Combined effects of deltamethrin, temperature and salinity on oxidative stress biomarkers and acetylcholinesterase activity in the black tiger shrimp (Penaeus monodon)

This study aimed to investigate the interactions of two abiotic factors (temperature and salinity) and deltamethrin (pyrethroid pesticide) exposure on some oxidative stress biomarkers as well as on acetylcholinesterase activity (AChE) in hepatopancreas, gills and muscle of black tiger shrimp (Penaeus monodon). A combination of three temperatures (24, 29 and 34 °C), two salinities (15 and 25 ppt), and the absence or presence of 0.1 μg L⁻¹ deltamethrin was applied on shrimp during 4 d under laboratory conditions. Lipid peroxidation level (LPO) and glutathione S-transferase activity (GST) were not affected by combined effect of temperature, salinity and deltamethrin in any of the studied tissues. Deltamethrin impaired other tested oxidative stress biomarkers, i.e. total glutathione (tGSH), catalase (CAT), glutathione peroxidase (GPx). tGSH level significantly increased in hepatopancreas due to deltamethrin exposure mainly at 34 °C, while pesticide effects on tGSH and CAT activity in gills were influenced by both temperature and salinity. In addition, GPx activity in hepatopancreas decreased after deltamethrin treatment mainly at 24 °C. Finally, AChE in muscle was strongly inhibited by deltamethrin at all tested temperatures and salinities. These novel findings demonstrate that interactions between abiotic factors and a commonly used pesticide exposure should be taken into account when analyzing some widespread biomarkers in black tiger shrimp.     

Endocrine response of the freshwater teleost, Sarotherodon mossambicus (Peters) to dimecron exposure

The endocrine response in a freshwater teleost, Sarotherodon mossambicus (Peters) under dimecron (an organophosphate pesticide) toxicity was investigated by estimating the serum levels of T3 (triiodothyronine), T4 (thyroxine), cortisol, prolactin and insulin in control and sub-lethal (0.001 ml l(-1)) dimecron-exposed fish for 1, 6, 12, 24h and 5 days. In control S. mossambicus, the serum levels of T3 ranged from 0.80+/-0.01 to 0.82+/-0.01 ng ml(-1); T4 from 2.20+/-0.01 to 2.25+/-0.01 microg dl(-1); cortisol from 8.30+/-0.03 to 8.34+/-0.01 microg dl(-1); prolactin from 1.50+/-0.01 to 1.54+/-0.01 microg ml(-1); insulin from 9.70+/-0.01 to 9.76+/-0.01 microU ml(-1) up to a maximum period of 5 days maintained in pollutant-free tap water. Exposure of fish to sub-lethal concentration of dimecron caused varying changes in the levels of serum hormones studied. Based on the results obtained, it was concluded that (i) the fish adaptively maintains a probable low metabolic rate, as indicated by the reduced levels of thyroid hormone (T3) as well as the glucocorticoid hormone (cortisol), which could be considered advantageous for the fish to indirectly reduce the toxic impact of the pesticide, (ii) the elevated levels of prolactin in the fish under pesticide stress is indicative of a possible hydromineral regulatory effect of the hormone (probably by influencing specific organs such as gills and kidney) under pesticide toxicity, (iii) the increased insulin level in the fish under pesticide stress is indicative of its role in favouring an adaptive tissue glycogenesis besides a possible increased lipogenesis to sequester the pesticide residue thereby reducing the toxic effect of the pesticide and (iv) the prolonged exposure of the fish (for 5 days) to sub-lethal dimecron appeared to exhibit a uniform recovery response in the different hormonal levels of the fish.     

Ascorbic acid supplementation of diet for reduction of deltamethrin induced stress in freshwater catfish Clarias gariepinus

Static bioassays were made to evaluate efficiency of supplementation of ascorbic acid to remove stress of pyrethroid pesticide deltamethrin from freshwater catfish Clarias gariepinus. Clarias gariepinus exhibited several symptoms of stress when treated with deltamethrin (0.005 mg/l) for 24 h. Hepatosomatic index, liver glycogen, ascorbic acid of blood, liver, and kidney decreased while plasma glucose levels increased. Fish previously fed for 60 days with a diet supplemented by a high level of ascorbic acid (100 mg/100 g) could remove most of the stresses. Low levels of ascorbic acid supplement did not remove the stress. Dietary supplement of ascorbic acid at also appropriate level appeared to be a good way to counter toxicity of deltamethrin to the catfish.     

Distribution of nickel in the roach (Rutilus rutilus L.) after exposure to lethal and sublethal concentrations

In order to evaluate the eventual impact of nickel in fish kills occuring in the river Meuse in Belgium, a series of experiments were performed in which the uptake and distribution of nickel in Rutilus rutilus L., one of the dominant species in the river was studied after administration of nickel alone and in combination with other metals. In decreasing order the highest nickel concentrations were found in gill, opercle, kidney, liver and muscle. After exposure to nickel in combination with copper or chromium nickel levels in gill tissue increased significantly compared to levels encountered when fish were exposed to the same concentration of nickel alone. When the pH of the test solution was lowered from 8.0 to 6.5, the lethal action and the accumulation of nickel in gill tissue increased. Control fish collected from a surface water storage reservoir and from the river Meuse had higher nickel levels in the opercle than in gill tissue.     

Deltamethrin residues in milk and tissues of lactating dairy cows.

Lactating dairy cows were fed deltamethrin (2 or 10 mg kg-1 feed) for 28 consecutive days and deltamethrin residues measured in milk and tissues. Deltamethrin residues were higher relative to dose administered. The order of relative concentrations of deltamethrin in tissues, measured 1, 4, and 9 days after the last dose was: renal fat greater than subcutaneous fat greater than forequarter muscle greater than hindquarter muscle greater than liver greater than kidney. Depletion of deltamethrin residues in milk was very rapid indicating the half-life of the insectide of about 1 day. Trace amounts of deltamethrin metabolites 3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane carboxylic acid (less than 0.0235 ppm) and 3-phenoxybenzoic acid (less than 0.034 ppm) were also detected in milk and tissues of treated cows.     

Seasonal variations in cholinesterase activity, nerve conduction velocity and lung function among sprayers exposed to mixture of pesticides

Pesticide spraying operation is associated with the increased risk of adverse health effects among sprayers who do not follow safe farm work practices. A study was conducted among pesticide sprayers in North India to evaluate the clinical and subclinical variations in their vital health parameters before and after the pesticide spraying season. Blood cholinesterase levels, pulmonary function test, nerve conduction velocity and self-reported symptoms were studied among 18 eligible and consenting male sprayers. Mean acetylcholinesterase activity was reduced by 55 % in the post-exposure assessment (P?<?0.001) as compared to pre-exposure levels. Mean forced expiratory volume in 1 s was 20 % lower in the post-exposure assessment as compared to the pre-exposure level (P?<?0.05). No significant change was observed in the motor and sensory nerve conduction velocity in the median nerve of sprayers before and after the spraying activity. Also, no significant variation was observed with respect to self-reported symptoms except weakness in arms and legs (P?<?0.05). The significant decline in lung function and acetylcholinesterase level after pesticide exposure reflects the strongly negative effect of exposure to pesticides during spraying activity. More longitudinal studies among pesticide sprayers must be undertaken to further substantiate the cause–effect relationship between pesticide exposure and its subclinical effects. There is a strong necessity to minimise the exposure through the use of personal protective equipment in pesticide sprayers.     

Pesticides and essential minerals modify endogenous antioxidants and cytochrome P450 in tissues of rats

Two experiments were conducted in male Sprague Dawley (SD) rats (175-200 g) to determine changes in the activities of endogenous antioxidants superoxide dismutase (SOD), glutathione peroxidase (GPX), cytochrome P450 (ethoxyresorufin deethylase; EROD) and concentrations of glutathione (GSH) in the blood, liver, and small intestinal mucosa (IM). In both experiments, six rats/group were fed diets based on the AIN-93M diet (Control) or the same modified to contain either 500 mg calcium (Low Ca), 7 mg Zn (Low Zn): 2 mg copper (Low Cu), 60 mg zinc (High Zn) or 12 mg copper (High Cu) in the following combination: Control, LCa/LZn, LCa/LZn/LCu, or HZn/HCu, with and without a pesticide mixture containing acephate, endosulfan, and thiram at 25% LD50 for four or two weeks. Pesticides decreased feed intake and weight gain in all groups by 28%. Erythrocyte SOD was higher than control in the HZn/HCu group and in the LCa/LZn/LCu and HZn/HCu groups with pesticide (P#0.05). Plasma GPX declined by more than 55% in all the groups with and without pesticides compared to the control. The LCa/LZn/LCu and HZn/HCu diets with and without pesticides reduced GPX in the IM by up to 88%, 40%, and 74%, respectively, than the control. Plasma GSH was about 20% higher than the control in most groups with and without pesticides in the diet. Liver and IM GSH were higher than the control in the HZn/HCu group, whereas IM GSH concentrations were lower than the control in the LCa/LZn and LCa/LZn/LCu groups (P#0.05). All three experimental diets with and without pesticides had a significant effect on liver EROD activity (P#0.05). The results indicate that endogenous antioxidants and EROD were independently modified by dietary zinc and copper levels and pesticides.     

Pesticides and Essential Minerals Modify Endogenous Antioxidants and Cytochrome P450 in Tissues of Rats

Two experiments were conducted in male Sprague Dawley (SD) rats (175–200 g) to determine changes in the activities of endogenous antioxidants superoxide dismutase (SOD), glutathione peroxidase (GPX), cytochrome P450 (ethoxyresorufin deethylase; EROD) and concentrations of glutathione (GSH) in the blood, liver, and small intestinal mucosa (IM). In both experiments, six rats/group were fed diets based on the AIN-93M diet (Control) or the same modified to contain either 500 mg calcium (Low Ca), 7 mg Zn (Low Zn): 2 mg copper (Low Cu), 60 mg zinc (High Zn) or 12 mg copper (High Cu) in the following combination: Control, LCa/LZn, LCa/LZn/LCu, or HZn/HCu, with and without a pesticide mixture containing acephate, endosulfan, and thiram at 25% LD₅₀ for four or two weeks. Pesticides decreased feed intake and weight gain in all groups by 28%. Erythrocyte SOD was higher than control in the HZn/HCu group and in the LCa/LZn/LCu and HZn/HCu groups with pesticide (P# 0.05). Plasma GPX declined by more than 55% in all the groups with and without pesticides compared to the control. The LCa/LZn/LCu and HZn/HCu diets with and without pesticides reduced GPX in the IM by up to 88%, 40%, and 74%, respectively, than the control. Plasma GSH was about 20% higher than the control in most groups with and without pesticides in the diet. Liver and IM GSH were higher than the control in the HZn/HCu group, whereas IM GSH concentrations were lower than the control in the LCa/LZn and LCa/LZn/LCu groups (P#0.05). All three experimental diets with and without pesticides had a significant effect on liver EROD activity (P#0.05). The results indicate that endogenous antioxidants and EROD were independently modified by dietary zinc and copper levels and pesticides.     

Toxic effects of deltamethrin and λ-cyhalothrin on Xenopus laevis tadpoles

This study evaluates the toxic effects of deltamethrin and λ-cyhalothrin on Xenopus laevis tadpoles after 168 h of exposure. The LC(50) of deltamethrin and λ-cyhalothrin at 168 h was calculated as the μg of active ingredient per liter (μg AI/L). According to these values, the LC(50) was 6.26 and 3.94 μg AI/L for deltamethrin and λ-cyhalothrin, respectively. Several enzymes were studied for early signs of intoxication following exposure to the pesticides for 24 h. Glutathione-S-transferase,carboxylesterase, and lactate dehydrogenase were inhibited by λ-cyhalothrin, and both pesticides inhibited acid phosphatase and aspartate aminotransferase. In contrast, acetylcholinesterase was activated by deltamethrin. The results suggest that X. laevis is sensitive to the pyrethroids that were tested, and the enzyme responses suggest that they are potential biomarkers for evaluating the toxic effect of pyrethroids on amphibians in environmental conditions.     

Exposure to sublethal concentrations of Zn(II) and Cu(II) changes biochemical parameters in Leporinus obtusidens

The aim of the present study was to assess the effect of the exposure of Leporinus obtusidens (Piava) to zinc and copper on catalase activity in the liver, delta-aminolevulinate dehidratase (delta-ALA-D) activity in liver, muscle, brain and kidney, and thiobarbituric reactive species (TBARS) in brain, muscle and liver. In addition, hematological parameters were measured in blood. The fish were exposed to 10% and 20% of the derived LC(50) values, 2.3 and 4.6 mg Zn l(-1) and 0.02 and 0.04 mg Cu l(-1), and sampled on days 30 and 45. Exposure to Zn(II) and Cu(II) decreased hematological parameters and also delta-ALA-D activity mainly in liver and kidney at all concentrations tested. Liver catalase activity increased after zinc or copper exposure at all concentrations and exposure times tested. Thiobarbituric reactive substances (TBARS) increased in the brain and liver of the fish exposed to zinc(II) for 45 days at both metal concentrations. In muscle, zinc(II) increased TBARS production at both exposure times and concentrations tested. Copper(II) exposure reduced the TBARS levels in liver at both concentrations and times tested. In brain, there was a decrease in TBARS levels only after 45 days of exposure. In muscle, this decrease was observed after 30 days of exposure at both concentrations. Although zinc and copper are required as microelements in the cells, our results showed that the sublethal concentrations of these metals can change biochemical parameters which may alter normal cellular function. These results pointed out the differential sensitivity of fish tissues to essential, but also toxic and environmentally relevant metals. The alterations of distinct biochemical parameters in fish tissues certainly contribute to the toxicity of Zn and Cu, and are of importance for an area that has been growing and has still been poorly explored in the literature.     

Effect of pesticide residues on health and different enzyme levels in the blood of farm workers from Gadap (rural area) Karachi-Pakistan

Persons from 14 different fruit and vegetable farm stations from Gadap (rural area), Karachi-Pakistan were examined for the presence of pesticide (cypermethrin, deltamethrin, polytrin-C, diazinon, monocrotophos, DDT and DDE) residues in their blood samples. The present study is concerned with effects of residue on the enzyme levels (GPT, GOT and ALP) as well as the health hazards of pesticide exposed persons. There is a significant increased in the enzyme levels at different stations. Exposed persons complained about liver and kidney dysfunctions and RTI. It may be concluded that exposure of multiple pesticides for prolonged period has affected the normal functioning of different organ systems and possibly produced characteristics clinical effects such as hepatitis, dyspnea and burning sensation in urine.     

Analysis of copper,zinc, cadmium and chromium in fish tissues. A tool for detecting metal caused fish kills

In order to find the causative agent in frequently occuring fish kills in a Belgian river a series of toxicity tests has been conducted in which rudd (Scardinius erythrophtalmus) were exposed to acute lethal and subacute non lethal concentrations of copper, chromium, cadmium and zinc. The concentrations of these metals in gills, opercle, kidney, liver and muscle were measured. Metal levels in gills were the most valuable indicator of acute lethal exposure. This information was compared with levels found in rudd from a surface water storage reservoir and from the river Meuse. Fish collected after fish kills in the river Meuse were analysed. In one case copper could be identified as one of the toxicants concerned by fish tissue analysis. Metal levels in fish tissues can give valuable additional information concerning the cause of kills provided that background information is available about metal levels in water and normal tissue levels.     

Multiple biomarkers responses in Prochilodus lineatus allowed assessing changes in the water quality of Salado River basin (Santa Fe, Argentina)

This field study assessed water quality of Salado River basin by using a set of biomarkers in the fish Prochilodus lineatus. Multiple biomarkers were measured, including morphological indexes (condition factor, liver somatic index), hematological (red and white blood cells) and biochemical (glucose, total protein and cholinesterase activity) parameters. Besides, detoxication and oxidative stress markers (antioxidant enzymes, lipid peroxidation) were measured in liver, gills and kidney. Despite water quality assessment did not show marked differences among sites, biomarkers responses indicate that fish are living under stressful environmental conditions. According to multivariate analysis glucose, glutathione S-transferase activity, lipid peroxidation levels and the count of white blood cells are key biomarkers to contribute to discrimination of sites. So, we suggest use those biomarkers in future monitoring of freshwater aquatic systems.     

Effects of thiol antioxidants on the atropselective oxidation of 2,2′,3,3′,6,6′-hexachlorobiphenyl (PCB 136) by rat liver microsomes

Chiral polychlorinated biphenyl (PCB) congeners, such as PCB 136, are atropselectively metabolized to various hydroxylated PCB metabolites (HO-PCBs). The present study investigates the effect of two thiol antioxidants, glutathione and N-acetyl-cysteine (NAC), on profiles and chiral signatures of PCB 136 and its HO-PCB metabolites in rat liver microsomal incubations. Liver microsomes prepared from rats pretreated with phenobarbital were incubated with PCB 136 (5 μM) in the presence of the respective antioxidant (0–10 mM), and levels and chiral signatures of PCB 136 and its HO-PCB metabolites were determined. Three metabolites, 5-136 (2,2′,3,3′,6,6′-hexachlorobiphenyl-5-ol), 4-136 (2,2′,3,3′,6,6′-hexachlorobiphenyl-4-ol), and 4,5-136 (2,2′,3,3′,6,6′-hexachlorobiphenyl-4,5-diol), were detected in all incubations, with 5-136 being the major metabolite. Compared to microsomal incubations without antioxidant, levels of 4,5-136 increased with increasing antioxidant concentration, whereas levels of PCB 136 and both mono-HO-PCBs were not affected by the presence of either antioxidant. PCB 136, 4-136, and 5-136 displayed significant atropisomeric enrichment; however, the direction and extent of the atropisomeric enrichment was not altered in the presence of an antioxidant. Because 4,5-136 can either be conjugated to a sulfate or glucuronide metabolite that is readily excreted or further oxidized a potentially toxic PCB 136 quinone, the effect of both thiol antioxidants on 4,5-136 formation suggests that disruptions of glutathione homeostasis may alter the balance between both metabolic pathways and, thus, PCB 136 toxicity in vivo.     

Acute toxicity of the insect larvicide abate® (temephos) on the fish tilapia melanopleura and the dragonfly larvae neurocordelia virginiensis.

Abstract

Acute bioassay tests on the toxic effects of the insect larvicide Abate® (temephos) on the mouth brooder cichlid fish Tilapia melanopleum and the dragonfly larvae (Odonata) Neurocordulia virginiensis were conducted in static non renewal toxicity test set ups. The 96h‐LC50 (95% confidence intervals) was 30.2 (20.5‐ 44.20) mg/L for the fish and 2.0 (1.16–2.0) mg/L for the dragonfly larvae. The dragonfly larvae were 15 times more susceptible to the larvicide than the tilapia. The calculated NOEC (No Observable Effect Concentration) was 14.1 mg/L for the fishand less than 1.0 mg/L for the insect larvae. The estimated ‘safe’ concentration of the pesticide to the fish was 3.0 mg/L and 0.2 mg/L for insect larvae. These figures are far above the concentrations approved for use in the control of mosquito larvae(0.0004–0.01 mg/L). It appears that the application of toxic levels of the insecticide for the elimination of some aquatic invertebrates may be ‘safe’ for normal survival, growth and reproduction offish and some aquatic insect larvae.     

The antioxidative response system in Glycine max (L.) Merr. exposed to Deltamethrin, a synthetic pyrethroid insecticide

Forty-five-day-old plants of Glycine max (soybean) were exposed to several Deltamethrin (synthetic pyrethroid insecticide) concentrations (0.00%, 0.05%, 0.10%, 0.15% and 0.20%) through foliar spray in the field conditions. In the treated plants, as observed at the pre-flowering (10 DAT), flowering (45 DAT) and post-flowering (70 DAT) stages, lipid peroxidation, proline content and total glutathione content increased, whereas the total ascorbate content decreased, as compared with the control. Among the enzymatic antioxidants, activity of superoxide dismutase, ascorbate peroxidase and glutathione reductase increased significantly whereas that of catalase declined markedly in relation to increasing concentration of Deltamethrin applied. The changes observed were dose-dependent, showing a strong correlation with the degree of treatment.     

Toxic effects of deltamethrin and λ-cyhalothrin on Xenopus laevis tadpoles

This study evaluates the toxic effects of deltamethrin and λ-cyhalothrin on Xenopus laevis tadpoles after 168 h of exposure. The LC₅₀ of deltamethrin and λ-cyhalothrin at 168 h was calculated as the μg of active ingredient per liter (μg AI/L). According to these values, the LC₅₀ was 6.26 and 3.94 μg AI/L for deltamethrin and λ-cyhalothrin, respectively. Several enzymes were studied for early signs of intoxication following exposure to the pesticides for 24 h. Glutathione-S-transferase,carboxylesterase, and lactate dehydrogenase were inhibited by λ-cyhalothrin, and both pesticides inhibited acid phosphatase and aspartate aminotransferase. In contrast, acetylcholinesterase was activated by deltamethrin. The results suggest that X. laevis is sensitive to the pyrethroids that were tested, and the enzyme responses suggest that they are potential biomarkers for evaluating the toxic effect of pyrethroids on amphibians in environmental conditions.     

Insecticides biomarker responses on a freshwater fish Corydoras paleatus (Pisces: Callichthyidae)

This study was undertaken to investigate the effects of sublethal concentration of three different classes of insecticides (carbamate, organophosphate, and pyrethroid compounds) on the freshwater fish Corydoras paleatus. For this purpose, fish were exposed for 96 hours to commercial pesticides. Different biomarkers were analyzed as levels of lipid peroxidation (LPO), piscine micronucleus test, and enzymatic activities of catalase (CAT), glutathione S-transferase (GST), and acetylcholinesterase (AChE). The brain AChE was inhibited with carbaryl and methyl parathion, but no inhibition was observed with deltamethrin. The insecticides did not cause oxidative stress or genotoxic effects at the tested concentrations. Further studies are needed to elucidate the biotransformation of Corydoras paleatus insecticides and a possible resistance mechanism.     

Comparing the response of biochemical indicators (biomarkers) and biological indices to diagnose the ecological impact of an oil spillage in a Mediterranean river (NE Catalunya, Spain)

Three biomarkers of hydrocarbon exposure, liver 7-ethoxyresourfin-O-deethylase activity (EROD), fluorescent hydrocarbon compounds (FACs) in bilis, and the liver antioxidant enzyme catalase (CAT) were examined in the autochthonous fish species Barbus meridionalis collected in the river Fluvià (NE Catalunya, Spain) after an oil spillage. Four different locations were sampled, including the impacted site, upstream and downstream sites and a reference site. Biomarker responses were compared with diatom and macroinvertebrate community assemblage metrics (Specific Pollution Sensitivity index - IPS, and Iberian Biological Monitoring Working Party - IBMWP, respectively). Chemical analyses denoted that polycyclic aromatic hydrocarbon levels in sediment were much higher at the impacted site than in downstream reaches. Four fold increase of EROD activity together with increased levels of biliary FACs in barbs collected at the spilled site indicated exposure of inhabiting fish to the oil. Additionally, CAT activity was significantly depressed (four fold) when compared to other stations, thus suggesting that fish collected from the impacted sites could be more susceptible to suffer oxidative stress. Biological indices (particularly that of the diatom community IPS) showed slight significant effects between control and impacted sites, indicating that more tolerant taxa were favoured because of the oil spillage. These results support the need to include biochemical responses measured in local species in monitoring programmes aimed to diagnose specific pollution effects in stressed river ecosystems.     

Oxidative stress, liver biotransformation and genotoxic effects induced by copper in Anguilla anguilla L.--the influence of pre-exposure to beta-naphthoflavone

Fish are exposed in the aquatic ecosystems to different classes of pollutants. Polycyclic aromatic hydrocarbons (PAHs) and heavy metals represent two important classes of aquatic contaminants. Thus, one lot of European eels (Anguilla anguilla L.) was pre-exposed during 24 h to 2.7 microM beta-naphthoflavone (BNF; a PAH-like compound), and subsequently exposed during 24 h to 0, 1 and 2.5 microM copper (Cu). Additionally, another lot not pre-exposed to BNF was exposed to the same Cu concentrations. BNF pre-exposure promoted a significant increase in liver ethoxyresorufin O-deethylase (EROD) activity, but did not change the other responses investigated in eels. On the other hand, both Cu concentrations did not modify the liver EROD activity either in eels pre-exposed to BNF or not. Liver total cytochrome P450 was increased in eels exposed to Cu 2.5 microM, being significantly only in eels not pre-exposed to BNF. Free sulfhydryl group content was decreased by 1 and 2.5 microM in eels pre-exposed to BNF or not pre-exposed, being significant at 2.5 microM Cu in eels not pre-exposed compared to its control. Liver total glutathione (TG), reduced glutathione (GSH) and GSH/oxidized glutathione (GSSG) levels were slightly decreased by 1 and 2.5 microM Cu in eels pre-exposed to BNF, whereas a slight tendency to increase was observed in eels not pre-exposed. Thus, liver TG and GSH significantly decreased in 2.5 microM Cu BNF pre-exposed eels compared to eels not pre-exposed to BNF. Liver glutathione reductase and catalase activities were significantly inhibited by 1 and 2.5 microM Cu in eels pre-exposed to BNF, concomitantly with a slight liver glutathione peroxidase tendency to decrease. Lipid peroxidation was significantly increased by 1 microM Cu in eels either pre-exposed or not pre-exposed to BNF. Liver H(2)O(2) was significantly increased by 1 microM Cu in eels pre-exposed to BNF. Liver DNA integrity was significantly decreased by 1 and 2.5 microM Cu in eels pre-exposed to BNF. The oxidative stress and genotoxic effects induced by Cu in eels pre-exposed to BNF revealed that the metal effects are potentiated by previous exposure to BNF.