In vitro induction of cytochrome P-450 associated monooxygenase activities in primary cultures of adult rat hepatocytes

Abstract

In vitro induction of cytochrome P-450 associated monooxygenases by pehenobarbiatal(PB) and 3-methylcholanthrene(3-MC) was investigated in primary cultures of adult rat hepatocytes. 3-MC and PB were treated 24 hr often plating of hepatocytes and four monooxygenases activities were measured. 7-Ethoxycoumarin 0-deethylase and aryl hydrocarbon hydroxylase activities were increased to higher level than initial value by MC but, by PB, were increased to similar level of initial value. Biphenyl 4-hydroxylase and aminopyrine N-demethylase activities did not increased to initial level but maintenance effects could be seen. Induction pattern of PB and 3-MC was characteric. DNA repair synthesis was measured by determining $^3H$-thymidine incorporation into DNA for aflatoxin $B_1$ treated hepatocytes. Unscheduled DNA synthesis experiments were performed for untreated, PB and 3-MC treated hepatocytes. At the lower concentration of $AFB_1$, the same extent of unscheduled DNA synthesis was shown in untreated and inducer treated hepatocytes. However, at the higher concentration of $AFB_1$, in vitro administration of inducers enhanced unscheduled DNA synthesis induced by $AFB_1$. These results showed that this system may have application in the investigation of hepartocarcinogenesis by chemicals in vitro.