July 09, 2016
The aim of the in vitro mammalian cell gene mutation test is to detect gene mutations induced by the tested item.
Many mammalian cell gene mutation systems are available, however the mouse lymphoma assay (MLA), employing the tk+/- (thymidine kinase) locus in L5178Y cells, has the advantage of detecting genetic damage ranging from single gene mutations to viable chromosomal damage affecting the tk locus. The principle of this assay is based on setting cells under selective pressure so that only mutant cells are able to survive.
Cells in suspension or monolayer culture are exposed to the test item, both with and without metabolic activation. Concurrent positive and negative controls (both with and without metabolic activation) should be used. Exposure should be for a suitable period of time (one or more cell cycles).
Cells are grown in medium with and without selective agent(s) for determination of numbers of mutants and cloning efficiency, respectively.
Cytotoxicity and viability, colony counts and mutant frequencies are determined for the cultures treated with test item and controls.
Th biological relevance of the results should be considered.
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