The effects of adriamycin in vitro and in vivo on hepatic microsomal drug-metabolizing enzymes: Role of microsomal lipid peroxidation

The quinone-containing anticancer drug adriamycin augments the reduction of dioxygen to reactive oxygen species and thereby stimulates (sixfold) NADPH-dependent microsomal lipid peroxidation. In vitro the extensive adriamycin-promoted peroxidation depleted (85%) rat liver microsomal cytochrome P-450, severely inhibited cytochrome P-450-dependent monooxygenation (70%), and glucose-6-phosphatase activity (80%), and activated (450%) UDP-glucuronyltransferase activity. When lipid peroxidation was blocked by EDTA, adriamycin selectively decreased cytochrome P-450 and aminopyrine N-demethylase activity; NADPH-cytochrome c reductase, UDP-glucuronyltransferase, and glucose-6-phosphatase activities were unchanged. Washing and resedimenting peroxidized microsomes to remove adriamycin and soluble lipid peroxidation products failed to restore enzyme activities to control values. Adriamycin administered subacutely (5 mg/kg × three doses) to rats significantly descreased hepatic microsomal cytochrome P-450 content and reduced aminopyrine N-demethylase and NADPH-cytochrome c reductase activities compared to saline-treated controls. Microsomal lipid peroxidation was increased following the above adriamycin treatment. Thus, these data suggested that adriamycin was capable of impairing hepatic drug metabolism in vitro by stimulating membrane lipid peroxidation in a manner similar to carbon tetrachloride; the mechanism by which adriamycin treatment in vivo decreased the activity of the drug monooxygenase system remains unclear.