Comparative studies on the effects of various microsomal enzyme inducers on the N-demethylation of dimethylnitrosamine

The effects of various compounds on the N-demethylation of dimethylnitrosamine (DMN) were investigated and grouped into three different categories according to their effects on both DMN-demethylase I and II (using 4 and 200 mM DMN concentrations respectively). 3-Methylchol-anthrene (3-MC), β-naphthoflavone (β-NF), Aroclor 1254, benzo[a]pyrene (BP), and phenobarbital (PB) pretreatments decreased the activity of demethylase I, but they increased or had no effect on the activity of the second enzyme. Chlorpromazine pretreatment did not alter the activity of demethylase I whereas the activity of II was enhanced significantly. Feeding tryptophan and indole to rats, on the other hand, increased the activities of both demethylases as well as the cytochrome P-450 content.