Detection of cellular DNA adducts in human fibroblasts treated with A-ring saturated and A-NCR-DMBA

Previous reports from these laboratories revealed that 1,2,3,4-tetrahydro 7,12-dimethylbenz[a]anthracene (TH-DMBA) and 6,11-dimethylcyclopentano(a)anthracene (CP-DMA) transform human fibroblasts to an abnormal phenotype. The parent PAH 7,12-DMBA does not transform these cells. Since 7,12-DMBA but not TH-DMBA or CP-DMA is anticipated to form active bay region diol epoxides, they investigated whether the A-ring analogues form adducts with cellular DNA, when the cells are treated in S phase of the cell cycle. Treatment for 10 hr was carried out when the cells exhibited S phase entry i.e. 10 hr after Gl release from a nutritionally deficient block. Adducts were isolated using a modification of the 32P-post-labeling technique. Preliminary results indicate that TH-DMBA formed two different nucleotide adducts where as there were three different adducts identified with CP-DMA. These results suggest the level of modification to be circa 1-2 adducts/107 total nucleotides for TH-DMBA and 2-4 adducts/107 total nucleotides for CP-DMA. The present evidence accumulated to date strongly suggests that alternate mechanisms exist to oxygenate the FAH to reactive intermediates that subsequently form specific DNA adducts