Basal and TCDD-inducible expression of Cyp1a/CYP1A in tissues from WT, Cyp1a KO, and hCYP1A1/1A2 mice. Microsomes were prepared from vehicle (corn oil) and TCDD-treated hCYP1A1/1A2, Cyp1a KO, and WT mice from the tissues shown and immunoblotted for hCYP1A1 (A and D), human CYP1A2 (B), and mouse Cyp1a (C) as detailed in Materials and Methods. Standards: CYP1A1 (0.36 pmol/lane) and CYP1A2 (1 pmol/lane) expressed in bacterial membranes.