The induction of microsomal hydroxylases in regenerating rat liver

1,2-Benzanthracene increases the aryl hydrocarbon hydroxylase activity in regenerating rat liver microsomal preparations up to 20-fold compared to a 5-fold increase in estrogen hydroxylase activity. In normal liver a 4-fold increase in aryl hydrocarbon hydroxylase but no change in estrogen hydroxylase is observed. The optimum dose of 1,2-benzanthracene is 75–100 mg/kg body weight, with an induction time of 10 h for both activities. Actinomycin D or puromycin inhibits 50% of the aryl hydrocarbon hydroxylase and 100% of the estrogen hydroxylase inductions. It is suggested that there are different induction mechanisms for these two components of the microsomal hydroxylase complex.