Inhibition of CYP1A1 catalytic activity in primary human hepatocytes by mono-methylindoles. Primary human hepatocytes from two donors (n = 2) (cultures Hep200571 and Hep220993) were pre-incubated with 5 nM TCDD for 24 h. Thereafter, mono-methylindoles (0.1 μM, 1 μM, 5 μM, 25 μM, 100 μM, 200 μM) in the mixture with specific CYP1A1 substrate luciferin-CEE were applied to the cells for 3 h. Incubations were performed in two parallel wells (technical duplicates). Bar graph shows data from culture Hep220993. The values of IC50 were calculated using data from both cultures and inserted in the figure (bottom right).