Influence of monooxygenase inducers on the metabolic profile of phenanthrene in rat liver microsomes.

The oxidation of phenanthrene by rat liver microsomes significantly depends on the pretreatment of the animals as shown by means of gas chromatography/mass spectrometry. Whereas untreated animals convert phenanthrene exclusively into the 9,10-dihydrodiol (K-region), pretreatment with various polycyclic aromatic hydrocarbons and related compounds resulted in different rates of additional oxidation at the 1,2- and 3,4-position. Moreover, secondary metabolism to dihydrodiol epoxides, detected as triols, was observed. Despite considerable concentration of the proximate carcinogen of phenanthrene (1,2-dihydrodiol) only low concentrations of the ultimate carcinogen were detected which may explain the carcinogenic inefficiency of this hydrocarbon.