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Archives of Toxicology (v.85, #8)

Alternatives to animal testing: current status and future perspectives by Manfred Liebsch; Barbara Grune; Andrea Seiler; Daniel Butzke; Michael Oelgeschläger; Ralph Pirow; Sarah Adler; Christian Riebeling; Andreas Luch (pp. 841-858).

On the occasion of the 20th anniversary of the Center for Alternative Methods to Animal Experiments (ZEBET), an international symposium was held at the German Federal Institute for Risk Assessment (BfR) in Berlin. At the same time, this symposium was meant to celebrate the 50th anniversary of the publication of the book “The Principles of Humane Experimental Technique” by Russell and Burch in 1959 in which the 3Rs principle (that is, Replacement, Reduction, and Refinement) has been coined and introduced to foster the development of alternative methods to animal testing. Another topic addressed by the symposium was the new vision on “Toxicology in the twenty-first Century”, as proposed by the US-National Research Council, which aims at using human cells and tissues for toxicity testing in vitro rather than live animals. An overview of the achievements and current tasks, as well as a vision of the future to be addressed by ZEBET@BfR in the years to come is outlined in the present paper.

Keywords: Alternatives to animal testing; ZEBET; 3Rs; Replacement; Reduction; Refinement

Bile acids as colon carcinogens and coffee ingredients as antagonists by H. M. Bolt; R. Marchan; J. G. Hengstler (pp. 859-860).

A comprehensive review about micronuclei: mechanisms of formation and practical aspects in genotoxicity testing by H. M. Bolt; J. D. Stewart; J. G. Hengstler (pp. 861-862).

Carcinogenicity of deoxycholate, a secondary bile acid by Carol Bernstein; Hana Holubec; Achyut K. Bhattacharyya; Huy Nguyen; Claire M. Payne; Beryl Zaitlin; Harris Bernstein (pp. 863-871).

High dietary fat causes increased bile acid secretion into the gastrointestinal tract and is associated with colon cancer. Since the bile acid deoxycholic acid (DOC) is suggested to be important in colon cancer etiology, this study investigated whether DOC, at a high physiologic level, could be a colon carcinogen. Addition of 0.2% DOC for 8–10 months to the diet of 18 wild-type mice induced colonic tumors in 17 mice, including 10 with cancers. Addition of the antioxidant chlorogenic acid at 0.007% to the DOC-supplemented diet significantly reduced tumor formation. These results indicate that a high fat diet in humans, associated with increased risk of colon cancer, may have its carcinogenic potential mediated through the action of bile acids, and that some dietary anti-oxidants may ameliorate this carcinogenicity.

Keywords: Colon cancer; Deoxycholate; Adenocarcinoma; Chlorogenic acid

The in vitro MN assay in 2011: origin and fate, biological significance, protocols, high throughput methodologies and toxicological relevance by Micheline Kirsch-Volders; Gina Plas; Azeddine Elhajouji; Magdalena Lukamowicz; Laetitia Gonzalez; Kim Vande Loock; Ilse Decordier (pp. 873-899).

Micronuclei (MN) are small, extranuclear bodies that arise in dividing cells from acentric chromosome/chromatid fragments or whole chromosomes/chromatids lagging behind in anaphase and are not included in the daughter nuclei at telophase. The mechanisms of MN formation are well understood; their possible postmitotic fate is less evident. The MN assay allows detection of both aneugens and clastogens, shows simplicity of scoring, is widely applicable in different cell types, is internationally validated, has potential for automation and is predictive for cancer. The cytokinesis-block micronucleus assay (CBMN) allows assessment of nucleoplasmic bridges, nuclear buds, cell division inhibition, necrosis and apoptosis and in combination with FISH using centromeric probes, the mechanistic origin of the MN. Therefore, the CBMN test can be considered as a “cytome” assay covering chromosome instability, mitotic dysfunction, cell proliferation and cell death. The toxicological relevance of the MN test is strong: it covers several endpoints, its sensitivity is high, its predictivity for in vivo genotoxicity requires adequate selection of cell lines, its statistical power is increased by the recently available high throughput methodologies, it might become a possible candidate for replacing in vivo testing, it allows good extrapolation for potential limits of exposure or thresholds and it is traceable in experimental in vitro and in vivo systems. Implementation of in vitro MN assays in the test battery for hazard and risk assessment of potential mutagens/carcinogens is therefore fully justified.

Keywords: Micronuclei; Cytokinesis-block micronucleus assay; Genotoxicity

NF-E2-related factor 2 activation in PC12 cells: its protective role in manganese-induced damage by Huangyuan Li; Siying Wu; Nian Shi; Wei Lin; Junyi You; Wenhua Zhou (pp. 901-910).

Manganese neurotoxicity presents with Parkinson-like symptoms that are associated with the generation of reactive oxygen species. Thus, its occurrence and severity can be reduced by cellular antioxidants. The components of the transcription factor NF-E2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway are the central regulators of cellular antioxidant responses. In this study, we investigated the role of activation of Nrf2 in response to oxidative damage induced by manganese chloride (MnCl₂) in rat adrenal pheochromocytoma (PC12) cells. Exposure of PC12 cells to MnCl₂ for 24 h promoted an increased cytosolic and nuclear accumulation of Nrf2 and enhanced the binding of Nrf2 to the HO-1 gene ARE, thereby inducing the expression of an Nrf2-regulated gene, HO-1. Pre-treatment with tert-butylhydroquinone (tBHQ), a known agent that activates the Nrf2/ARE-HO-1 pathway, for 16 h prior to the 24 h MnCl₂ exposure attenuated both the cytotoxicity and the apoptosis induced by MnCl₂. These protective effects of tBHQ indicated a protective role for Nrf2 against MnCl₂-induced cell damage. Taken together, these findings suggest that Nrf2 may play an important role in the protection of PC12 cells against MnCl₂ neurotoxicity.

Keywords: NF–E2-related factor 2 (Nrf2); Heme oxygenase-1 (HO-1); Apoptosis; Manganese chloride; tert-Butylhydroquinone (tBHQ)

Effect of methylmercury administration on choroid plexus function in rats by Masaaki Nakamura; Akira Yasutake; Masatake Fujimura; Noriyuki Hachiya; Masumi Marumoto (pp. 911-918).

Methylmercury (MeHg) is a well-known environmental neurotoxin. The choroid plexus (CP), the main component of the blood–cerebrospinal fluid (CSF) barrier (BCSFB), protects the brain from xenobiotics, similar to the blood–brain barrier. Because CP is considered a critical target site of MeHg-induced neurotoxic damage, functional alterations in CP may be caused in relation to the extent of MeHg-induced brain injury. To test this hypothesis, we examined time-dependent pathological alterations in rats administered subtoxic (asymptomatic group) or toxic (symptomatic group) MeHg doses for 3 weeks after the cessation of MeHg administration. We primarily assessed (1) mercury concentrations in the brain, CSF, and plasma; (2) histopathological changes in the brain; (3) albumin CSF/plasma concentration quotient (Q_alb), an index of BCSFB dysfunction; and (4) concentration of CSF transthyretin (TTR), which is primarily produced in CP. Mercury concentrations in the brain, CSF, and plasma decreased, and Q_alb and CSF TTR concentrations did not change significantly in the asymptomatic group. In the symptomatic group, brain and CSF mercury concentrations did not decrease for 2 weeks after the cessation of MeHg administration, but no pathological alteration occurred in the brain during this period. Pathological changes in the cerebellum became evident 3 weeks after the cessation of MeHg administration. Furthermore, Q_alb continued to increase after the cessation of MeHg administration, whereas no decrease in CSF TTR concentration was observed, indicating selective impairment of CP function. These findings suggest that MeHg at toxic doses causes selective functional alteration of CP before leading to pathological alterations in the brain.

Keywords: Methylmercury; Choroid plexus; Cerebrospinal fluid; Q_alb ; Transthyretin

Induction of epoxide hydrolase and glucuronosyl transferase by isothiocyanates and intact glucosinolates in precision-cut rat liver slices: importance of side-chain substituent and chirality by Ahmad Faizal Abdull Razis; Manuela Bagatta; Gina Rosalinda De Nicola; Renato Iori; Costas Ioannides (pp. 919-927).

The potential of three isothiocyanates, namely R,S-sulforaphane, erucin and phenethyl isothiocyanate, of two naturally occurring glucosinolates, namely glucoerucin and glucoraphanin, and of the enantiomers of sulforaphane to modulate glucuronosyl transferase and epoxide hydrolase, two major carcinogen-metabolising enzyme systems, was investigated in precision-cut rat liver slices. Following exposure of the slices to the isothiocyanates (0–25 μM), erucin and phenethyl isothiocyanate, but not R,S-sulforaphane, elevated glucuronosyl transferase and epoxide hydrolase activities and expression, determined immunologically. Of the two enantiomers of sulforaphane, the R-enantiomer enhanced, whereas the S-enantiomer impaired, glucuronosyl transferase activity and only the former increased protein expression; furthermore, R-sulforaphane was more effective than the S-enantiomer in up-regulating microsomal epoxide hydrolase. When precision-cut rat liver slices were exposed to the same concentrations of glucoerucin and glucoraphanin, both glucosinolates caused a marked increase in the activity and expression of the microsomal epoxide hydrolase but had no effect on glucuronosyl transferase activity. It may be inferred that the ability of isothiocyanates to enhance hepatic microsomal epoxide hydrolase and glucuronosyl transferase activities is dependent on the nature of the side chain. Moreover, in the case of sulforaphane, the naturally occurring R-enantiomer increased both activities, whereas, in contrast, activities were impaired in the case of the S-enantiomer. Finally, intact glucosinolates are potent inducers of epoxide hydrolase and can thus contribute directly to the chemopreventive potential associated with cruciferous vegetable consumption.

Keywords: Isothiocyanates; Glucosinolates; Sulforaphane; Glucoraphanin; Phenethyl isothiocyanate; Erucin

Structural isomerization of synephrine influences its uptake and ensuing glutathione depletion in rat-isolated cardiomyocytes by Luciana Grazziotin Rossato; Vera Marisa Costa; Paula Guedes de Pinho; Félix Carvalho; Maria de Lourdes Bastos; Fernando Remião (pp. 929-939).

Synephrine is a natural compound, frequently added to ephedra-free dietary supplements for weight-loss, due to its effects as a nonspecific adrenergic agonist. Though only p-synephrine has been documented in plants, the presence of m-synephrine has also been reported in weight-loss products. The use of synephrine in dietary supplements was accompanied by reports of adverse effects, especially at the cardiovascular level. It is well known that the imbalance in cardiac glutathione levels can increase the risk of cardiomyopathy. The present work aimed to study the role of organic cation-mediated transport of m- and p-synephrine and the possibility that p- and m-synephrine induce intracellular changes in glutathione levels in calcium-tolerant freshly isolated cardiomyocytes from adult rat. After a 3 h incubation with 1 mM p- or m-synephrine, the intracellular content of synephrine was measured by gas chromatography/ion trap-mass spectrometry (GC/IT-MS); cell viability and intracellular glutathione levels were also determined. To evaluate the potential protective effects of antioxidants against the adverse effects elicited by m-synephrine, cells were pre-incubated for 30 min with Tiron (100 μM) or N-acetyl-cysteine (NAC) (1 mM). To assess the influence of α₁-adrenoceptors activation in glutathione depletion, a study with prazosin (100 nM) was also performed. The results obtained provide evidence that organic cation transporters OCT3 and OCT1 play a major role in m- and p-synephrine-mediated transport into the cardiomyocytes. The importance of these transporters seems similar for both isomers, although p-synephrine enters more into the cardiomyocytes. Furthermore, only m-synephrine induced intracellular total glutathione (GSHt) and reduced glutathione (GSH) depletion. NAC and Tiron were able to counteract the m-synephrine-induced GSH and GSHt decrease. On the other hand, the incubation with prazosin was not able to change m-synephrine-induced glutathione depletion showing that this effect is independent of α₁-adrenoceptor stimulation. In conclusion, both positional isomers require OCT3 and OCT1-mediated transport to enter into the cardiomyocytes; however, the hydroxyl group in the p-position favours the OCT-mediated transport into cardiomyocytes. Furthermore, the structural isomerization of synephrine influences its toxicological profile since only m-synephrine caused GSH depletion.

Keywords: Synephrine; Phenylephrine; Rat cardiomyocytes; Organic cation transporter; Glutathione depletion

Purification and characterization of a cytotoxic neurotoxin-like protein from Naja haje haje venom that induces mitochondrial apoptosis pathway by Amr E. El Hakim; Amira M. Gamal-Eldeen; Yasser E. Shahein; Nahla M. Mansour; Ahmed F. Wahby; Amira M. K. Abouelella (pp. 941-952).

This study reported the purification and characterization of a cytotoxic, neurotoxin-like protein derived from the venom of the Egyptian cobra Naja haje haje, Elapidae family, and explored their mechanistic role in the cell death. The protein purification was performed through ion-exchange chromatography and gel-filtration chromatography and was characterized by SDS–PAGE, amino acid sequencing, and mass spectrum analysis. The antitumor activity of Naja haje venom (NHV) and its fractions (NHVI, NHV-Ia, NHV-Ib, NHV-Ic, NHV-II, NHV-III, and NHV-IV) were tested against different human cancer cell lines. The molecular cascade of cell death was explored through evaluation of apoptosis/necrosis ratio, DNA fragmentation, histone deacetylase (HDAC) activity, mitochondrial transmembrane potential (Δψ_m), cytochrome c release, total caspases, caspase-3, caspase-9, and cell cycle analysis by flow cytometry. Most of the separated fractions possessed variable cytotoxic effect against different cancer cells. The most potent antitumor fraction was NHV-Ic due to its ability to induce DNA damaging and fragmentation that was associated with a significant induction of apoptosis via mitochondrial pathway and disturbed cell cycle phases as well as an inhibition of HDAC activity. NHV-Ic induced the mitochondrial pathway initially by the impairment of Δψ_m besides the DNA damage and in response to that the mitochondria-released cytochrome c that may in turn activated total caspases, caspase-3 and caspase-9 in lymphoblastic leukemia 1301 cells. The partial amino acid sequencing of NHV-Ic revealed 100, 95.65, and 91.3% homology with the Long neurotoxin 1 from Naja haje anchietae (Angolan cobra), Naja haje haje (Egyptian cobra), and Boulengerina annulata annulata (banded water cobra), respectively.

Keywords: Naja haje haje ; Venom; Mitochondrial membrane potential; Apoptosis; Cytochrome c; Histone deacetylases; Caspases; Cell cycle; Flow cytometry

Combined effect of fluoride and 2,3,7,8-tetrachlorodibenzo-p-dioxin on mouse dental hard tissue formation in vitro by Eija Salmela; Pirjo-Liisa Lukinmaa; Anna-Maija Partanen; Carin Sahlberg; Satu Alaluusua (pp. 953-963).

Fluoride interferes with enamel matrix secretion and mineralization and dentin mineralization. The most toxic dioxin congener, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), also impairs dental hard tissue formation and mineralization in vitro and in vivo. Our aim was to investigate in vitro whether the combined effect of sodium fluoride (NaF) and TCDD on dental hard tissue formation is potentiative. For this purpose, mandibular first and second molar tooth germs of E18 mouse embryos were cultured for 5–12 days with NaF and TCDD alone at various concentrations (2.5, 5, 10, 12.5, 15, and 20 μM and 5, 10, 12.5, and 15 nM, respectively) to determine the highest concentrations, which alone cause no or negligible effects. Morphological changes were studied from the whole tooth photographs and histological tissue sections. The concentrations found were 15 μM for NaF and 10 nM for TCDD. While at these concentrations, the effects of NaF and TCDD alone were barely detectable, the effect of simultaneous exposure on dentin and enamel formation was overt; mineralization of predentin to dentin and enamel matrix secretion and mineralization were impaired. Immunohistochemical analysis revealed that the combined exposure modified amelogenin expression by odontoblasts. Morphology of ameloblasts and the expression of amelogenin indicated that ameloblasts were still secretory. The results show that NaF and TCDD have potentiative, harmful effects on the formation of dental hard tissues. Since children can be exposed to subclinical levels of fluoride and dioxins during early childhood, coincidently with mineralization of the first permanent teeth, this finding may have clinical significance.

Keywords: Amelogenesis; Dentinogenesis; Fluoride; TCDD; Mouse

Porphyrogenic effect of pentabromodiphenyl ether after repeated administration to rats by Elżbieta Bruchajzer (pp. 965-974).

Until recently, pentabromodiphenyl ether (PentaBDE) was most commonly used as a flame retardant. On account of the hazardous effect of PentaBDE on the environment, its use was discontinued some years ago. The toxicity of this compound has been well documented in the literature, especially with regard to the endocrine system, induction of liver microsomal enzymes, and disturbance of redox homeostasis. The aim of this study was to investigate the porphyrogenic effect of PentaBDE after its repeated administration to rats at doses of 2, 8, 40, or 200 mg/kg/day. After a 28-day exposure, a dose-dependent increase (maximum 2.5-fold) in ALA-S activity in the liver was observed. The enhanced concentration of total porphyrins in the liver (3- to 19-fold after doses of 8–200 mg/kg/day) was also found. The most pronounced changes in liver concentrations of porphyrins were shown by high carboxylated porphyrins (a 19-fold increase for octacarboxyporphyrins and a 36-fold increase for heptacarboxyporphyrins). They made over 95% of total porphyrins accumulated in the liver. The porphyrogenic effect of PentaBDE was also evidenced by the augmented urinary excretion of total porphyrins. After 28 days of exposure, the observed changes (2- to 7-fold increase) were found to be dose-dependent. Tetracarboxyporphyrins predominated in urine; their urinary concentrations were 4–12 times higher, and their daily urinary excretion is 2–9 times higher. A dose of 2 mg/kg/day was the lowest dose that caused changes in the levels of porphyrins (LOAEL). The experiment revealed the effect of PentaBDE on the heme biosynthesis and porphyrin concentrations, which indicates its porphyrogenic effect.

Keywords: Pentabromodiphenyl ether (PentaBDE); Porphyrins; Repeated administration; Rat

Role of phospholipase D in regulation of testicular Leydig cell hyperplasia in Sprague–Dawley rats treated with di(2-ethylhexyl) phthalate by Young Jun Lee; Mee Young Ahn; Hyung Sik Kim; Seung Jun Kwack; Kul Lea Park; Sik Yoon; Dosik Min (pp. 975-985).

This study was conducted to determine the functional role of phospholipase D (PLD) involved in testicular Leydig cell damage caused by di (2-ethylhexyl) phthalate (DEHP) in Sprague–Dawley rats. DEHP (500 mg/kg/day) was administered orally to prepubertal rats for 1, 7, 14, 21 or 28 days. After 7 days of exposure, DEHP produced morphological changes in the testis, including alterations in seminiferous tubule diameters and loss of spermatogenic cells. Immunohistochemistry (IHC) analyses revealed that DEHP increased Leydig cell number in the testes as well as significantly increased the expression of PLD1/2 in Leydig cells after 7 days of exposure. Furthermore, the protein levels of phosphorylated extracellular signal-regulated kinase 1/2 (pERK1/2) increased in a similar manner to the PLD1/2 expression patterns. DEHP significantly reduced the expression of sperm-associated antigen 4 (Spag4) and lactate dehydrogenase A (LDHA) mRNA. In contrast, there was a significant increase in the expression of steroidogenic acute regulatory (StAR) mRNA against DEHP in a time-dependent manner, but serum testosterone concentration was decreased. These findings demonstrate that DEHP induces PLD expression in the testicular Leydig cells; this plays a key role in hyperplasia of Leydig cells and steroidogenic pathway via pERK1/2 activation.

Keywords: DEHP; Phospholipase D; Leydig cells; Hyperplasia; Steroidogenesis

Disruptive neuronal development by acrylamide in the hippocampal dentate hilus after developmental exposure in rats by Bunichiro Ogawa; Takumi Ohishi; Liyun Wang; Miwa Takahashi; Eriko Taniai; Hitomi Hayashi; Kunitoshi Mitsumori; Makoto Shibutani (pp. 987-994).

To examine whether developmental exposure to acrylamide (AA) impairs neuronal development, pregnant Sprague–Dawley rats were treated with AA at 0, 25, 50 or 100 ppm in drinking water from gestational day 6 until weaning on postnatal day 21. Offspring were immunohistochemically examined at the end of exposure. We investigated the expression of Reelin (a molecule regulating neuronal migration and positioning) in the hilus of the hippocampal dentate gyrus. As a positive control for direct exposure, AA (50 mg/kg body weight) was administered to pups by intraperitoneal injection 3 times per week during the lactation period. As well as pups directly injected with AA, maternally exposed offspring decreased body weight at 100 ppm; increased dose-dependently the number of Reelin-immunoreactive cells (from 25 ppm AA) and glutamic acid decarboxylase 67-immunoreactive cells (from 50 ppm AA), confirming an increase in γ-aminobutyric acid-ergic interneurons. We also noted decreased apoptosis in the neuroblast-producing subgranular zone of the dentate gyrus of maternally exposed pups at 100 ppm, as well as in directly AA-injected pups. These results suggest that a compensatory regulatory mechanism exists to correct impaired neurogenesis and mismigration caused by maternal exposure to AA during neuronal development. The lowest-observed-adverse-effect level of AA was determined to be 25 ppm (3.72 mg/kg body weight/day).

Keywords: Acrylamide; Developmental neurotoxicity; Neuronal migration; Neurogenesis; Dentate gyrus; GABAergic interneuron

An in vivo assessment of the genotoxic potential of bisphenol A and 4-tert-octylphenol in rats by Onur Kenan Ulutaş; Nurçin Yıldız; Emre Durmaz; Müfide Aydoğan Ahbab; Nurhayat Barlas; İsmet Çok (pp. 995-1001).

Bisphenol A (BPA) and octylphenol (OP) are industrial chemicals used in the manufacture of polycarbonate plastics, epoxy resins, and non-ionic surfactants. In the present study, we investigated the possible in vivo genotoxic effects of these compounds in rats using single-cell gel electrophoresis, the so-called comet assay. Adult male Wistar albino rats were divided randomly into six groups as follows: BPA125 (received 125 mg/kg bw BPA; n = 6), OP125 (received 125 mg/kg bw OP; n = 6), BPA250 (received 250 mg/kg BPA; n = 6), OP250 (received 250 mg/kg bw OP; n = 6), control (n = 5), and MMS (positive control group that received methyl methanesulfonate; n = 3). Both BPA and OP were orally administrated for 4 weeks. Controls were orally inoculated with corn oil for 4 weeks as well. Comet parameters including tail length and tail moment were evaluated for possible genotoxic effects. There were no significant differences in the OP125 and in the BPA125 compared with the control group, regarding tail length and tail moment (P > 0.05). However, there were significant differences in the OP250 and in the BPA250 compared with the control group, regarding tail length and tail moment (P < 0.05 and P < 0.01, respectively). The genotoxic potential of BPA and OP was investigated in vivo; there is a need for further studies exploring further mechanisms of the genotoxic potential of these chemicals in vivo.

Keywords: Bisphenol A; Octylphenol; Genotoxicity; Comet assay; Rat

Evaluation of in vivo genotoxic potential of fenofibrate in rats subjected to two-week repeated oral administration by Mohammad Monir Tawfeeq; Terumasa Suzuki; Keisuke Shimamoto; Hitomi Hayashi; Makoto Shibutani; Kunitoshi Mitsumori (pp. 1003-1011).

Fenofibrate (FF), a peroxisome proliferator-activated receptor-alpha agonist, has been used as one of the hypolipidemic drugs in man and induces oxidative stress and promotes hepatocarcinogenesis in the liver of rodents. This chemical belongs to a class of non-genotoxic carcinogens, but DNA damage secondary to oxidative stress resulting from reactive oxygen species (ROS) generation is suspected in rodents given this chemical. To examine whether FF has genotoxic potential, partially hepatectomized F344 male rats were treated orally with 0, 1,000 or 2,000 mg/kg of FF for 2 weeks, followed by diet containing 0.15% 2 acetyl aminofluorene (2 AAF) for enhancement the tumor-promoting effect for 10 days and a single oral dose of carbon tetrachloride (CCl4) as the first experiment (liver initiation assay). As the second experiment, the in vivo liver comet assay was performed in hepatectomized rats, and the expression of some DNA repair genes was examined. In the liver initiation assay, the number and area of glutathione S-transferase placental form (GST-P)-positive single cells and foci did not increase in the FF treated groups. In the comet assay, positive results were obtained after 3 h of the last treatment of FF, and the expression of some DNA repair genes such as Apex1, Ogg1 and Mlh1 were upregulated in rats given the high dose of FF at 3 h after the treatment but not in 24 h after the treatment. The results of the present study suggest that FF causes some DNA damage in livers of rats, but is not a strong genotoxic substance leading to a DNA mutation since such DNA damage was repaired by the increased activity of some DNA repair genes.

Keywords: Fenofibrate; Comet assay; Initiation assay; Genotoxicity; Rat

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Archives of Toxicology (v.85, #8)