Xenobiotic biotransformation in wild birds: activity, induction, characterization and comparison with rat and mouse microsomal enzymes.

1. Benzo[a]pyrene hydroxylase, aminopyrine demethylase and glutathione S-transferase activities in hepatic and extrahepatic tissues of five wild birds, rat and mouse were compared. 2. Hepatic benzo[a]pyrene hydroxylase of wild pigeon was at least three times higher than that of rat or mouse. Hepatic aminopyrine demethylase and GSH S-transferase activities of wild birds were lower than those of rodents. 3. Renal GSH S-transferase of wild birds was 2-3 times more than in rat and mouse. 4. Avian benzo[a]pyrene hydroxylase activity of hepatic and renal tissue was linear up to 3.0 mg enzyme protein with pH optima of 7.4 and 7.2, at 42 degrees C. Apparent Km values were 11.76 and 3.33 microM respectively. 5. Hepatic enzyme activity was induced four-fold by 3-methylcholanthrene and about two-fold by phenobarbitone administration.