G. Ribas

Herbicide-induced DNA damage in human lymphocytes evaluated by the single-cell gel electrophoresis (SCGE) assay.

The genotoxicity of the herbicides, alachlor, atrazine, maleic hydrazide, paraquat and trifluralin has been evaluated in the single-cell gel electrophoresis (SCGE) assay by using human peripheral blood lymphocytes. All treatments were conducted with and without the presence of an external bioactivation source (S9 mix). The results indicate that all the herbicides tested are able to give positive results by increasing the comet tail length, which would confirm both the genotoxicity of the herbicides and the sensitivity of the assay in front of these chemicals. Alachlor and atrazine give similar results in treatments with and without S9, while when the S9 mix was not used paraquat and trifluralin genotoxicity was higher. On the other hand, although maleic hydrazide genotoxicity was higher when S9 mix was used at normal pH (7.4), our data show that its genotoxicity depends largely on the pH solution, increasing as the pH decreased.

Genotoxicity of four herbicides in the Drosophila wing spot test

The herbicides alachlor, atrazine, maleic hydrazide and paraquat were evaluated for genotoxicity in the Drosophila melanogaster wing spot test. Third-instar larvae trans-heterozygous for two recessive mutations of wing trichomes, multiple wing hairs (mwh) and flare (flr3), were treated by chronic feeding with different concentrations of the four herbicides. Feeding ended with pupation of the surviving larvae. The genotoxic effects were determined from the appearance of clones of cells with mwh, flr3 or mwh-flr3 phenotypes. Exposure to maleic hydrazide resulted in a significant increase in the frequency of the three categories of spots recorded (small single, large single and twin spots) in a dose-related fashion. Exposure to alachlor induced significant increases in both small and total spots at the four concentrations assayed and in the frequency of twin spots at the highest concentration tested (10 mM). Atrazine and paraquat also induced significant increases in both small and total spots at three of the four concentrations tested, without indication of a direct dose-effect relationship.

Lack of genotoxicity of the herbicide atrazine in cultured human lymphocytes

The widely used herbicide atrazine was evaluated for genotoxicity in cultured human peripheral blood lymphocytes. Sister-chromatid exchanges (SCE), chromosome aberrations (CA) and micronuclei (MN) were scored as genetic endpoints. To detect eventual metabolic modification in the genotoxicity of this herbicide, the cultures of SCE and MN demonstration were also treated with S9 microsomal fraction. From our results we can conclude that atrazine was able to exert a weak cytotoxic effect. However, the overall evaluation of the genotoxicity data indicate that this herbicide is not effective in the three assays conducted, irrespective of the presence of metabolic activation, which would mean a general lack of effectiveness of atrazine to induce clastogenic and aneugenic damage in cultured human lymphocytes.

Genotoxic evaluation of the herbicide paraquat in cultured human lymphocytes.

The widely used herbicide paraquat was evaluated for genotoxicity in peripheral blood human lymphocyte cultures. Sister-chromatid exchanges (SCE), chromosome aberrations (CA), and micronuclei (MN) were scored as genetic endpoints. Paraquat was administered either alone or in combination with an external source of metabolic activation. Our data indicate that paraquat induced slight but significant increases in the frequency of SCE. This genotoxic effect was not modified by cotreatments with S9 fraction from rat liver. However, paraquat did not increase the frequency of CA and MN, indicating that this bipyridylium compound is not effective in these assays, which would mean a general lack of effectiveness of the herbicide to induce clastogenic damage. In addition, cotreatments with the S9 fraction, did not modify the genotoxic ability detected in the SCE assay.

Genotoxic evaluation of the herbicide trifluralin on human lymphocytes exposed in vitro.

The herbicide trifluralin was evaluated for genotoxicity in cultured human peripheral blood lymphocytes. Sister-chromatid exchanges (SCE), chromosome aberrations (CA) and micronuclei (MN) were scored as genetic endpoints. To detect eventual metabolic modification in the genotoxicity of this herbicide, the cultures for SCE and MN demonstration were also treated with S9 fraction. From our results we can conclude that trifluralin was able to exert a weak cytotoxic effect, reducing both the proliferative rate index (PRI) and the cytokinesis block proliferation index (CBPI), and also to induce a slight but statistically significant increase in the frequency of SCE. Under our conditions of testing, no genotoxic effects of trifluralin were observed in the CA and MN assays.

Sister-chromatid exchanges (SCE) induction by inhibitors of DNA topoisomerases in cultured human lymphocytes.

The induction of sister-chromatid exchanges (SCE) in cultured human lymphocytes by four inhibitors of DNA topoisomerases: m-amsacrine, camptothecin, etoposide and nalidixic acid has been evaluated. Although the four compounds apparently increase the frequency of SCE, the effect of nalidixic acid is weak because only a statistically significant positive response was found in one donor at the highest concentration (500 microM). The other compounds tested act as SCE inducers in both donors, camptothecin being the most effective. In addition, the influence of these four topoisomerase inhibitors on the SCE frequency induced by MMC was also analysed. The results reveal that less than additive SCE effect was induced by the combined treatments which could suggest that the process leading to SCE induction by MMC and the four inhibitors of DNA topoisomerases are not totally independent.

Genotoxicity of humic acid in cultured human lymphocytes and its interaction with the herbicides alachlor and maleic hydrazide

The genotoxicity of humic acid and its possible interaction with the herbicides alachlor and maleic hydrazide have been evaluated in cultured human lymphocytes from two donors. Humic acid and the two herbicides have been tested (alone and combined) for sister‐chromatid exchange (SCE) induction. In addition, the effect of two different preincubation times, 2 and 24 hr, was analyzed. The results indicate that humic acid and the herbicides alachlor and maleic hydrazide appear to signifi‐cantly enhance the frequency of SCE, the effect of the herbicides being more pronounced. With reference to the possible interaction of humic acid with the herbicides, the results do not show a common pattern, although mainly an additive effect was obtained. Nevertheless, there is some evidence suggesting that antagonism may occur, especially in the combined treatment of humic acid and maleic hydrazide. Environ. Mol. Mutagen. 29:272‐276, 1997

Germinal and somatic mutation induction in Drosophila after treatment of larvae with tritiated water

The present study was carried out to evaluate the mutagenicity of tritium, administered as tritiated water, in Drosophila melanogaster. Larvae were fed on tritium-treated medium during their development. Germinal and somatic mutation induction was detected by means of the sex-linked recessive lethal and the wing spot tests, respectively. Our results show that beta-radiation from tritium is able to induce significant increases in the frequency of both germinal and somatic mutations.

Genotoxicity of tritiated water in human lymphocytes

The present study was carried out to evaluate the genotoxicity of tritium, administered as tritiated water, in peripheral blood human lymphocyte cultures. Sister-chromatid exchanges (SCE) and chromosome aberrations (CA) were scored as genetic endpoints. From our results we can conclude that beta-radiation from low concentrations of tritium was able to induce a significant increase in the frequency of CA, although it was ineffective in increasing the frequency of SCE.