[Characteristics of induced aminopyrine N-demethylase]

The study of the inducing effect of phenobarbital on the activity of N-demethylase of aminopyrine in the rat liver microsomes revealed the correlation of the rate of enzymic reaction with the changes in the maximum binding of aminopyrine by cytochrome P-450 rather than with the content of hemoprotein itself. The comparison of the activity of N-demethylation of aminopyrine in control and phenobarbital-induced rats showed the quantitative correspondence of the yield of products of the reaction--formaldehyde in the liver microsomes and 4-aminoantipyrine in the urine samples. Self-induction of N-demethylating activity at repeated aminopyrine administration to rats and the dose dependence of this phenomenon were found.