Changes in drug-metabolizing activities in the livers of suckling rats as a result of treatment of the lactating mothers with phenobarbitone and chlorpromazine.

1. Lactating female rats were treated with phenobarbitone or chlorpromazine. 2. Hepatic microsomal fractions from the suckling offspring were studied to see if changes had occurred in the rates of drug metabolism. 3. Treatment with phenobarbitone significantly increased the cytochrome P-450 concentration, the activity of NADPH-cytochrome c reductase (EC 1.6.2.3) and the rates of metabolism of aniline, ethylmorphine and [2-(14)C]pentobarbitone. 4. Treatment with chlorpromazine produced only small increases in the cytochrome P-450 concentration and the rate of hydroxylation of aniline.