Induction of the hepatic mixed-function oxidases by Aroclor 1254 in the hamster: comparison of Aroclor-induced rat and hamster preparations in the activation of pre-carcinogens in the Ames test.

Hepatic microsomal mixed-function oxidase activities and the metabolic activation of chemical carcinogens to mutagens in the Ames test were investigated using Aroclor 1254-induced rat and hamster preparations. Benzphetamine N-demethylase, NADPH-cytochrome c reductase and cytochromes P-450 and b5 were induced in both animals to the same extent by pre-treatment with Aroclor. However, the O-deethylation of ethoxyresorufin was markedly induced in the rat (147-fold) but only modestly in the hamster (3-fold). 1,2-Benzanthracene and 4-aminobiphenyl were more efficiently activated by the rat preparations while, in contrast, 2-acetylaminofluorene, 2-aminoanthracene, nitrosopiperidine, nitrosopyrrolidine, cyclophosphamide and phenacetin were more efficiently activated by the hamster preparations. No significant difference was observed in the activation of 3-methylcholanthrene, benzo[a]pyrene and 2-aminofluorene. It is concluded that (a) the hamster is relatively refractive to cytochrome P-448 induction, and (b) Aroclor 1254-induced rat and hamster S9 preparations differ in their ability to convert chemical carcinogens to mutagens in the Ames test.