CYTOCHROME-P450IA1 INDUCTION IN MOUSE HEPATOMA-CELL CULTURE AS AN INDICATOR OF POLYCYCLIC ORGANIC-COMPOUNDS IN FLY-ASH

The inducibility of cytochrome P450IA1 (detected as aryl hydrocarbon hydroxylase AHH and 7-ethoxyresorufin O-deethylase EROD) in the mouse hepatoma cell line Hepa-1 has been used as a bioassay for polycyclic organic compounds in fly ash samples collected from combustion of barking material, biosludge and natural gas in a fluidized bed combustor. An amount corresponding to 25 mg fly ash resulted in half of the maximal induction (ED50) of both AHH and EROD. The induction was only observed using the fly ash fraction, which contained planar aromatic compounds (PAHs, PCDDs and PCDFs, the so-called "TCDD-equivalents"). The fly ash extracts were not cytotoxic in the concentrations studied, as judged by counting viable cells or by determination of total protein content in the cultures. The Hepa-1 test, which measures induction of the cytochrome P4501A1 enzyme, seems to be a useful short-term bioassay when information about the biological response of complex environmental samples is needed.