In vivo rodent erythrocyte micronucleus assay

Area of Science:

• Toxicology and Pharmacology
• Genotoxicity Testing
• In Vivo Assays

Background:

• The in vivo micronucleus test is a widely used method for assessing the genotoxic potential of chemical substances.
• Standardized guidelines are crucial for ensuring the reproducibility and reliability of genotoxicity data generated from this assay.
• This working group aimed to provide a consensus on key parameters for conducting the in vivo micronucleus test according to OECD guideline 474.

Framework:

• The guideline covers essential aspects including the purpose, scope, relevance, application, and limitations of the test.
• It addresses the selection of appropriate species (rodents), cell populations (immature/mature erythrocytes), and the number of animals and cells per group based on statistical considerations.
• Recommendations are provided for test substance preparation, administration routes, dose levels, and treatment schedules.

Implementation:

• Analysis of immature erythrocytes in bone marrow or peripheral blood is acceptable; mature erythrocytes are acceptable in mice for longer exposure durations.
• Organic solvents like DMSO are not recommended; freshly prepared solutions/suspensions are preferred, with vegetable oils being acceptable vehicles.
• A minimum of four animals per group and 2000 cells per animal is suggested, with consideration for using both sexes if toxicity differs.

Implications:

• The guidelines ensure that genotoxicity studies are conducted with appropriate controls, including concurrent solvent (vehicle) and positive controls.
• The highest dose should be the maximum tolerated dose, with specific limit doses defined for different treatment periods.
• Adherence to these recommendations will enhance the quality and comparability of in vivo micronucleus test data for regulatory submissions and risk assessment.