Effect of P-450 inducers on glutathione (GSH) depletion by bromobenzene in primary cultures of dog hepatocytes.

Primary cultures of dog hepatocytes sensitivity responded to various inducers of cytochrome P-450; phenobarbital (PB) significantly elevated the activity of 7-ethoxycoumarin O-deethylase (ECOD) and progesterone 6 beta-hydroxylase (6 beta-OHP). beta-Naphthoflavone (beta-NF) and rifampicin (Rif) elevated the levels of 7-ethoxyresorufin O-deethylase (EROD) and 6 beta-OHP, respectively. When primary cultures of dog hepatocytes were incubated with bromobenzene, cellular reduced glutathione (GSH) levels decreased time- and dose-dependently. Pretreatment of the cultures with PB enhanced GSH depletion by bromobenzene, while beta-NF and Rif had little effect, suggesting that the 2B type cytochrome P-450 is responsible for the primary oxidation of bromobenzene to GSH-reactive metabolite(s). Bromobenzene-dependent GSH depletion was completely prevented by 10 microM SKF-525A both in the control and PB-treated primary cultures. Treatment of dog primary cultures with PB analogues also elevated the level of drug-metabolizing activity leading the cells to be more susceptible to GSH depletion by bromobenzene.