Figure 4. Time-dependent generation of sulfated conjugate of olomoucine II in MDCKII-ABCG2 (A, D, G), MDCKII-ABCB1 (B, E, H) and MDCKII-par (C, F, I) cells and its distribution into the apical and basolateral compartments.

Relative quantification of sulfated olomoucine II was calculated as a ratio between peak area of sulfated olomoucine II and the peak area of internal standard (IS). 5 µM fumitremorgin C (FTC), a specific ABCG2 inhibitor, was used in MDCKII-ABCG2 cells for the assessment of possible involvement of ABCG2 in the transport of sulfated metabolite. 1 µM LY335979 (LY) was employed as a specific ABCB1 and endogenous canine Abcb1 inhibitor in MDCKII-ABCB1 and MDCKII-par cells, respectively. Data come from transport experiments with olomoucine II at concentrations of 100 nM (A, B, C), 1 µM (D, E, F) and 10 µM (G, H, I). In basolateral to apical transport direction, olomoucine II was added into the basolateral compartment and its sulfate conjugate was determined in the apical compartment. In the opposite transport direction, olomoucine II was applied into the apical compartment and its sulfated metabolite was analyzed in the basolateral compartment. ▴, transport into apical compartment without inhibitor; ▾, transport into basolateral compartment without inhibitor; ▵, transport into apical compartment with inhibitor; ▿, transport into basolateral compartment with inhibitor. Values are expressed as means ± SD of three independent experiments.