Differences in the effect of phenobarbital treatment on the in vitro metabolism of aflatoxin and aniline by duck and rat livers

Abstract

Groups of ducks and rats were treated with phenobarbital sodium for 14 days (1 mg/ml in the drinking water) and the effects of this treatment on in vitro rates of microsomal aniline and aflatoxin metabolism were observed. Aniline hydroxylase activity was enhanced in microsomes of both species. Normal levels of activity were comparable in duck and rat livers. Aflatoxin metabolism was stimulated in crude microsomal preparations (9000 g supernatant fraction) from rat but not from duck liver. Normal mean rates of total aflatoxin metabolism were 0.31 nmole/g/min in rat liver and 47·0 nmoles/g/min in duck liver. Phenobarbital treatment had the effect of stimulating total aflatoxin metabolism, hydroxylation and demethylation in isolated rat liver microsomes. The failure of this treatment to stimulate aflatoxin metabolism in the duck liver suggested that microsomal metabolism was not rate limiting. Aflatoxin was actually metabolised 90 times more rapidly by soluble enzymes (105,000 g supernatant) from duck liver than from rat liver.