CARCINOGENIC POLYCYCLIC AROMATIC HYDROCARBON-DNA INTERACTIONS IN CELL CULTURE

SAID MOHAMMED SEBTI, Purdue University

Abstract

The benzo(a)pyrene (BaP-DNA adducts formed in embryo cell cultures from rats (Fischer 344 and Wistar), mice (Balb/c and Sencar) and Syrian hamsters after various lengths of time of exposure to BaP were analyzed to investigate the mechanism of activation of BaP to DNA-binding metabolites. There were time-, species- and, to a lesser extent, strain-dependent differences in the BaP-DNA adducts formed. In cells from both Sencar and Balb/c mice, (+)7(beta),8(alpha)-dihydroxy-9(alpha),10(alpha)-epoxy,7,8,9,10-tetrahdrobenzo(a)pyrene (anti-BaPDE)-deoxyguanosine (dG) was the major BaP-DNA adduct after 5 hr of exposure to BaP whereas in cells from both Fischer 344 and Wistar rats this adduct was essentially absent. However, as the length of time of exposure to BaP increased the relative amount of the (+)anti-BaPDE-dG adduct increased in all species, and the BaP-DNA adduct profiles became more similar to one another with the (+)anti-BaPDE-dG representing the largest adduct and 7(beta),9(alpha)-dihydroxy-9(beta), 10(beta)-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene (syn-BaPDE)-dG as the other major adduct. In the mouse embryo cells, this pattern of adducts existed after 5 hr, in the hamster embryo cells by 24 hr and in Fischer 344 rat embryo cells by 48 hr. In Wistar rat embryo cells, however, other adducts remained present in larger amounts even after 96 hr. These time- and species-dependent differences in the BaP-DNA adducts were then related to mutation induction in a cell-mediated mutation assay. Analysis of the BaP-DNA adducts in target V79 cells in Syrian hamster and Wistar rat embryo cell-mediated mutation assays indicated that all reactive BaP metabolites, regardless of the relative stabilities in aqueous solution, were efficiently transferred from the activator hamster or rat embryo cells where they were formed to the target V79 cell DNA. Thus, the cell-mediated mutation assay is of value in relating BaP-DNA adducts to mutation induction in V79 cells since the adducts in these cells were representative of those in the activator cells. Analysis of the BaP-DNA adducts in V79 cells in a Wistar rat embryo cell mediated mutation assay indicated that this lesion may be of importance in the induction of mutagenesis by BaP. These studies demostrate that there are major species-specific differences in the mechanism of activation of BaP to DNA binding metabolites and that the use of embryo cell cultures from various species as activators in mutation assays provides a valid method for relating the formation of various types of BaP-DNA adducts to mutation induction.

Degree

Ph.D.

Subject Area

Biochemistry

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