Figure 1

Concentration dependence of 20-(S)-camptothecin transport across Caco-2 cells (a), MDCK II/wild type (b), MDCK II/P-glycoprotein (c) and MDCK II/Multidrug Resistance Protein 2 (d) for apical (AP) to bisolateral (BL) transport (•) and BL to AP transport (O). Plot of effective permeability (P _eff) (mean ± standard deviation) and the best-fit line versus logarithmic concentration. Each point represents the mean (± standard deviation) for at least three observations. Michaelis–Menten parameters were determined using a weighted (1 / standard deviation) nonlinear regression and are presented in Table 1.