Effects of phenobarbital and methylcholanthrene on hepatic mixed-function-oxidase activities in hamsters.

The effects of the inducers phenobarbital (PB) and 3-methylcholanthrene (MC) on hamster liver mixed-function-oxidase activities were studied. Both inducers increased to content of cytochrome P-450 in the microsomes, aminopyrine demethylase activity, and biphenyl 4-hydroxylase activity when given for 8 days. The ability of liver homogenates from treated animals to activate compounds to mutagens was tested using the Salmonella/microsome test. Neither inducer appreciably altered mutagenicity of 2-acetylaminofluorene, benzidine, benzo(a)pyrene, aflatoxin B1, or sterigmatocystin. Mutagenicity of MC was increased when homogenates from MC-treated hamsters were used as a source of activating enzymes, and this mutagenicity could be correlated with increased biphenyl 2-hydroxylase activity.