In vitro DNA-binding of microsomally-activated fluoranthene: evidence that the major product is a fluoranthene N²-deoxyguanosine adduct

Abstract

Incubation of 3-[3H]fluoranthene with a rat liver microsomal activation system in the presence of calf thymus DNA resulted in radioactivity bound to the DNA. The fluoranthene-modified DNA was enzymatically digested and a DNA adduct elution profile developed using h.p.l.c. The fraction containing the major fluoranthene--DNA adduct was further purified by h.p.l.c. and separated into two subfractions. Treatment of these with perchloric acid liberated guanine in both cases. Evidence that both were N-2 guanine derivatives was based on the pK values of these adducts determined before and after treatment with nitrous acid. The major adduct (70% of total modified deoxyribonucleosides) was further characterized by high resolution, fast atom bombardment mass spectroscopy which yielded a molecular ion consistent with a fluoranthene triol bound to the N-2 position of deoxyguanosine. Synthetic syn and anti 3-[3H]2,3-dihydroxy-1,10b-epoxy-1,2,3-trihydrofluoranthene were reacted directly with DNA and the 8-[3H]-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrofluoranthene was incubated with DNA and microsomes. The DNA from each of these reactions was enzymatically hydrolyzed and h.p.l.c. adduct profiles were developed. The major adduct formed from reaction of the anti 2,3-dihydroxy-1,10b-epoxy-1,2,3-trihydrofluoranthene with DNA and the major N-2 fluoranthene derived adduct had identical elution times on two different h.p.l.c. systems, similar pK values (before and after nitrous acid treatment) and the same u.v. spectra. In addition, derivatization of both adducts with ethyl methanesulfonate yielded identical products, as determined by h.p.l.c. analysis.

Effect of dietary fat on metabolism and DNA adduct formation after acute oral exposure of F-344 rats to fluoranthene☆

“…This diol undergoes further metabolism to form syn-and anti-FLA 2,3-diol-1,10b-epoxides. Published reports have further shown that FLA 2,3-diol-1,10b-epoxide contributes to significant DNA binding [40]. Other oxidation pathways of this diol may yield FLA 2,3-dione and FLA 7,8-diol [28].…”

Benzo(a)pyrene modulates fluoranthene-induced cellular responses in HT-29 colon cells in a dual exposure system

“…While colon cells could metabolize FLA, the generation of FLA 2,3-diol in greater proportions when cells were treated with FLA together with BaP is noteworthy due to the ability of this metabolite to bind to cellular macromolecules such as DNA and proteins (Babson et al, 1986; Hutchins et al, 1988). …”

Tumor microsomal metabolism of the food toxicant, benzo(a)pyrene, in Apc Min mouse model of colon cancer

“…While colon tumor microsomes were able to produce FLA metabolites, the generation of FLA 2, 3-diol in greater proportions in microsomal incubations of FLA with BaP assumes importance given the ability of this metabolite to bind to cellular macromolecules such as DNA and proteins [41, 42]. Therefore, it is reasonable to speculate that BaP pretreatment may enhance the generation of reactive metabolites of FLA which in a dual or sequential exposure scenario may influence tumor progression.…”