Test No. 490: In Vitro Mammalian Cell Gene Mutation Tests Using the Thymidine Kinase
The in vitro mammalian cell gene mutation test can be used to detect gene mutations
induced by chemical substances. This TG includes two distinct in vitro mammalian gene
mutation assays requiring two specific tk heterozygous cells lines: L5178Y tk+/-3.7.2C
cells for the mouse lymphoma assay (MLA) and TK6 tk+/- cells for the TK6 assay. Genetic
events detected using the tk locus include both gene mutations and chromosomal events.
Cells in suspension or monolayer culture are exposed to, at least four analysable
concentrations of the test substance, both with and without metabolic activation,
for a suitable period of time. They are subcultured to determine cytotoxicity and
to allow phenotypic expression prior to mutant selection. Cytotoxicity is usually
determined by measuring the relative cloning efficiency (survival) or relative total
growth of the cultures after the treatment period. The treated cultures are maintained
in growth medium for a sufficient period of time, characteristic of each selected
locus and cell type, to allow near-optimal phenotypic expression of induced mutations.
Mutant frequency is determined by seeding known numbers of cells in medium containing
the selective agent to detect mutant cells, and in medium without selective agent
to determine the cloning efficiency (viability). After a suitable incubation time,
colonies are counted.
Published on July 29, 2016Also available in: French
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