MORPHOLOGICAL TRANSFORMATION AND DNA ADDUCT FORMATION BY DIBENZ[A,H]ANTHRACENE AND ITS METABOLITES IN C3H10T1 2CL8 CELLS/

The major routes of metabolic activation of dibenz[a,h]-anthracene (DB A) have been studied in transformable C3H10T1/2CL8 (C3H10T1/2) mouse e mbryo fibroblasts in culture. The morphological transforming activitie s of three potential intermediates formed by metabolism of DBA by C3H1 0T1/2 cells, 3,4-dihydroxy-3,4-dihydro-DBA-(DBA-(DBA-3,4-diol), trans- dihydroxy-3,4-dihydro-DBA-anti-1,2-oxide (DBA-3,4-diol-1,2-oxide) and DBA-5,6-oxide were determined. DBA-3,4-diol-1,2-oxide was a strong mor phological transforming agent giving a mean of 73% dishes with Type II or III foci and 1.63 Type II and III foci per dish at 0.5 mu g/ml. DB A-3,4-diol produced a mean of 42% dishes with Type II or III foci and 0.81 Type II and III foci per dish at 2.5 mu g/ml. DBA gave a mean of 24% dishes with Type II or III foci and 0.29 Type IT and III foci per dish at 2.5 mu g/ml. DBA-5,6-oxide was found to be inactive. DNA adduc ts of DBA, DBA-3,4-diol, DBA-3,4-diol-1,2-oxide, DBA-1,4/2,3-tetrol an d DBA-5,6-oxide in C3H10T1/2 cells were analyzed by P-32-postlabeling method. DBA gave 11 adducts, nine of which were observed in the DNA of cells treated with DBA-3,4-diol and seven from cells treated with DBA -3,4-diol-1,2-oxide. Two of these adducts that appear in each of the t reatment groups have been identified as the product of the interaction of DBA-3,4-diol-1,2-oxide with 2'-deoxyguanosine. Furthermore, there is evidence for DBA-DNA adducts in cells treated with DBA, DBA-3,4-dio l and DBA-3,4-diol-1,2-oxide arising from metabolism to (+,-)-trans,tr ans-3,4,10,11-tetrahydroxy-3,4,10,11 -tetrahydro-DBA (DBA-3,4,10,11-bi s-diol). These results are based on co-migration of C3H10T1/2 DNA addu cts with skin DNA adducts formed after topical treatment of mice with DBA-3,4,10,11-bis-diol. Tn C3H10T1/2 cells, DBA is metabolically activ ated through DBA-3,4-diol, which is further activated via the DBA-3,4- diol-1,2-oxide and DBA-3,4,10,11-bis-diol pathways. No evidence is pro vided for the metabolism of DBA by the K-region pathway.