Increased response of cytochrome P-450 dependent biotransformation reactions in rat liver to repeated administration of inducers.

A single intraperitoneal administration of 3-methylcholanthrene (3MC) or beta-naphthoflavone (BNF) increased aryl hydrocarbon hydroxylase (AHH) and 7-ethoxyresorufin 0-deethylase (EROD) activities. Following a second administration of both inducers 3-4 weeks later, the extent of induction was considerably greater. Such a "booster"-phenomenon was also observed with different cytochrome P-450 (P-450)-dependent N-demethylation reactions after repeated phenobarbital (PB) administrations. Again the P-450 content was higher than after a single PB administration.