S164 Abstracts / Toxicology Letters 211S (2012) S43–S216 Purpose: Vitamins with antioxidant properties have the ability to act as pro-oxidants, inducing oxidative damage opposed to pre- venting it. While vitamin supplements are popular, the scientific evidence for their health beneficial effects is inconclusive. In fact, even harmful effects have been reported. This study aimed to inves- tigate and compare pro-oxidant properties of different vitamins permitted in dietary supplements, alone or in combination with metals also found in supplements. Method: The vitamins’ ability to cause DNA related damages was investigated and compared. The DNA nucleoside deoxyguanosine (dG) or cultured cells (HL- 60) were exposed to vitamin. Oxidation of dG was analysed using high performance liquid chromatography, and damage to the DNA of HL-60 cells was analysed using the comet assay, as DNA strand breaks, alkali labile sites or oxidative DNA lesions, i.e. formamido pyrimidine DNA glycosylase-sensitive sites. Results and conclusion: Among 13 vitamins and antioxidants, vitamins A and C stood out, chemically inducing oxidation of dG, alone and in synergism with iron or copper. Two out of four (retinol, retinyl acetate) vitamin A compounds permitted in supplements induced oxidation to dG, and one (-carotene) induced a small increase in oxidative DNA lesions. Ascorbic acid, sodium ascorbate and calcium ascorbate, three out of four vitamin C compounds found in supplements, induced oxi- dation to dG. Overall, the combination of vitamin C (ascorbic acid) and Cu stood out inducing oxidation to both dG and DNA of cells, in a synergistic manner – a potential concern since both are found in supplements. doi:10.1016/j.toxlet.2012.03.594 P26-07 Studies of phytotoxicity of carbon-based nanoparticles on edible plants model Refi Ikhtiari, Parvin Begum, Bunshi Fugetsu Hokkaido University, Japan Graphene and carbon nanotubes (CNTs) are the most attractive carbon-based nanoparticles due to their outstanding properties. Their application increasingly used for medical application, in food production and agriculture, and to meet industrial demand. The negative effects of carbon based nanoparticles following envi- ronmental exposure have recently received significant attention. However, the data of phytotoxicity on edible plants model are just beginning to emerge. In our study, the toxic effect of Graphene and CNTs are commenced by preliminary screening using several plant species: cabbage, chili, cucumber, lady’s finger, lettuce, red spinach, rice, soybean and tomato. After 15 days in vivo hydroponic cultivation condition contain- ing Hoagland media supplemented with carbon nanoparticles at different concentrations (0, 125, 250, 500, 1000 and 2000 mg/L) the root, shoot growth and biomass were inhibited compared to control. Histochemical detection of reactive oxygen species (ROS) using 3-3 ′ -diaminobenzidine (DAB) and 2 ′ ,7 ′ -dichlorfluorescein- diacetate (DCFH-DA) assays that indicated an overproduction of ROS in the treated plants. Cell death in the leaves and roots pretreated with carbon nanoparticles was estimated by Evans blue staining. Light microscopy showed carbon nanoparticles are aggregated on the root surfaces which may not pass through the cell membrane (epidermis), confirmed by scanning electron microscopy (SEM). In advance, transmission electron microscope (TEM) images exhibit inner membrane damage, chromatin conden- sation and deformation within cell. We summarized that overproduction of ROS induced by car- bon nanoparticles could be responsible for significant plant growth inhibition and biomass reduction compared to control. The potential adverse effects of carbon nanoparticles deserve further attention. doi:10.1016/j.toxlet.2012.03.595 P26-08 Ochratoxin A induced oxidative stress in rat liver Saziye Sezin Palabiyik 1 , Pinar Erkekoglu 2 , N. Dilara Zeybek 2 , Murat Kizilgun 3 , Gonul Sahin 2 , Belma Giray 2 1 Hacettepe, Turkey, 2 Hacettepe University, Turkey, 3 Diskapi Children’s Hospital, Turkey This study was designed to examine the oxidative stress poten- tial of ochratoxin A (OTA) on rat liver. Male Spague-Dawley rats (200 g) were used in the experiments. Control group was fed with regular diet while OTA treated group was fed with reg- ular diet and received 0.5 g/kg bw dose OTA by gavage for 14 days. Histopathological examinations were performed and apopto- tis was assessed by TUNEL assay. Besides, biochemical parameters (plasma ALT and AST) and activities of antioxidant selenoenzymes [glutathione peroxidase 1 (GPx1), thioredoxin reductase (TrxR)], catalase (CAT), superoxide dismutase (SOD) and total glutathione (GSH) concentrations in liver tissues were measured. The focal necrosis of hepatocytes and mononuclear cell infiltration were observed in OTA treated group in the light microscopic observa- tion of liver tissues. Plasma AST levels showed a marked decrease of 71% (p < 0.05), while no changes were observed in plasma ALT levels. OTA treatment was found to induce oxidative stress in rat liver, as evidenced by significant decreases in GSH levels (∼40%). Furthermore, TUNEL analysis revealed a significant increase in the number of TUNEL-positive hepatocytes (∼170%) in OTA adminis- trated group compared to control (p < 0.05). The results of this study suggest that at least one of the mechanisms underlying the hepatic toxicity of OTA is oxidative stress. doi:10.1016/j.toxlet.2012.03.596 P26-09 Histopathological findings, oxidative stress and ultrasound measurements in heart tissues after long term rabbits exposure to chlorpyrifos Persefoni Fragkiadaki 1 , Ioannis Germanakis 2 , Alexandros Zafeiropoulos 3 , Aleka Kalogeraki 3 , Konstantinos Tsarouchas 3 , Christina Tsitsimpikou 4 , George Dolapsakis 3 , Aristidis Tsatsakis 3 , Demetrios Kouretas 5 1 University of Crete, Medical School, Greece, 2 General University Hospital of Heraklion, Greece, 3 University of Crete, Greece, 4 General Chemical State Laboratory, Greece, 5 University of Thessaly, Greece Purpose: Chlorpyrifos (CP) is one of the most widely used organophosphate insecticides. Although the mechanism of acute CPF toxicity involves acetylcholinesterase inhibition, other mech- anisms, including the induction of oxidative stress, have been implicated. In the present study, the possible deleterious effect of chlorpyrifos, on rabbit’s heart tissues was studied. Methods: Six healthy multicoloured female rabbits of indefinable variety (weight 3200–3500 g each) were administered of chlorpyrifos (17.54 mg/kg -1 /day) for 11 months. Three animals were used as controls. All rabbits before their extermination underwent a complete echocardiographic evaluation. For histological character-