Electrophoretically detectable mutations induced in CHO cells by varying doses of ultraviolet radiation

Chinese hamster ovary (CHO) cells were subjected to ultraviolet radiation (UV) at doses resulting in 100% (no irradiation), 50-30%, 20-10% and approx.=1% survival. 2 divisions after UV exposure surviving cells were cloned and clones expanded for electrophoretic analysis of the products of approx.=40 enzyme loci. 4 different classes of variants (electrophoretic shifts, nulls, enzyme re-expression and enzyme modification) were detected in 29 of 1329 clones analyzed and proven mutants by subclone analysis. The frequency of mutants in the irradiated groups (28/38391 loci screened or 7.3x10-4) was significantly higher than controls. The frequency of shift mutants at 10-20% survival was higher than shifts at 30-50% survival and was significantly higher than shifts at approx.=1% survival. The frequency of nulls increased with dose. 12 of the 28 mutants obtained in the irradiated groups were at only 3 of the mean 41 loci screened/clone. (orig./AJ)