Research Article Micronuclei in Bone Marrow and Liver in relation to Hepatic Metabolism and Antioxidant Response due to Coexposure to Chloroform, Dichloromethane, and Toluene in the Rat Model Javier Belmont-Díaz, 1,2 Ana Paulina López-Gordillo, 1 Eunice Molina Garduño, 1 Luis Serrano-García, 1 Elvia Coballase-Urrutia, 3 Noemí Cárdenas-Rodríguez, 3 Omar Arellano-Aguilar, 1 and Regina D. Montero-Montoya 1 1 Departamento de Medicina Gen´ omica y Toxicolog´ ıa Ambiental, Instituto de Investigaciones Biom´ edicas, Universidad Nacional Aut´ onoma de M´ exico, Apartado Postal 70228, 04510 M´ exico, DF, Mexico 2 Departamento de Bioqu´ ımica, Instituto Nacional de Cardiolog´ ıa Ignacio Ch´ avez, Juan Badiano No. 1, Tlalpan, 14080 M´ exico, DF, Mexico 3 Laboratorio de Neuroqu´ ımica, Instituto Nacional de Pediatr´ ıa, Insurgentes Sur 3700-C, 04530 M´ exico, DF, Mexico Correspondence should be addressed to Regina D. Montero-Montoya; dorinda@unam.mx Received 28 January 2014; Accepted 24 March 2014; Published 14 May 2014 Academic Editor: Masood Ahmad Copyright © 2014 Javier Belmont-D´ ıaz et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Genotoxicity in cells may occur in diferent ways, direct interaction, production of electrophilic metabolites, and secondary genotoxicity via oxidative stress. Chloroform, dichloromethane, and toluene are primarily metabolized in liver by CYP2E1, producing reactive electrophilic metabolites, and may also produce oxidative stress via the uncoupled CYP2E1 catalytic cycle. Additionally, GSTT1 also participates in dichloromethane activation. Despite the oxidative metabolism of these compounds and the production of oxidative adducts, their genotoxicity in the bone marrow micronucleus test is unclear. Te objective of this work was to analyze whether the oxidative metabolism induced by the coexposure to these compounds would account for increased micronucleus frequency. We used an approach including the analysis of phase I, phase II, and antioxidant enzymes, oxidative stress biomarkers, and micronuclei in bone marrow (MNPCE) and hepatocytes (MNHEP). Rats were administered diferent doses of an artifcial mixture of CLF/DCM/TOL, under two regimes. Afer one administration MNPCE frequency increased in correlation with induced GSTT1 activity and no oxidative stress occurred. Conversely, afer three-day treatments oxidative stress was observed, without genotoxicity. Te efects observed indicate that MNPCE by the coexposure to these VOCs could be increased via inducing the activity of metabolism enzymes. 1. Introduction Genotoxic compounds are known to exert their efects on DNA either in a direct way or through their metabolites afer going through an enzymatic transformation. Some compounds, however, have been described as being genotoxic via alternative pathways, like the production of ROS. Tat is the case of DCM, which is primarily metabolized by CYP2E1 [1] into carbon monoxide which irreversibly binds to hemoglobin. However, under circumstances where CYP2E1 activity is inhibited or saturated it can also be metabolized into S-chloromethylglutathione by GSTT1 [2] and form DNA adducts [3]. CLF is another compound of this kind, capable of increas- ing malondialdehyde deoxyguanosine (M1dG) adducts and lipid peroxidation in HepG2 cells [4] via a CYP2E1 mediated oxidation where phosgene and, under anoxic conditions, dichloromethyl are produced [5], both being highly reactive electrophiles, able to form irreversible covalent bonds with biomolecules like lipids, proteins, and reduced glutathione (GSH) and to induce oxidative stress [6, 7]. Hindawi Publishing Corporation BioMed Research International Volume 2014, Article ID 425070, 13 pages http://dx.doi.org/10.1155/2014/425070