Reduction of irreversible binding of diethylstilbestrol in hamster renal cortex by inhibitors of cytochrome P-450

Hamster renal cortical slices metabolized [3H]diethylstilbestrol (DES) to reactive intermediates that irreversibly bound to macromolecules. Protein isolated from cortical slices following incubation with 50 nM [3H]DES for 90 min at 37 degrees C had 0.160 pmol [3H]DES eq/mg protein irreversibly bound. Samples of protein analyzed by gel electrophoresis revealed several radioactive peaks, indicating that specific adduct formation had occurred. No radioactivity was associated with DNA isolated from the same tissue slices. Incubation of the slices with [3H]DES under an atmosphere enriched in carbon monoxide decreased the nonextractable binding of [3H]DES metabolites to protein. The cytochrome P-450 inhibitors diethylaminoethyl 2,2-diphenylpentanoate HCl (SKF 525-A), metyrapone, butylated hydroxytoluene (BHT), and dicumarol decreased the irreversible binding of [3H]DES by 38 to 72%. Analysis of metabolites isolated from the incubation medium by high-pressure liquid chromatography indicated that carbon monoxide, BHT, and dicumarol inhibited the hydroxylation of [3H]DES. Arachidonic acid and indomethacin did not alter the irreversible binding of [3H]DES, indicating a lack of involvement of prostaglandin H synthetase in the metabolism of DES to reactive intermediates. These findings suggest that cytochrome P-450 isozymes in the hamster renal cortex metabolize DES to reactive species that covalently bind to macromolecules.