Mutagenesis Testing with Mammalian Cells: Validating and Adapting a Multiple-Marker Bioassay to Activate and Detect Mutagens in Crude Samples for Energy Technology. Progress Report, July 1975-September 1980

摘要

The Chinese hamster ovary (CHO) assay developed during this period offers the unique capability of measuring forward mutation at four gene loci within a single cell line - the autosomal adenine phosphoribosyltransferase (aprt) and thymidine kinase (tk) loci quantified by mutant resistance to azaadenine and fluorodeoxyuridine, as well as the genes involved in resistance to ouabain (Na-K-ATPase) and thioguanine (hypoxanthine-guanine phosphoribosyl transferase, hgprt). This multiple-marker system combines and expands the attributes of the two major mammalian mutagenesis assays currently in use: CHO systems employing the single-locus hgprt assay and mouse L5178Y systems assaying mutation only at the tk locus. Extensive validation carried out during the course of this study indicates that using a combination of loci may increase the reliability and generality of in vitro mammalian mutagenesis assays to detect a variety of mutagens. In particular, the aprt locus offers rapid expression kinetics and minimal technical problems with cell density artifacts and dilution procedures and provides a data base obtained with a known marker for single gene mutation. Preliminary evidence from experiments with plant flavonols suggests that these clastogens producing chromosome aberrations and tetraploidy are detected as mutagens at the tk locus but not at the other three markers. The rapid expression of tk mutants and the possibility that this locus detects a broader spectrum of genetic lesions than do the other markers argues for using tk and aprt loci in combination. (ERA citation 06:003026)