The rodent Micronucleus Assay is an in vivo test for cytogenetic damage based on identification of micronuclei (MN) in the polychromatic erythrocytes (PCE) of mouse or rat bone marrow. MN are cytoplasmic chromatin masses that have the appearance of small nuclei. They arise from chromosomes that lag at anaphase due to a malfunction of the mitotic spindle or from acentric chromosomal fragments produced by clastogenesis.
MN are readily visible in anucleate erythrocytes. Immature erythrocytes are basophilic (polychromatic) for approximately 24 hours after extrusion of the nucleus; therefore, an increase in micronucleated polychromatic erythrocytes (MPCE) in treated animals is the result of MN formation occurring during exposure to a test article. Usually, a dose determination study is carried out just prior to this test for the purpose of selecting doses for the definitive evaluation.
The in vivo rodent Micronucleus Assay provides a system that includes all possible metabolic pathways available to the whole animal for absorption, distribution, metabolism and excretion of the test article. In addition, bone marrow cells provide a target removed from the major sites of metabolism; therefore, the systemic distribution of the test article or its active metabolites is required to induce MN.
Micronucleus assays have emerged as one of the preferred methods for assessing chromosome damage because they enable both chromosome loss and chromosome breakage to be measured reliably.
The rodent Micronucleus Assay is also part of the required regulatory genetic toxicology data package.
To learn more about the guidelines MicaGenix follows for this assay, visit http://www.oecd.org/dataoecd/38/58/39780112.doc
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