Comparison on effects of phenobarbital and nicotine on nuclear protein synthesis in rat liver

Recently, effects on the synthesis of nuclear proteins have been reported to occur after the administration of agents which are capable of producing enzyme induction in animal cells. Bresnick [l] has reported that administration of 3-methylcholanthrene to rats produced an increase in the synthesis of a species of hepatic nuclear protein. Stein and Baserga [2] have shown that acidic nuclear protein formation was elevated in mouse salivary glands 2 hr after isoproterenol administration. In addition, an increased synthesis of specific non&stone nuclear proteins has been reported to occur in rat liver after phenobarbital injection [3] or after hydrocortisone administration [4] and in rat uterus after estradiol treatment [5]. In general, these elevations of nuclear protein formation occurred early in the induction process, e.g. prior to increases in enzyme synthesis. This evidence suggests that alteration of synthesis and turnover of specific non&stone nuclear proteins is a crucial event in activation of the flow of genetic information in mammalian cells challenged with agents that produce proliferative or enzyme inductive responses in these cells. Chronic administration of nicotine to rats in doses of 4-5 mg/kg/day has been shown to increase the activity of a number of hepatic microsomal drug metabolizing enzymes [6] . The increased activity after nicotine treatment appeared to be due to an in-