Effect of donor age on the levels of activity of rat, hamster and human liver S9 preparations in the Salmonella mutagenicity assay.

Liver S9 fractions were prepared from male and female Syrian Golden hamsters and Sprague-Dawley rats, 1, 3, 6 and 12 months of age, which were either uninduced (corn-oil treated) or induced with Aroclor 1254 suspended in corn oil. These preparations were compared at varying protein levels for their ability to metabolize polycyclic aromatic hydrocarbons (benzo(a)pyrene, 3-methylcholanthrene, 7,12-dimethylbenzanthracene), aromatic amines (N-2-acetyl-aminofluorene, beta-naphthylamine, benzidine), and nitroso compounds (N-nitroso-diethylamine, nitrosopyrrolidine, nitrosodiethylmethylurea) to products mutagenic to Salmonella typhimurium. With 3-methylcholanthrene or benzo(a)pyrene in the presence of S9 preparations from Aroclor-treated male rats, the numbers of revertant colonies decreased with increasing age of the animals. Mutagenicity of aromatic amines was not affected by the age of the donor animals from which the S9 was prepared. The use of liver S9 from 1-month-old hamsters produced the highest number of revertant colonies with nitrosodiethylamine. This number decreased with preparations from animals of increasing age. The greatest number of revertant colonies with nitrosopyrrolidine occurred with preparations from male hamsters. A decrease in numbers of revertant colonies with increasing age was observed with the S9 preparation from Arcolor-treated male rats. Nitroso-diethylmethylurea was mutagenic only in the presence of S9 from male or female Aroclor-treated hamsters and the metabolic activity of the S9 preparations did not change with age. S9 preparations from livers of 50-70-year-old humans were compared for their ability to produce mutagenic metabolites at a number of protein levels.(ABSTRACT TRUNCATED AT 250 WORDS)