Neonatal phenobarbital administration results in increased cytochrome P450-dependent monooxygenase activity in adult male and female rats.

The effects of neonatal exposure to phenobarbital during the first five days after birth on the enzymatic activity of the adult male and female rat liver P450-dependent monooxygenase system were investigated. Although liver weight per 100 grams of body weight and total hepatic microsomal protein content were not altered in adult rats treated neonatally with phenobarbital, both sexes did show significant increases in cytochrome P450 content, cytochrome P450 reductase activity, cytochrome c reductase activity, ethoxycoumarin-O-deethylase activity and in the activity of a specific glucuronyl-transferase. Several of these activities were increased to a larger extent in the females, suggesting that females may be more sensitive to this phenomenon.