Induction of Cytochrome P-450 isoenzymes in cultured monkey hepatocytes

Abstract

The effect of phenobarbital (PB), β-naphthoflavone (β-NF) and rifampicin (Rif) on the drug-metabolizing activity of cultured squirrel monkey hepatocytes was examined. The drug metabolizing activity (e.g. alkoxycoumarin dealkylase or steroid hydroxylase) gradually decreased during the culture period with 40–70% activity remaining at 72 hr. When 0.5 mM PB was added to the culture, the activities of 7-methoxycoumarin O-demethylase (MCOD) and 7-ethoxycoumarin O-deethylase (ECOD) increased to 6–7 fold higher level than those of control at 72 hr. Testosterone 6β-hydroxylase (6β-OH-T) and testosterone 16β-hydroxylase (16β-OH-T) activities were approx. 3-fold higher than those of the control. Addition of β-NF significantly increased the activities of 7-ethoxyresorufin O-deethylase (EROD) and ECOD. Though statistically insignificant, Rif slightly increased 6β-OH-T activity. Western blot analysis indicated PB induced production of the CYP 2B and 3A subfamilies, while β-NF and Rif induced that of the CYP 1A and the CYP 3A subfamily, respectively.