Validation of the function of established cell lines by rhodamine 123.

<p>(<i>a</i>) Time curve of 1 µM rhodamine 123 intracellular accumulation. The intracellular accumulation of rhodamine 123 in human P-gp expressed cells was saturated after 30 minutes; therefore, the following experiments were performed after 30 minutes of incubation with rhodamine 123. (<i>b</i>) Time curve of rhodamine 123 efflux transport. After incubation with 1 µM rhodamine 123, cells were allowed to efflux rhodamine 123 at different time points. The initial rate of rhodamine 123 efflux was 10 minutes. (<i>c</i>) Concentration-dependent efflux of rhodamine 123 in wild-type P-gp. Efflux of rhodamine 123 followed Michaelis-Menten kinetics in the concentration range of0.5–30 µM. Data were presented as mean ± SE of at least three experiments, each in triplicate.