Metabolism of 2,4-Dinitrotoluene, 2,4-Dinitrobenzyl Alcohol and 2,4-Dinitrobenzaldehyde by Rat Liver Microsomal and Cytosol Fractions

The metabolism of 2,4-dinitrotoluene (2,4-DNT), 2,4-dinitrobenzyl alcohol (2,4-DNB) and 2.4- dinitrobenzaldehyde (2,4-DNAl) in rat liver microsomal and cytosol fractions was investigated. The objectives of these studies were to determine whether 2,4-DNAl, a potent mutagen, is produced in the oxidation of 2,4-DNB to 2,4-DNBA and to clarify the nature of the enzymes responsible for the oxidation of 2,4-DNT to 2,4-DNB, 2,4-DNAl and 2,4-dinitrobenzoic acid (2,4-DNBA). Data obtained from high-performance liquid chromatography indicated that the major products of 2,4-DNT, 2,4-DNB and 2,4-DNAl in the microsomal and cytosol preparations were 2,4-DNB, 2,4-DNAl, and 2,4-DNBA and 2,4-DNB, respectively. The results indicate that 2,4-DNAl is an intermediate in the oxidation of 2,4-DNB to 2,4-DNBA. In addition, data obtained by incubating 2.4- DNT, 2,4-DNB or 2,4-DNAl with microsomal or cytosol fraction under air, nitrogen and various concentrations of CO in oxygen, using cofactors nicotinamide adenine dinucleotide phosphate and reduced nicotinamide adenine dinucleotide phosphate [NAD(P) and NAD(P)H] and inhibitors (SKF-525A, dimethyl sulfoxide, chloral hydrate, allopurinol, pyrazole and o-phenanthroline) suggest that: (a) oxidation of 2,4-DNT to 2,4-DNB is mediated by microsomal P-450; (b) oxidation of 2,4-DNB to 2,4-DNAl is mediated mainly by cytochrome P-450 and NAD-dependent alcohol dehydrogenase; (c) oxidation of 2,4-DNAl to 2,4-DNBA and reduction of 2,4-DNAl to 2,4-DNB may be mediated by NAD(P)-dependent aldehyde dehydrogenases and NAD(P)H-dependent aldehyde reductases, respectively. These results indicate that 2,4-DNT is metabolized stepwise to 2,4-DNB, 2,4-DNAl and 2,4-DNBA in the rat liver and suggest that the oxidation of 2,4-DNB to 2,4-DNAl is a metabolic activation of 2,4-DNT and that the microsomal cytochrome P-450 and alcohol dehydrogenase may play an important role in the metabolic activation of 2,4-DNT.