POLAND, ALAN P. AND DANIEL W. NEBERT: A sensitive radiameetric assay of aminopyrine N-demethylation. J. Pharmacol. Exp. Them. 184: 269-277, 1973.

A simple radiometric assay for determining aminopyrine N-demethylase activity is described. The principle of partitioning the polar“C-formaldehyde metabolite complexed with semicarbazide from the lipophilic nonmetabolized substrate(methyl-4C-labeled aminopyrine) was utilized. This radioisotopic assay correlates well with the standard colorimetric method and is at least 100 times as sensitive. Kinetic evidence for two aminopyrine N-demethylase activities is shown. With the use of this radiometric assay, a stimulation of aminopyrine N-demethylatian in fetal chick hepatic and nonhepatic tissues by prior treatment with phenobarbital, allylisopropylacetamide or 3-methylcholanthrene is detectable.