OECD TG 474 is the ‘Mammalian Erythrocyte Micronucleus Test’ standard, i.e. the micronucleus test on mammalian erythrocytes, which is included in Section 4 (Health Effects) of the OECD Test Guidelines for the Testing of Chemicals. The current version of OECD Test Guideline No. 474 is an internationally recognised test method for assessing the in vivo genotoxicity potential of chemicals and other test substances.
The basic principle of the test is based on the detection of micronuclei forming in erythrocytes found in the bone marrow or in peripheral blood. Micronuclei are small, nucleus-like structures that arise during cell division from eccentric chromosome fragments or complete chromosomes arriving late, which are not incorporated into the main nucleus. The test therefore enables the detection of both clastogenic and aneugenic effects.
In the case of erythrocytes, two basic cell populations are examined:
- PCE (polychromatic erythrocytes): Young, RNA-rich, polychromatic erythrocytes
- NCE (normochromatic erythrocytes): Mature, normochromatic erythrocytes
An increase in the proportion of PCE containing micronuclei is the most important indicator of a genotoxic effect. The PCE/NCE ratio, on the other hand, provides information on a cytotoxic effect or bone marrow suppression.
The test system is usually carried out on mice or rats. Bone marrow and/or peripheral blood may be used for this purpose. As in rats, erythrocytes with micronuclei in peripheral blood can be rapidly cleared by the spleen, the examination of bone marrow may be more suitable; in mice, the use of peripheral blood is widespread. The analysis can be carried out microscopically or by flow cytometry.
Why is it carried out?
OECD TG 474 is being carried out for the following scientific and regulatory purposes:
Identification of genotoxic hazards: determination of the test substance’s potential to cause damage to chromosome structure or chromosome number
Evidence of clastogenic and aneuogenic effects: assessment of chromosome breaks and changes in chromosome number under in vivo conditions
Validation of in vitro test results: in vivo follow-up of substances that have produced positive or suspicious results in in vitro genotoxicity tests
Support for regulatory documentation: Use in safety assessments of chemicals, medicinal products, pesticides, biocidal products, medical devices and biotechnological products
Contribution to risk assessment: Interpretation of genotoxic risk in relation to exposure scenarios
- Product safety and quality assurance: Documentation of the biosafety profile of raw materials, intermediates or finished products
OECD TG 474 is not a stand-alone carcinogenicity test. It is designed to identify a genotoxic risk; the results must be interpreted in conjunction with other genotoxicity tests, physicochemical data and an exposure assessment.
As part of our nano-testing services, we carry out investigations in accordance with OECD TG 474 with scientific rigour, drawing on our accredited laboratory facilities and our quality management system. Our scope of services includes the following:
Study design and protocol development
- Preparation of a test report in accordance with OECD TG 474
- Determination of the dosage range and definition of the main experimental design in accordance with the physicochemical properties of the test substance
- Determination of negative controls, solvent controls and suitable positive control groups
- Scientific justification for the routes of administration, dosages and sampling times
- Compliance with ethical approval and animal welfare requirements
For further information on experimental design, sample acceptance criteria and reporting procedures for your studies in accordance with OECD TG 474, please feel free to contact Nano-Test.