Induction and expression of mutations at multiple drug‐resistance marker loci in Chinese hamster ovary cells
- 1 January 1983
- journal article
- research article
- Published by Wiley in Environmental Mutagenesis
- Vol. 5 (2) , 161-175
- https://doi.org/10.1002/em.2860050206
Abstract
We have observed quantitative and qualitative differences in the mutability and mutagen‐specificity of various drug‐resistance marker loci in Chinese hamster ovary (CHO) cells, which suggest that mammalian gene loci may differ in their relative mutability by a given mutagenic agent. We have used the CHO‐AT3–2 multiple‐marker mutagenesis assay system to examine the dose‐dependent induction and kinetics of expression of mutations at four well‐characterized, drugresistance marker loci, after treatment with chemical agents which produce various types of DNA damage. The CHO‐AT3–2 subline allows simultaneous quantitation and direct comparison of induced mutation frequencies at the hgprt, oua (Na+/K+ATPase), aprt, and tk loci. The agents tested in this study included ethyl methanesulfonate, methyl methanesulfonate, mitomycin C, ICR‐191, benzo[a]pyrene, and dimethylnitrosamine. The expression kinetics and optimal expression times for each drug‐resistance marker were determined in dose‐response experiments in which cells from mutagen‐treated populations were plated at 1‐2‐day intervals over a period of 10 days following mutagenesis. Comparison of induced mutation frequencies for each drug‐resistance marker after mutagen treatments yielding equivalent cell survivals (equitoxic doses resulting in relative cell survivals of 0.37) revealed locus‐specific differences in the relative mutagenicities of the agents tested. These results indicate that the apparent mutagenicity of a particular agent at a single genetic locus may not necessarily be an accurate indicator of that agent's mutagenic potential for the genome as a whole.Keywords
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