INVOLVEMENT OF BOTH SYN-DIHYDRODIOL-EPOXIDE AND ANTI-DIHYDRODIOL-EPOXIDE IN THE BINDING OF 7,12-DIMETHYLBENZ(A)ANTHRACENE TO DNA IN MOUSE EMBRYO CELL-CULTURES

Abstract

7,12-Dimethylbenz[a]anthracene (DMBA):deoxyribonucleoside adducts, from enzymic hydrolyses of DNA from mouse embryo cells exposed in culture to [3H]DMBA, can be separated into 2 fractions on the basis of whether or not they bind to the phenyl boronic acid residues of Servacel DHB. This suggests that these 2 fractions of adducts are derived from anti and syn bay-region dihydrodiol-epoxides, respectively. The fluorescence spectra and interactions of the major components of these 2 fractions with borate ions substantiate this interpretation. These findings indicats that both syn- and anti-dihydrodiolepoxides make a substantial contribution to DMBA binding to DNA in mouse embryo cells. For a given mouse embryo cell preparation, the relative contributions of each of these dihydrodiol-epoxides to DNA binding did not vary substantially with DMBA dose, with incubation time with DMBA, or in growing vs. confluent cultures, although there were differences between one cell preparation and another. [DMBA is a carcinogen.].