Induction of Cyp1b1. YAMC cells were treated with TCDD (alone), indole-3-aldehyde (A), indole (B), indole-3-acetate (C), and tryptamine (D) alone and in combination with TCDD for 24 hours, and Cyp1b1 was determined by real-time PCR. Results are expressed as mean ± S.E. (three replicates), and significant (P < 0.05) induction (*) or inhibition (**) of TCDD-induced Cyp1b1 is indicated.