An elisa assay for cytochrome P4501A in fish liver cells

An enzyme‐linked immunosorbent assay (ELISA) for measuring cytochrome P4501A (CY1A) expression in vitro in fish hepatoma cells is described. Cells were cultured as monolayers in 96–microwell cell culture plates and exposed to polychlorinated biphenyl (PCB) congeners 77, 105, 153, and 169; 3–methylcholanthrene (3–MC), and β‐naphthoflavone (BNF) for 3 d. Relative CYP1A protein content, CYP1A enzymatic activity, and total protein content were determined directly within the wells. At low concentrations of PCB 77, PCB 169, and 3–MC, the ethoxyresorufin‐O ‐ deethylase (EROD) activity was induced, but it was inhibited at high concentrations of these compounds. However, CYP1A protein content measured in an ELISA performed with intact cells increased monotonically in response to the concentration. No CYP1A induction was observed for PCB 105 and PCB 153. Because comparison between EROD activity and CYP1A amount gives information about the catalytic efficiency of CYP1A in the cells, this noncompetitive, solid‐phase ELISA is recommended as a complementary method to the EROD assay. This novel ELISA method may be an accurate in vitro technique for a rapid and sensitive screening of CYP1A‐inducible compounds.