May 27,1975 ABSTRACT The benzo[alpyrene 45-,, 7,8-, and 9,10-ox-ides and the six corresponding phenols (4-, 7-, 9-,, and 10-hydroxybenzo[alpyrene) have' been tested for mutagenic and cytotoxic activity in bacteria and in a mammalian cell culture system. Benzo[alpyIene 4,5-oxide (K-region) was highly mutagenic in two histidine-dependent strains (TA1537 and TA1538) of Salmonella typhimurium which detect frameshift mutagens. In contrast, benzo a1pyrene 7,8-and 9,10-oxides were less than 1% as mutagenic as the 4,5-oxide. Benzo [alpyrene 7,8-and 9,10- Recent studies have indicated that much of the biologic activity of polycyclic aromatic hydrocarbons and the covalent binding of these compounds to macromolecules can be attributed to metabolic products. The end products of aromatic hydrocarbon metabolism, which include phenols, quinones, trans-dihydrodiols, and thiol conjugates, result from reactive arene oxide intermediates (1, 2). The ability of certain K-region arene oxides to bind covalently to DNA (3-5), to induce malignant transformations in cell culture (6-10), and to elicit mutations in both bacteria (11) and in cultured mammalian cells (12), suggests that arene oxides may be proximate or ultimate carcinogens of polycyclic hydrocarbons. Unfortunately, studies with arene oxides have generally been limited to the more stable K-region arene oxides.Since metabolic oxidation of polycyclic hydrocarbons occurs at multiple sites in these molecules, it is important to systematically study the biologic activity of all of the potential metabolites.In this communication, we report the mutagenic properties of the chemically synthesized 4,5-, 7,8-, and 9,10-oxides of benzo[a]pyrene (BP) and the six corresponding phenols (4-, 5-, 7-, 8-, 9-, and 10-hydroxybenzo[a]pyrene) in histidine-dependent auxotrophs of Salmonella typhimurium and in V79 Chinese hamster cells. Neither the bacteria (13) nor the V79 cells (14) contain enzymes that metabolize polycyclic hydrocarbons. We have chosen initially to study the mutagenic properties of BP derivatives because the mutation test systems are generally well characterized, relatively rapid, and provide an index of an interaction of the BP derivatives with genetic material under conditions that result in an altered phenotype.MATERIALS AND METHODS Synthesis and Handling of BP Derivatives. The unequivocal synthesis of the BP 4,5-, 7,8-, and 9,10-oxides (15, 16) and the six corresponding phenols § have been reported, as have structural proofs and criteria of purity. All compounds used in this study were greater than 98% pure. Arene oxides were dissolved in acetone/NH40H (1000:1), while BP and phepols were dissolved in acetone. Derivatives were stored at -900 in amberized glass tubes, and their stability was confirmed prior to each experiment by chromatography on silica gel thin layer sheets (Eastman 13181) using a benzene/chloroform/ethylacetate (1:1:1) solvent system. Decomposition of the arene oxides on silica gel was prevented by adding triethylamine to the solvent system (5% v/v) an...