Comparative Metabolism of Debrisoquine, 7–Ethoxyresorufin and Benzo(a)pyrene in Liver Microsomes from Humans, and from Rats Treated with Cytochrome P–450 Inducers

: The metabolism of debrisoquine, 7–ethoxyresorufin and benzo(α)pyrene has been studied in human liver microsomes. There was a significant correlation (r = 0.70, P < 0.05) between debrisoquine hydroxylation and 7–ethoxyresorufin 0–deethylation among various livers, and debrisoquine inhibited 7–ethoxyresorufin deethylation competitively. These results suggest that debrisoquine and 7–ethoxyresorufin may be metabolised by a common P–450 form in human liver. The effect of cytochrome P–450 inducers on the metabolism of the three substrates was also examined in rat liver. Debrisoquine hydroxylation was not enhanced by phenobarbitone, β–naphthoflavone or isosafrole