Effects of Rh2 on the accumulation and transport of ritonavir (RTV) in MDCK-WT and MDCK-MDR1 cells. (A) Intracellular accumulation of RTV in MDCK-WT cells treated with or without Rh2 (10 μmol/L) for 5, 15, 30, 60, 120, or 240 min. (B) Intracellular accumulation of RTV in MDCK-MDR1 cells treated with or without Rh2 (10 μmol/L) for 5, 15, 30, 60, 120, or 240 min. (C) The accumulation of RTV in MDCK-WT and MDCK-MDR1 cells in the presence of Rh2 or verapamil (Ver) for 60 min. (D) The transportation of RTV across MDCK-WT monolayer cells. (E) The transportation of RTV across MDCK-MDR1 monolayer cells. The cells were preincubated with Rh2 (1, 5, and 10 μmol/L), or Ver (100 μmol/L) for 30 min, respectively, followed by a further incubation in the presence of 2 μmol/L RTV for 60 min. The bars represent the mean±SEM of three independent experiments. bP<0.05, cP<0.01 vs control. AP, apical; BL, basolateral; Papp, apparent permeability.