Induction of 6‐thioguanine‐resistant mutants in human diploid fibroblasts in vitro with ethylene oxide

Abstract
Human diploid fibroblasts (strain VH‐10) were exposed to the direct‐acting alkylating agent, ethylene oxide (EtO), in vitro, and the frequency of HPRT mutants was evaluated by selection in medium containing 6‐thioguanine. A dose‐dependent increase of the mutant frequency was found in the dose range of 2.5–10 mMh of EtO. The EtO‐induced mutant frequency increased 5–19 times the background frequency at low or moderately toxic doses, which indicates that EtO is a strong mutagen in human fibroblasts in vitro. The mutagenic potency was 9.8 × 10−6 per mMh.