The ratio of deoxyadenosine to deoxyguanosine adducts formed by (+)-(7R,8S,9S,10R)-7,8-dihydroxy-9,10-epoxy-7,8,9,10- tetrahydrobenzo[a]pyrene in purified calf thymus DNA and DNA in V-79 cells is independent of dose.

The hypothesis that the decrease in the proportion of mutations at AT base pairs in Chinese hamster V-79 cells treated with increasing doses of (+)-(R,S,S,R)-benzo[a]pyrene diol epoxide ((+)-BPDE) is due to saturation of A for adduct formation was investigated by comparing the ratio of dA to dG adducts formed at high (0.48 microM) and low (0.04 microM) doses of [3H]-labeled (+)-BPDE. The dA to dG adduct ratio was similar in both calf thymus DNA and the genomic DNA in V-79 cells, and did not change with dose. For the V-79 cells, this ratio was also unaffected by a 24-h post treatment repair incubation.