[Comparison of point mutation induced by ethylnitrosourea in human fetus and Syrian hamster pulmonary epithelial cells].

Cytotoxicity and mutation at the HGPRT (hypoxanthineguanine phosphoribosyl transferase) locus induced by ethylnitrosourea (ENU) in human fetus and Syrian hamster pulmonary epithelial cells were studied. A dose-dependent relationship between ENU and both parameters was observed. Cell killing of ENU to both cell lines was similar when determined as a reduction in colony-forming efficiency. However, after treatment with 0.01 mg/ml of ENU, the frequency of point mutation was zero in the human cells, but 4.1/10(5) cells in the hamster cells. ENU at 0.8 mg/ml induced 248.4 mutants per 10(5) cells in the hamster cells, but only 9.4 mutants per 10(5) cells in the human cells. The average frequency of mutation from all doses in the hamster cells was 10.5-fold higher than in human cells. These results imply that hamster cells are more sensitive to mutation induction than human cells and the cytotoxic effect of ENU may not be responsible for point mutation in both cell lines. These results support our previous finding that human chromosomes are more stable than those of rodents.