Separation of (+)-syn-and (-)-anti-Benzo[a]pyrene Dihydrodiol Epoxide-DNA Adducts in ³²P-Postlabeling Analysis

The (+)-enantiomer of 7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (BP-7,8-diol) is a diagnostic probe for cytochrome P-450 and non-cytochrome P-450 pathways of dihydrodiol epoxidation. The principle products of epoxidation are the (+)-syn-dihydrodiol epoxide [(+)-syn-BPDE] and the (-)-anti-dihydrodiol epoxide [(-)-anti-BPDE]. Chromatographic conditions are described that separate the major deoxynucleoside 3′,5′-bisphosphate adducts derived from these dihydrodiol epoxides on commercial poly(ethylenimine) thin-layer plates. Inclusion of boric acid and magnesium chloride in the D4 solvent is a key feature of the separation. Reasonable separation of these bisphosphate adducts from the major deoxynucleoside 3′,5′-bisphosphate adduct derived from (+)-anti-BPDE is also observed. ³²P-Postlabeling analysis of DNA adducts produced following topical administration of benzo [a] pyrene to mouse skin suggests that cytochrome P-450 plays a major role in its metabolism to DNA binding derivatives.