Maintenance of drug-metabolizing activities by several barbiturates in primary cultures of adult rat hepatocytes

Abstract

The effects of barbiturate derivatives on drug-metabolizing enzyme activities were investigated in primary cultures of adult rat hepatocytes. All barbiturates were added into culture medium at the initiation of culture with 1 mM. And total cytochrome P-450 content and associated drug-metabolizing enzymes, such as ethoxycoumarin Odeethylase, aryl hydrocarbon hydroxylarbon hydroxylase, and aminopyrine N-demethylase were measured 24 hr after culture. Butabarbital, phenobarbital, amobarbital, mephobarbital, and hexobarbital maintained the drug-metabolizing enzyme activities to the initial level of intact cells while aprobarbital, butalbital, and pentobarbital had no effects on the enzyme activities. Secobarbital showed cytotoxic effects to hepatocytes at that concentration. To elucidate the mechanism of maintenance by hexobarbital and otherbarbiturates, the medium conditions and microsomal heme oxygenase activities were examined. Hexobarbital maintained ethoxycoumarin O-deethylase activity only in hormone supplemented medium AB. These results suggest that some components of hormone supplements may affect the transport of hexobarbital to intracellular space or the action of hexobarbital in hepatocytes. The activity of microsomal heme oxygenase was not modulated by treatment of hexobarbital, suggesting that the maintenance effects of hexobarbital was not due to the inhibition of heme oxygenase activity.