Dibenzothiophene sulphoxidation: a new and fast high-performance liquid chromatographic assay of mixed-function oxidation.

Dibenzothiophene (DBT) was used as a model substrate of hepatic microsomal mixed-function oxidases. Liver microsomes from Aroclor-induced rats oxidatively transformed this substrate to DBT-5-oxide and subsequently to DBT-5-dioxide. These metabolites were identified by mass spectrometry after incubation of perdeuterated DBT. A simple and fast h.p.l.c. method for determination of the metabolites using u.v. detection at 225 nm is described. Optimal reaction conditions were determined. The apparent Km and the Vmax were, respectively, 85 microM and 8.25 nmol of DBT-5-oxide/min per mg protein. The effects of the inducers phenobarbitone, 3-methylcholanthrene and DBT itself on hepatic DBT-metabolizing activity in rats were determined. DBT, an important constituent of petroleum products, might serve as a useful substrate of aromatic hydrocarbon mono-oxygenase.