Search

Simultaneous exposure of rat lymphocytes to 7 mT static magnetic field (SMF) and iron ions caused an increase in the number of cells with DNA damage. The mechanism by which MF induces DNA damage and the possible cytotoxic consequences are not known. However, we suppose that free radicals are involved. Potentially, the deterioration of DNA molecules by simultaneous exposure to 7 mT SMF and iron ions may lead to cell death: apoptosis or necrosis. The possible prooxidative properties of these two agents may result in an induction of the lipid peroxidation process as a marker of free radical mechanism in the cells. Experiments were performed on rat blood lymphocytes incubated for 3 h in Helmholtz coils at SMF of flux density 7 mT. During SMF exposure, some samples were treated with ferrous chloride (10 microg/ml), the rest serving as controls. We used the dye exclusion method with the DNA-fluorochromes: ethidium bromide and acridine orange. No significant differences were observed between unexposed lymphocytes incubated with medium alone and lymphocytes exposed to 7 mT SMF. Three-hour incubation with FeCl(2) (10 microg/ml) did not affect cell viability. However, when lymphocytes were exposed to 7 mT SMF and simultaneously treated with FeCl(2), there was a significant increase in the percentage of apoptotic and necrotic cells accompanied by significant alterations in cell viability. As compared to lipid peroxidation, there is a significant increase in the amount of lipid peroxidation end products MDA+4 HNE in rat lymphocytes after simultaneous exposure to 7 mT SMF and FeCl(2) (vs. to the control samples and those exposed to SMF alone). This suggests that 7 mT static magnetic field in the presence of Fe(2+) ions can increase the concentration of oxygen free radicals and thus may lead to cell death.

We have previously shown that simultaneous exposure of rat lymphocytes to iron ions and 50Hz magnetic field (MF) caused an increase in the number of cells with DNA strand breaks. Although the mechanism of MF-induced DNA damage is not known, we suppose that it involves free radicals. In the present study, to confirm our hypothesis, we have examined the effect of melatonin, an established free radicals scavenger, on DNA damage in rat peripheral blood lymphocytes exposed in vitro to iron ions and 50Hz MF. The alkaline comet assay was chosen for the assessment of DNA damage. During pre-incubation, part of the cell samples were supplemented with melatonin (0.5 or 1.0mM). The experiments were performed on the cell samples incubated for 3h in Helmholtz coils at 7mT 50Hz MF. During MF exposure, some samples were treated with ferrous chloride (FeCl2, 10microg/ml), while the rest served as controls. A significant increase in the number of cells with DNA damage was found only after simultaneous exposure of lymphocytes to FeCl2 and 7mT 50Hz MF, compared to the control samples or those incubated with FeCl2 alone. However, when the cells were treated with melatonin and then exposed to iron ions and 50Hz MF, the number of damaged cells was significantly reduced, and the effect depended on the concentration of melatonin. The reduction reached about 50% at 0.5mM and about 100% at 1.0mM. Our results indicate that melatonin provides protection against DNA damage in rat lymphocytes exposed in vitro to iron ions and 50Hz MF (7mT). Therefore, it can be suggested that free radicals may be involved in 50Hz magnetic field and iron ions-induced DNA damage in rat blood lymphocytes. The future experimental studies, in vitro and in vivo, should provide an answer to the question concerning the role of melatonin in the free radical processes in the power frequency magnetic field.

The three tetramethyl isomers of benzene (prenitene, 1,2,3,4-; izodurene, 1,2,3,5-; and durene, 1,2,4,5-tetramethylben- zene) were studied using in vitro mutagenicity and in vivo genotoxicity tests. Potency of mutate induction by these solvents was evaluated in Salmonella typhimurium cells with, and without S9-mix made from Aroclor 1254-induced rat liver S9. The potency of induction of micronuclei (MN) and sister chromatid exchanges (SCEs) by solvents was evaluated in bone marrow of mice. Izodurene displayed mutagenic potency in strains TA97a, TA98 and TA100 only in the absence of the S9-mix. In MN tests, all three tetramethylbenzenes demonstrated no clastogenic activity on the bone marrow cells. All the tested solvents were active as genotoxic compounds in the SCE tests, demonstrating a dose-response relationships., (Copyright 1999 Elsevier Science B.V.)

A combination of assays for gene mutations in Salmonella typhimurium TA97a, TA98, TA100 and TA102 strains with and without rat liver activation, and for micronucleus and sister chromatid exchange (SCE) in bone marrow cells of Imp:Balb/c mice was used to provide data on the mutagenic and genotoxic properties of the mixture of aromatic solvents, known under the trade name of Farbasol. In addition, 4-ethyltoluene (the main ethylmethylbenzenic component of Farbasol) was also tested for muta- and genotoxicity. The results revealed that neither Farbasol nor 4-ethyltoluene induced an increased reverse mutation in bacterial cells or the formation of micronucleated polychromatic erythrocytes in bone marrow. However, those compounds were found to be active as sister chromatid exchange (SCE) agents., (Copyright 1998 Elsevier Science B.V.)

The three trimethyl isomers of benzene (hemimellitene, 1,2,3-TMB; pseudocumene, 1,2,4-TMB and mesitylene, 1,3,5-TMB) were investigated for different genotoxicity endpoints: in vitro, in the Ames test with Salmonella typhimurium TA97a, TA98, TA100 and TA102 strains in the presence and absence of rat liver S9 metabolic activation; in vivo, in the micronucleus and sister chromatid exchange (SCE) tests with bone marrow cells of Imp:Balb/c mice. Only the isomer of benzene with the methyl-group at position 1, 2, 3 was found to have mutagenic effect on S. typhimurium cells. Increase in bacterial reversions was observed in four conventional strains used in this study, but most clearly in TA97a. The mutagenic responses of 1,2,3-TMB with the SalmonellaL tester strains were observed in the experiments performed in the absence of enzymatic activation. None of the compounds had an influence on the frequency of micronucleated polychromatic erythrocytes in bone marrow cells of mice. However, all the three compounds were observed to have a cytogenetic potential of increasing the SCE level in these cells. Significant responses in SCE induction, compared with the level of those changes in corresponding solvent-administered controls, were obtained at three test doses of 1,2,3-TMB (730, 1470, 2200 mg/kg) and 1,2,4-TMB (900, 1800, 2700 mg/kg) and at two doses of 1,3,5-TMB (1800, 2700 mg/kg). These data provided a limited evidence for the genotoxic activity of 1,2,3-TMB and inadequate evidence for genotoxic activity of 1,2,4-TMB and 1,3,5-TMB.

The genotoxic effects of triarylmethane (Acid Green 16, C.I.44025) and arylmonoazo (Basic Orange 28, developed by Boruta Pigment Plant, Poland, C.I. undisclosed) dyes, were evaluated in Balb/C mice. Animals were fed for 6 days nutritionally adequate Portagen liquid diet (1 kcal/ml) or isocaloric alcoholic diet containing 5% (w/v) ethanol (36% of total calories) in order to induce the cytochrome P-4502E1 monooxygenase. Dye compounds were administered intraperitoneally 30 h before the test at doses: 90 mg/kg of Acid Green 16 and 70 mg/kg of Basic Orange 28. Bone marrow micronucleus test was used for evaluation of genotoxicity of the dyes. Ethanol caused an increase of the level of cytochrome P-450 by 200% and activities of 7-ethoxycoumarin O-deethylase (ECOD) by 650%, 7-ethoxyresorufin O-deethylase (EROD) by 460% and glutathione (GSH)-S-transferase by 60% in the liver. Both dyes exerted genotoxic effect as inferred from a 3-fold increase of frequency of micronucleated polychromatic erythrocytes in bone marrow, and a further increase (2-fold) was caused by ethanol liquid diet combined with Acid Green 16 treatment. Basic Orange 28 genotoxicity remained unaffected by ethanol. It is concluded that: (1) enhancement of genotoxic effect of Acid Green 16 by ethanol is caused by induction of cytochrome P-4502E1 monooxygenases resulting in an increased bioactivation of the dye; (2) lack of enhancement of the genotoxic effect of Basic Orange 28 by ethanol probably results from the dye- and ethanol-mediated stimulation of GSH-S-transferase, bypassing the cytochrome P-4502E1 bioactivation step.