Abstract

A single injection of morphine at a dose of 60 mg/kg produced a decrease to less than one-half of meperidine N-demethylase activity and a smaller decrease in total protein of the microsomal-supernatant fraction of rat liver. The administration of morphine by way of drinking water for 5, 10 or 18 days was also effective in decreasing the level of demethylase in rat liver. Meperidine N-demethylase activity was localized in the subfractions of liver microsomes corresponding to the "membrane" fraction.

Some evidence was found indicating that N-demethylation of morphine and meperidine may be catalyzed by rat brain preparations.