Western blot analysis of ultrafine P90 effect on CYP1B1 protein in the human lung epithelial cell line Calu-3. Calu-3 cells were treated 32 h with or without P90 (32 μg/ml). Microsomal protein was isolated and the 57 kDa CYP1B1 protein was detected by a rabbit polyclonal antibody (CYP1B11-A, Alpha Diagnostic). Shown is a representative experiment out of three independent experiments. The right diagram shows the average CYP1B1 mRNA expression in Calu-3 cells after 32 h P90 treatment (n = 3, mean ± S.D.; * p < 0.05 compared to untreated cells).