Benzpyrene hydroxylase activity and its induction by methylcholanthrene in Morris hepatomas, in host livers, in adult livers, and in rat liver during development.

There was no consistency of the induced levels among hepatoma lines, although all the rats were sacrificed exactly 6 hr after onset of feeding under controlled dietary regimens and 24 hr after a single intraperitoneal treatment with methylcholanthrene. Benzpyrene hydroxylase in fetal rat liver was very low in activity, and after birth a marked increase was observed. After administration of methycholanthrene the fetal liver showed some increase in benzpyrene hydroxylase activities and in neonatal stages more profound responses were detect ed. The activity of benzpyrene hydroxylase and the magni tude of the induced levels in normal rat liver were completely dependent upon the age of the rat, and there were no differences in activity between male and female rats until after 21 days of age. The similarity of hepatoma lines to normal rat liver during developmental stages with respect to the activity of benzpyrene hydroxylase and its response to methylcholanthrene induction were discussed.