Interaction of radiation and carcinogens in the production of mutations

Studies were conducted to determine if synergistic interactions occur between radiation exposure and carcinogenic chemical treatment when given in combination. The frequency of radiation and chemically induced mutations and cell killing was determined CHO cells. The cells were exposed to 500 rad of X-rays or a single concentration of N-methyl-N'-nitro-N-nitrosoguanidine, benzo(a)pyrene, 3-methylcholanthrene, dibenzo(c,g)carbazole, alone, or in combination. For each combination of X rays and a chemical, the observed mutagenic response was less than predicted by an additive model. The mutation frequency was also measured for graded doses of 3-methylcholanthrene and X-ray exposures given alone and in combination. The data were fitted to a surface described as mutation frequency = 4.9 x 10-5 D2 + 142 C2 - 2.1 x 10-4 D2C2 where D is dose in rads and C is concentration of chemical in ug/ml. The negative interactive term indicates that over the dose range studied there was an antagonistic interaction between radiation and chemicals in production of mutations. 3 references, 3 figures