INDUCTION OF CYTOCHROME P-448 BY 3-METHYLCHOLANTHRENE IN THE RAT DURING INHIBITION OF PROTEIN SYNTHESIS IN VIVO

Administration of cycloheximide in vivo during induction of rats with 3-methylcholanthrene prevents the increase in total cytochrome P-450 content usually seen under the influence of the inducer. The population of cytochromes P-450 in the livers of these animals is, however, similar to that in the completely induced animals. Microsomal aryl hydrocarbon hydroxylase activity and biphenyl-2-hydroxylation are enhanced severalfold and biphenyl-4-hydroxylation is enhanced twofold. Monooxygenase activity shows the same pattern of preferential inhibition as in microsomes from animals which had received the inducer only. The affinity of the reduced cytochromes for the ligand metyrapone is considerab…