Effect of MC metabolites on EROD (CYP1A1) activities. HepG2 cells were treated with each of the MC metabolites (1 μM), i.e., 1-hydroxy-3-MC (1-OH-MC), 2-hydroxy-3-MC (2-OH-MC), 11-hydroxy-3-MC (11-OH-MC), 11,12-dihydro-11,12-dihydroxy-3-MC (MC-11,12-diol), 1-one-3-MC (MC-1-one), 11,12 epoxy-11,12 dihydro-3-MC (MC-11,12-DE), 11,12-dione-3-MC (MC-11,12-dione), and 11,12-dialdehyde-3-MC (MC-11,12-dialde). The cells were harvested after 24 h, and EROD activities were measured. Values represent mean ± S.E. (n = 3). *, statistically significant differences between MC metabolites and DMSO-treated cells at P < 0.05, as determined by Student's t test.