Phenobarbital induction of cytochrome P-450 and UDP-glucuronosyltransferase in rabbit liver plasma membranes.

The presence of cytochrome P-450 and UDP-glucuronosyltransferase was confirmed in rabbit liver plasma membranes. Their levels, expressed as amount or activity/mg protein, were 25 and 40% respectively of those found in hepatic microsomes. Both enzymes were induced by phenobarbital treatment of the animals: administration of the barbiturate for 4 days, produced a 150% increase in the cytochrome P-450 content and in the specific activity of UDP-glucuronosyltransferase. As compared with the microsomal enzymes, the plasma membrane enzymes were localized in a lipid environment characterized by high levels of cholesterol and sphingomyelin and a low level of phosphatidylcholine. Treatment with phenobarbital for 4 days also caused a significant increase of phosphatidylcholine and phosphatidylethanolamine content in plasma membranes.