Agonist activities of MMI metabolites at AhR in reporter gene assay. Primary human hepatocytes cultures (LH75, Hep200565, Hep200570) were incubated for 0 h and 24 h with mono-methylindoles (200 μM). Thereafter, culture medium from hepatocytes cultures was collected and applied to AZ-AHR cells for 24 h (Panels A, B, C). AZ-AHR cells were lysed and luciferase activity was measured. Data are expressed as a fold induction of luciferase activity over vehicle-treated cells and they are the mean ± SD from triplicates. Panel D: Responsivity of AZ-AHR to TCDD (24 h; 5 nM) in DMEM and ISOM culture media.