Axyl hydrocarbon hydroxylase in Morris hepatoma 5123D.

Aryl hydrocarbon hydroxylase activity in Morris hepatoma 5123D is very low, but apparently increases by the administration of 3-methylcholanthrene, as demonstrated in the host liver, small intestine, and lung from the rats bearing this tumor. The peak level of the increased activity in tumor appears 48 hr after the initial administration when the repeated treatment is given intragastrically every 24 hr. 7,8-Benzoflavone increases the enzyme activity in tumor and lung, but not in liver and small intestine. Among the subcellular fractions of the tumor cells, induction of the enzyme by 3-methylcholanthrene was observed in microsomes and nuclei, and the increased level of the activity was higher in microsomes than in nuclei.