FTC for ABCG2) or 10 µM concentrations of the FINs for 30 min after which the medium was removed and replaced with substrate-free medium with or without the inhibitor. Cells were then incubated for an additional 1 h. Inhibition of P-gp or ABCG2 was determined by calculating the fold increase in intracellular fluorescence, with fluorescence levels in cells incubated with rhodamine or purpurin-18 alone assigned a value of 1. Significance was determined from three independent experiments using a one-way ANOVA followed by a Dunnett test for multiple comparisons. Asterisks denote significant difference from the rhodamine or purpurin-18 control, where *P < 0.05, **P < 0.01, ***P < 0.001, or ****P < 0.0001. P: Purpurin-18; R: rhodamine.