Barbiturate N-demethylase activity in isolated rat hepatocytes.

The isolated hepatocyte preparation has become an increasingly popular system for studying xenobiotic metabolism, and there is a need for methods of determining metabolic activity. Described here is a simple and sensitive radiometric assay for barbiturate N-demethylase activity in the isolated hepatocyte suspension. The demethylation of 1,3-dimethylphenobarbital is determined by measuring the formation of its only significant metabolite, N-methylphenobarbital. The reaction is a typical P-450-mediated dealkylation.