Radiosterilization of rat liver microsome containing postmitochondrial supernatant for mutation assays.

Area of Science:

• Environmental Toxicology
• Chemical Carcinogenesis
• Radiation Biology

Background:

• Metabolic activation of environmental pollutants like diesel soot and polycyclic aromatic hydrocarbons (PAHs) is crucial for understanding their mutagenicity.
• Rat liver postmitochondrial supernatant (PMS) is essential for this metabolic activation process.
• Sterilization of PMS is necessary to eliminate microbial contamination without compromising its enzymatic activity.

Purpose of the Study:

• To evaluate the efficacy of gamma irradiation as a sterilization method for rat liver PMS.
• To determine if gamma irradiation affects the metabolic activation capabilities of PMS for environmental mutagens.
• To assess the impact of gamma irradiation on PMS' s ability to activate specific compounds in different mutagenicity assays.

Main Methods:

• Rat liver PMS was subjected to gamma irradiation at -80°C with varying doses.
• Sterilizing efficacy was assessed by challenging the irradiated PMS with known numbers of Bacillus subtilis spores.
• Metabolic activation potential was tested using diesel soot, benzo(a)pyrene, fluoranthene, and dimethylnitrosamine in Salmonella typhimurium and human lymphoblast assays.

Main Results:

• A 3-Mrad dose of gamma irradiation achieved a 7.5 log kill of Bacillus subtilis spores, confirming effective sterilization.
• Irradiated PMS (3 Mrad) retained its ability to metabolically activate diesel soot, benzo(a)pyrene, and fluoranthene to mutagens in Salmonella typhimurium.
• Gamma irradiation did not impair the activation of benzo(a)pyrene to a mutagen in human lymphoblasts but reduced dimethylnitrosamine activation in S. typhimurium.

Conclusions:

• Gamma irradiation is a suitable method for sterilizing rat liver PMS for mutagenicity studies.
• A 3-Mrad dose effectively sterilizes PMS while preserving its metabolic activation capacity for key environmental mutagens.
• While generally effective, the impact of gamma irradiation on PMS activity may vary depending on the specific substrate and assay system.