Formation of DNA adducts from oil-derived products analyzed by P-32-HPLC

The aim of this study was to investigate the genotoxic potential of DNA add ucts and to compare DNA adduct levels and patterns in petroleum vacuum dist illates, coal tar distillate, bitumen fume condensates, and related substan ces that have a wide range of boiling temperatures. An in vitro assay was u sed for DNA adduct analysis with human and rat S-9 liver extract metabolic activation followed by P-32-postlabeling and P-32-high-performance liquid c hromatography (P-32-HPLC). For petroleum distillates originating from one c rude oil there was a correlation between in vitro DNA adduct formation and mutagenic index, which showed an increase with a distillation temperature o f 250 degreesC and a peak around a distillation point of approximately 400 degreesC. At higher temperatures, the genotoxicity (DNA adducts and mutagen icity) rapidly declined to very low levels. Different petroleum products sh owed a more than 100-fold range in DNA adduct formation, with severely hydr otreated base oil and bitumen fume condensates being lowest. Coal tar disti llates showed ten times higher levels of DNA adduct formation than the most potent petroleum distillate. A clustered DNA adduct pattern was seen over a wide distillation range after metabolic activation with liver extracts of rat or human origin. These clusters were eluted in a region where alkylate d aromatic hydrocarbons could be expected. The DNA adduct patterns were sim ilar for base oil and bitumen fume condensates, whereas coal tar distillate s had a wider retention time range of the DNA adducts formed. Reference sub stances were tested in the same in vitro assay. Two- and three-ringed nonal kylated aromatics were rather low in genotoxicity, but some of the three- t o four-ringed alkylated aromatics were very potent inducers of DNA adducts. Compounds with an amino functional group showed a 270-fold higher level of DNA adduct formation than the same structures with a nitro functional grou p. The most potent DNA adduct inducers of the 16 substances tested were, in increasing order, 9,10-dimethylanthracene, 7,12-dimethylbenz[a]anthracene and 9-vinylanthracene. Metabolic activation with human and rat liver extrac ts gave rise to the same DNA adduct clusters. When bioactivation with mater ial from different human individuals was used, there was a significant corr elation between the CYP 1A1 activity and the capacity to form DNA adducts. This pattern was also confirmed using the CYP 1A1 inhibitor ellipticine. Th e P-32-HPLC method was shown to be sensitive and reproducible, and it had t he capacity to separate DNA adduct-forming substances when applied to a gre at variety of petroleum products.