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Abstract
The toxicity induced by insecticides in aquatic organisms is of utmost relevance because it may give a clue about the degree of health or damage of the involved ecosystem. In the present report, we determined the effect of dieldrin (DD) and chlorpyrifos (CP) on the freshwater crayfish, Cambarellus montezumae. The organisms (4-6 cm in diameter) were collected in the Ignacio Ramirez Reservoir, situated at 50 km Northeast of Mexico City, in the Rio Lerma Basin. Initially, we determined the LC50 value with the Probit method, then the DNA damage with single cell gel electrophoresis (comet assay applied at 24, 48, and 72 h of exposure) to the brain and hepatopancreas of animals exposed (in reconstituted water) to 0.05 and 0.5 microg/L of each insecticide. In the hepatopancreas of the same organisms, we determined the lipid peroxidation by applying the TBARS test. DNA damage and lipid peroxidation were also evaluated with the same methods to organisms exposed in water from the reservoir. In regard to the LC50, at 72 h of exposure, we found a value of 5.1 microg/L and a value of 5.62 microg/L for DD and CP, respectively. The comet assay applied at different exposure times showed significant DNA damage to both organs, with respect to the control level. In the case of DD, statistical significance was observed for the two doses in the whole evaluated schedule. CP was genotoxic in the brain with the high dose at 72 h, and in the hepatopancreas with the two tested doses at all evaluated exposure times. Also, a significant lipid peroxidation increase was detected with the two doses of insecticides. In the study with water from the reservoir, a more pronounced DNA damage was detected. Our results showed strong DNA damage induced by both insecticides in the crayfish, as well as a correlation with the lipid peroxidation effect, suggesting that oxidative stress is involved in the genotoxic alteration. Our results also showed the usefulness of the studied organism as well as the applied tests for the evaluation of toxicological effects, and suggested the pertinence of applying the comet assay to other freshwater organisms to evaluate the bioaccumulation of insecticides.
Highlights
Dieldrin (DD) is a cyclodiene insecticide originally formulated from a waste product of synthetic rubber
Chemicals and crayfishes: The following chemicals were obtained from SigmaAldrich Chemicals (St Louis, Mo, USA.): DD; CP; phosphate buffer saline (PBS); potassium chloride; tris; sodium carbonate; disodium ethylenediamine-tetra-acetate (EDTA); dimethyl sulfoxide (DMSO); reduced glutathione; hexane/isopropanol; thiobarbituric acid (TBA); trichloroacetic acid (TCA); Coomassie brilliant blue G; ethidium bromide (EB); bovine albumin; and butilated hydroxytoluene (BHT)
Data registered for the mortality induced by the insecticides in reconstituted water were examined with the Probit test
Summary
Dieldrin (DD) is a cyclodiene insecticide originally formulated from a waste product of synthetic rubber. The compound has been detected in a number of aquatic environments, suggesting that it may be involved in ecotoxicological damages (Palma, Palma, Fernandes, Soares, & Barbosa, 2008) Both insecticides have several common characteristics relevant to the aims of the present study: they are oxidative stress inducers, neurotoxicants in mammals and aquatic organisms, and are environmentally important contaminants because of their level of persistency (Martyniuk et al, 2010; Slotkin, & Seidler, 2010). It is highly recommended to apply various tests in order to determine the potentials of a particular chemical These tests are recommended when contradictory results are reported, as it stands in the present case, because it is well known that each test provides specific information on the type of DNA damage; a knowledge that is relevant to eventually implement antigenotoxic measures. Its application may contribute to define the genotoxic discrepancy reported on the insecticides, and if considered appropriate because of the present and new studies, it may be included in the field of ecotoxicology, as part of a battery for insecticides toxicological evaluation (Cotelle, & Férard, 1999)
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