Fig. 4.

A CYP3A4 activities in LS180 cells after exposure to rifampicin (open symbols) or rifabutin (filled symbols) for 24, 72, or 96 h. B CYP3A4 activities in LS180 cells after intracellular exposure to rifampicin (open symbols) or rifabutin (filled symbols) for 24 h. Data shown are the mean ± SEM of four independent biological replicates with n = 4 replicates for each concentration. The data were fitted to an E_max model (four parameter-logistic equation; variable slope); data points for rifabutin in part B were simply connected, because fitting was not possible. Individual EC₅₀ and E_max values are listed in Supplemental Material Table S6