Cytotoxic and mutagenic properties of shale oil byproducts II. Comparison of mutagenic effects at five genetic markers induced by retort process water plus near ultraviolet light in chinese hamster ovary cells

A chinese hamster ovary (CHO) cell line heterozygous at the adenine phosphoribosyl transferase (APRT) locus was used for selection of induced mutants resistant to 8‐azaadenine (8AA), 6‐thioguanine (6TG), ouabain (OUA), emetine (EMT) and diphtheria toxin (DIP). The expression times necessary for optimizing the number of mutants recovered at the different loci have been determined using the know direct acting mutagen, far ultraviolet light (FUV), and a complex aqueous organic mixture (shale oil process water) activated with near ultraviolet light (NUV). Our results indicate that optimal expression times following treatment with either mutagen was between 2 and 8 days (depending on the genetic marker examined). For CHO cells treated with shale oil process water and subsequently exposed to NUV a linear dose response for mutant induction was observed for all five genetic loci. At 10% surviving fraction of cells, between 35‐ and 130‐fold increases above background mutation frequencies were observed for the various markers examined. Among the five genetic loci tested, OUA^R was the most sensitive marker tested.