Rk. Sindhu et Y. Kikkawa, METABOLISM OF (-TRANS-BENZO[A]PYRENE-7,8-DIHYDRODIOL BY 3-METHYLCHOLANTHRENE-INDUCED RAT-LIVER HOMOGENATES()), Toxicology letters, 81(1), 1995, pp. 5-13
Using a new sensitive reverse-phase HPLC assay with on-line radioactiv
ity detector, metabolism of (+)-transbenzo[a]pyrene-7,8-dihydrodiol (B
[a]P diol) to the ultimate carcinogen benzo[a]pyrene-7,8-diol-9,10-epo
xide (B[a]PDE) was studied using 3-methylcholanthrene-induced rat live
r homogenates. The results demonstrate that the stereoselectivity of B
[a]PDE formation is a function of the concentration of the cellular co
nstituents in the incubation media. At more dilute concentrations of t
he homogenate, the ratio of anti- to syn-B[a]PDE was the highest and d
ecreased as the homogenate protein was increased in the incubation med
ium. However, there was a marked and parallel decrease of free B[a]PDE
and DNA-bound radioactivity with increasing concentrations of cellula
r constituents in the incubation medium. The decreased DNA-bound radio
activity appears to be due to the preferential binding of B[a]PDE to g
lutathione and to proteins as the homogenate concentration was increas
ed in the incubation media. These results indicate that liver homogena
tes, while apparently preserving the function of microsomes, present a
dditional opportunities to study the interrelationship among cytochrom
e P450 monooxygenase activity, water-soluble conjugates, and binding o
f B[a]P diol metabolites to macromolecules in the study of benzo[a]pyr
ene-induced carcinogenesis.