phosphorus-radioisotopes and benzotriphenylene

The binding of benzo[a]pyrene, 7,12-dimethylbenz[a]anthracene, 3-methylcholanthrene, benz[a]anthracene, dibenz[a,c]anthracene and phenanthrene to calf thymus DNA in vitro in the absence of enzymatic or chemical activation was investigated using the 32P-postlabeling assay. Reactions were performed in the dark or under white light in 1 ml of Tris-HCl buffer (pH 7.5), containing 150 mM KCl, 250 micrograms of DNA and 0.12 nmol-600 nmol of hydrocarbon. Reactions were incubated for 1 h at 37 degrees C and the extent of hydrocarbon:DNA adduct formation was determined. With the exception of phenanthrene, all of the hydrocarbons investigated formed DNA adducts that were easily detected with the 32P-postlabeling assay. The multiplicity and level of hydrocarbon:DNA adducts varied for each hydrocarbon. A dose related increase in adduct formation was observed. Adduct levels ranged from 0.07 to 15.28 adducts per 10(7) nucleotides. Highest adduct levels were detected with 7,12-dimethylbenz[a]anthracene (DMBA) and benzo[a]-pyrene (B[a]P). Hydrocarbon: DNA adduct formation was enhanced when reactions were performed under white light. A comparison of the adduct levels formed from auto-oxidation and enzymatic activation suggests that 0.05 and 0.26% of the adducts detected in the enzymatic activation of B[a]P and DMBA, can be attributed to auto-oxidation, respectively. These data demonstrate that in the absence of enzymatic or chemical activation, polycyclic aromatic hydrocarbons can undergo auto-oxidation in vitro and form hydrocarbon:DNA adducts that are detectable with the 32P-postlabeling assay.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Benz(a)Anthracenes; Benzo(a)pyrene; DNA; DNA Adducts; In Vitro Techniques; Oxidation-Reduction; Phosphorus Radioisotopes; Polycyclic Compounds

Incubation of r-1,t-2-dihydroxy-t-3,4-oxy-1,2,3,4-tetrahydrochrysene (anti-chrysene-1,2-diol 3,4-oxide), the bay-region diol-epoxide of chrysene, with rat liver microsomes in the presence of NADP+ and DNA, followed by 32P-postlabelling analysis of the DNA, revealed the presence of at least two adducts not detected when anti-chrysene-1,2-diol 3,4-oxide was incubated with DNA alone. The formation of these adducts was not blocked by the epoxide hydrolase inhibitor 1,1,1-trichloropropane-2,3-oxide. One of the adducts cochromatographed with the adduct spot obtained when authentic 9-hydroxy-r-1,t-2-dihydroxy-t-3,4-oxy-1,2,3,4-tetrahydrochrysene (anti-9-OH-chrysene-1,2-diol 3,4-oxide) was reacted with DNA. Evidence suggested that a second adduct could also be formed by further metabolism of anti-9-OH-chrysene-1,2-diol 3,4-oxide. In addition, evidence was obtained for the further metabolism of the syn-isomer of chrysene 1,2-diol 3,4-oxide and the anti-isomer of a non-bay-region diol-epoxide of dibenz[a,c]anthracene to DNA binding species, but not for that of either the anti- or syn-isomers of the bay-region diol-epoxide of benzo[a]pyrene, the anti-isomers of the bay-region or a non-bay-region diol-epoxide of benz[a]anthracene, or the anti-isomer of the bay-region diol-epoxide of benzo[b]fluoranthene.

Topics: Animals; Benz(a)Anthracenes; Chrysenes; DNA; Male; Microsomes, Liver; Phenanthrenes; Phosphorus Radioisotopes; Rats; Rats, Inbred Strains