Alterations of microsomal monooxygenase system and carcinogen metabolism by streptozotocin-induced diabetes in rats.

The effects of diabetes on the liver microsomal monooxygenase enzymes and carcinogen metabolism have been studied in rats. Treatment with streptozotocin causes a marked enhancement in microsomal N-nitrosodimethylamine (NDMA) demethylase activity. The enhancement is due mainly to the induction of a high affinity NDMA demethylase (Km, approximately 0.05 mM) which is accompanied by the induction of a protein species with mol. wt. of 50,000. The treatment also induces aniline hydroxylase whose activity is in parallel with NDMA demethylase. Streptozotocin-induced diabetes also increases the metabolism of N-nitrosomethylethylamine but not that of N-nitrosomethylaniline or N-nitrosomethylbenzylamine. On the other hand, diabetes decreases the metabolism of benzo[a]pyrene, benzphetamine, and ethylmorphine. The result suggest that diabetes causes an alteration of the composition of cytochrome P-450 isozymes; the forms efficient in metabolizing NDMA are increased while certain other forms of cytochrome P-450 are decreased.