Inducibility of rat brain drug-metabolizing enzymes

Cytochrome P450 from rat brain mitochondrial and microsomal fractions was found to be inducible by 3-methylcholanthrene, both in quantity of enzyme and in activity towards 7-ethoxyresorufin, which is a model substrate for the cytochrome P450 isoform specifically induced by 3-methylcholanthrene. Conversely, a phenobarbital treatment resulted in an induction of the microsomal cytochrome P450 only. On the other hand, the microsomal 1-naphthol-UDP-glucuronosyl transferase and epoxide hydrolase seemed to be non-inducible by 3-methylcholanthrene or by phenobarbital. The toxicological implications of these data are discussed.