title: Mutagenicity testing in mammalian cells. I. Derivation of a Chinese hamster ovary cell line heterozygous for the adenine phosphoribosyltransferase and thymidine kinase loci.
abstract: As a first step in the development of a multiple-marker, mammalian cell mutagenesis assay system, we have isolated a Chinese hamster ovary (CHO) cell line that is heterozygous for both the adenine phosphoribosyltransferase (aprt) and thymidine kinase (tk) loci. Presumptive aprt+/- heterozygotes with intermediate levels of APRT activity were selected from unmutagenized CHO cell populations on the basis of resistance to low concentrations of the adenine analog, 8-azaadenine. a functional aprt+/  heterozygote with approximately 50% wild-type APRT activity was subsequently used to derive sublines that were also heterozygous for the tk locus. Biochemical and genetic characterization of one such subline, CHO-AT3-2, indicated that it was indeed heterozygous at both the aprt and tk loci. CHO-AT3-2 cells permitted single-step selection of mutants resistant for 8-azaadenine or 5-fluorodeoxyuridine, allowing quantitation and direct comparison of mutation induction at the autosomal aprt or tk loci, as well as in the gene involved in ouabain resistance or at the X-linked, hypoxanthine--guanine phosphoribosyltransferase (hgprt) locus. Significant dose-dependent increases in mutation frequency were observed for all 4 genetic markers after treatment of CHO-AT3-2 cells with ethyl methanesulfonate.
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000378:metabolism; D000228:Adenine Phosphoribosyltransferase / Q000235:genetics*; D000818:Animals; D006224:Cricetinae; D003412:Cricetulus / Q000235:genetics; D004351:Drug Resistance; D005020:Ethyl Methanesulfonate / Q000494:pharmacology; D005260:Female; D005467:Floxuridine / Q000378:metabolism; D006822:Hybrid Cells / Q000187:drug effects; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics; D009152:Mutagenicity Tests / Q000379:methods*; D010042:Ouabain / Q000378:metabolism; D010430:Pentosyltransferases / Q000235:genetics*; D013937:Thymidine Kinase / Q000235:genetics*
chemical_list: D005467:Floxuridine; D010042:Ouabain; D005020:Ethyl Methanesulfonate; D010430:Pentosyltransferases; D000228:Adenine Phosphoribosyltransferase; D007041:Hypoxanthine Phosphoribosyltransferase; D013937:Thymidine Kinase; D000225:Adenine; C006654:8-azaadenine