AN ELISA ASSAY FOR CYTOCHROME P4501A IN FISH LIVER-CELLS

An enzyme-linked immunosorbent assay (ELISA) for measuring cytochrome P4501A (CYP1A) expression in vitro in fish hepatoma cells is described . Cells were cultured as monolayers in 96-microwell cell culture plate s and exposed to polychlorinated biphenyl (PCB) congeners 77, 105, 153 , and 169; 3-methylcholanthrene (3-MC), and beta-naphthoflavone (BNF) for 3 d. Relative CYP1A protein content, CYP1A enzymatic activity, and total protein content were determined directly within the wells. At l ow 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 meas ured in an ELISA performed with intact cells increased monotonically i n response to the concentration. No CYP1A induction was observed for P CB 105 and PCB 153. Because comparison between EROD activity and CYP1A amount gives information about the catalytic efficiency of CYP1A in t he cells, this noncompetitive, solid-phase ELISA is recommended as a c omplementary 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.