COMPARISON OF MOUSE AND CHICK-EMBRYO LIVE R AND HEPATOMA-CELL LINES AS MODEL SYSTEMS USED FOR ENZYMOLOGICAL ESTIMATION OF TOXICITY POTENTIALS OF ORGANIC POLLUTANTS

Cytochromes P450-dependent monooxygenase activities were determined an d compared in mouse liver microsomes and in hepatoma cell homogenates after exposure to prototype inducers of individual P450 enzymes. In vi vo inductions of levels of mouse hepatic monooxygenase activities have been found as effective biochemical markers of toxicity potentials of a series of classes of xenobiotics (CYP1A induction for toxic effects of 2,3,7,8-tetrachiorodibenzo-p-dioxin, coplanar polychlorinated biph enyls, polycyclic aromatic hydrocarbons and related pollutants; CYP2E induction for dialkyl-nitrosamines and organic solvents, e. g. acetone and ethanol; CYP2B and CYP3A induction for phenobarbital- and dexamet hasone-type of xenobiotics). A specific induction of CYP1A-dependent O -dealkylase activities by TCDD was found in Kepa-1 and Hep G2 cell cul tures, but no in vitro induction of other P450 enzymes was found after the treatment with phenobarbital, acetone or dexamethasone. Therefore , mouse liver is a suitable in vivo system for the testing of inducing effects of xenobiotics on all relevant P450 forms, while hepatoma cel l cultures are usable only for the bioassay of TCDD-like toxicity.