Radiosterilization of rat liver microsome containing postmitochondrial supernatant for mutation assays

Gamma-irradiation was effectively employed to sterilize rat liver postmitochondrial supernatant (PMS), which is required for the metabolic activation of soots and soot-derived polycyclic aromatic hydrocarbons to mutagens. When a known number of Bacillus subtilis spores were added to the PMS and gamma-irradiated at -80 degrees C, a 2-Mrad dose resulted in a 7.5 log kill of the spores. A dose of 3 Mrads was selected as a sufficient effective sterilizing dose and had no significant effect upon the ability of gamma-irradiated PMS to metabolically activate diesel soot and two diesel soot components, benzo(a)pyrene and fluoranthene to mutagens in a Salmonella typhimurium 8-azaguanine resistance forward mutation assay. Three Mrads of gamma-irradiation also had no effect upon the ability of PMS to activate benzo[a]pyrene to a mutagen for the human lymphoblasts. However, gamma-irradiation did reduce the ability of PMS to activate dimethylnitrosamine to a mutagen for S typhimurium.