Xenobiotic-metabolizing enzymes and benzo[a]pyrene metabolism in the benzo[a]pyrene-sensitive mutant strain of Drosophila simulans

Abstract Basal levels of aryl hydrocarbon hydroxylase, epoxide hydrolase and glutathione S -transferase enzyme activities, cytochrome P-450 content and inducibility of enzymes with phenobarbital were found to be similar in the microsomes of D. simulans mutant strain 364 yv , which is sensitive to the toxic and mutagenic effects of benzo[ a ]pyrene (BP), and of the wild resistant Turku strain. In contrast, increases in the rate of BP turnover per molecule of cytochrome P-450, intensity of the hemoprotein band with apparent molecular weight 56,000 and the yield of BP 7,8-dihydrodiol and 9,10-dihydrodiol occurred only in microsomes of BP-pretreated 364 yv flies but not of Turku ones. It is likely that BP induces an aberrant form of cytochrome P-450 in 364 yv flies with a rare mutation in one of the P-450 regulating genes.