Comparison of DNA-repair synthesis, chromosome aberrations and induction of micronuclei in cultured human fibroblasts, Chinese hamster ovary and central mudminnow (Umbra limi) cells exposed to chemical mutagens.

In mammalian cells it has previously been observed that low DNA-repair activity is correlated with high chromosome-aberration frequency. Since fish cells typically express comparatively low amounts of DNA repair, the chromosome aberration test holds potential as a sensitive fish genotoxicity assay. A comparison of in vitro DNA-repair activity showed HF greater than CHO greater than Ul-H = Ul-F following exposure to MNNG and 4NQO. Although peak chromosome-aberration frequency varied CHO greater than Ul-H greater than HF, at comparable mutagen concentrations the relationship was Ul-H greater than HF greater than CHO following 4NQO exposure and Ul-H greater than HF = CHO after MNNG exposure. Analyzing for chromosome aberrations at high mutagen concentrations was not possible due to mitotic inhibition/toxicity which varied according to the mutagen and cell line. Micronuclei frequency varied CHO greater than Ul-H greater than HF = Ul-F. In CHO and Ul-H, a 10-15-fold increase over controls compares with only a 2-3-fold increase for HF and Ul-F. These differences are likely related, in part, to the cell-division rate of each line and the coincident repair of the damaged DNA. Reasons for the lack of negative correlation between DNA repair and chromosomal damage in fish cells are discussed.