EVALUATION OF PHENOBARBITAL BETA-NAPHTHOFLAVONE AS AN ALTERNATIVE S9-INDUCTION REGIME TO AROCLOR-1254 IN THE RAT FOR USE IN IN-VITRO GENOTOXICITY ASSAYS

A series of bacterial mutation, mammalian cell (L5178Y) gene mutation and in vitro cytogenetic assays were performed to compare the efficacy of using S9 fractions prepared from rats induced with a combination o f phenobarbital (PB) and beta-naphthoflavone (beta NF), with So fracti ons from rats treated with the general enzyme inducer Aroclor 1254. Al though some quantitative differences in the magnitudes of the mutageni c/clastogenic effects were observed between the two induction regimes, no qualitative differences were observed. The use of a combined PB/be ta NF induction regime using oral dosing is therefore considered to be a suitable substitute for Aroclor 1254.