Effects of 1-nitropyrene pretreatment on the mixed-function oxidases of rat liver

The inducibility of hepatic mixed-function oxidases (MFO) was examined in adult rats following ip or dermal applications of l-nitropyrene (l-NP) at a daily dose of 30 mg/kg for 3d. The liver weights, hepatic microsomal cytochrome p-450 and b5 contents, and 7-ethoxycoumarin O-deethylase and benzopyrene hydroxylase activities of rats treated with l-NP ip were induced significantly. In contrast, hepatic aminopyrine N-demethylase activity was unaffected. Pretreatment of rats with l-NP applied on the skin did not alter significantly the liver weights and hepatic MFO activities. These results indicate that 1-NP is a 3-methyIcholanthrene-type inducer of hepatic MFO but it is not absorbed by the skin of adult rats.