Effects of AhR siRNA on AhR Protein Expression in HUVECs and HUAECs. HUVECs (A) and HUAECs (B) were treated with the transfection reagent (vehicle) or transfected with the scrambled (ssiRNA, 20 nM) or AhR siRNA (siRNA, 20 nM) for 2, 4, or 6 days. Proteins were subjected to Western blotting to determine the degree of AhR knock down. Data are expressed as means ± SEM fold of the vehicle (Veh, n =4). *Differ from the vehicle (Veh) (p < 0.05).