Acute effects of diclofenac on zebrafish: Indications of oxidative effects and damages at environmentally realistic levels of exposure

With the increasing awareness about the contamination of the aquatic environment by pharmaceuticals, there is a growing need to study their adverse effects on aquatic organisms. Diclofenac is a non-steroidal anti-inflammatory drug (NSAID), whose wide use contributes for its presence in freshwater ecosystems, increasing the probability of causing deleterious changes in aquatic biota. This study evaluated possible oxidative stress effects in Danio rerio embryos and larvae when exposed to a range of ecologically relevant concentrations of diclofenac. It was possible to conclude that diclofenac caused a scenario of oxidative stress, since all tested toxicological parameters were responsive to the drug. In general, diclofenac caused not only significant anti-oxidant adaptive responses for most levels of exposure, but also peroxidative damage. This work evidenced the responsiveness of D. rerio towards diclofenac in environmentally relevant concentrations, which shows that these organisms might face a scenario of oxidative stress in their natural habitat.     

Redox proteomic analysis of mytilus edulis gills: effects of the pharmaceutical diclofenac on a non‐target organism

Veterinary and human pharmaceuticals are an emerging category of chemical pollutants with potential to cause serious toxicity to non‐target organisms. Filter‐feeding aquatic organisms such as mussels are especially threatened. In this study, the blue mussel, Mytilus edulis, was exposed to two doses (0.2 mg/L and 1 mg/L) of the anti‐inflammatory diclofenac. Effects on the gill, the principal feeding organ of mussels, were investigated. It was noted that, while no effect was evident on gill glutathione transferase or catalase activities, there was a tissue‐specific increase in glutathione reductase activity and reduction in total protein thiol groups. Two dimensional electrophoresis was performed and some affected proteins identified by in‐gel tryptic digestion and peptide mass fingerprinting. Of these, four unique proteins (caspase 3/7‐4, heat‐shock cognate protein 70, a predicted enolase‐like protein, arginine kinase) were found to be oxidized whilst eight unique proteins (β‐tubulin, actin, isocitrate dehydrogenase, arginine kinase, heavy metal‐binding HIP, cytosolic malate dehydrogenase, proteasome subunit alpha type 2, Mg: bb02e05 (glyceraldehyde‐3‐phosphate dehydrogenase) and superoxide dismutase) were found to have altered abundance. In addition, bioinformatic analysis suggested putative identities for six hypothetical proteins which either were oxidized or decreased in abundance. These were; 78 kDa glucose‐regulated protein precursor, α‐enolase, calreticulin, mitochondrial H + ‐ATPase, palmitoyl protein thioesterase 1 and initiation factor 5a. It is concluded that diclofenac causes significant oxidative stress to gills and that this affects key structural, metabolic and stress‐response proteins. Copyright © 2015 John Wiley & Sons, Ltd.     

Histological endpoints and oxidative stress transcriptional responses in the Mediterranean mussel Mytilus galloprovincialis exposed to realistic doses of salicylic acid

Despite the availability of analytic data, little is known about the toxicity of salicylic acid (SA) on aquatic non-target organisms. The present study aimed at evaluating the impact of SA through a short-term exposure of the Mediterranean mussel Mytilus galloprovincialis to five environmentally relevant concentrations of SA. A set of suitable biomarkers was applied at selected time-points on mussel digestive glands, including histological observations and expression of oxidative stress related genes. The obtained results showed a conspicuous hemocytic infiltration among mussel digestive tubules, as confirmed also by a flow cytometric approach that revealed an increase of halinocytes and granulocytes. Interestingly, a significant dose and time dependent decrease in the expression levels of oxidative stress related genes was found in mussels exposed to SA except for the glutathione S-transferase gene that was significantly up-regulated in a time-dependent manner confirming its important role against oxidant species and in the metabolism of pharmaceuticals.     

Cyto‐genotoxicity and oxidative stress in common carp (Cyprinus carpio) exposed to a mixture of ibuprofen and diclofenac

Thirty million people worldwide consume each day nonsteroidal anti‐inflammatory drugs (NSAIDs), a heterogeneous group of pharmaceuticals used for its analgesic, antipyretic, and anti‐inflammatory properties. Recent studies report high NSAID concentrations in wastewater treatment plant effluents, in surface, ground, and drinking water, and in sediments. NSAIDs are also known to induce toxicity on aquatic organisms. However, toxicity in natural ecosystems is not usually the result of exposure to a single substance but to a mixture of toxic agents, yet only a few studies have evaluated the toxicity of mixtures. The aim of this study was to evaluate the toxicity induced by diclofenac (DCF), ibuprofen (IBP), and their mixture on a species of commercial interest, the common carp Cyprinus carpio. The median lethal concentration of IBP and DCF was determined, and oxidative stress was evaluated using the following biomarkers: lipid peroxidation and activity of the antioxidant enzymes superoxide dismutase, catalase and glutathione peroxidase. Cyto‐genotoxicity was evaluated by micronucleus test, comet assay, and the specific activity of caspase‐3. Results show that DCF, IBP, and a mixture of these pharmaceuticals induced free radical production, oxidative stress and cyto‐genotoxicity in tissues of C. carpio. However, a greater effect was elicited by the mixture than by either pharmaceutical alone in some biomarkers evaluated, particularly in gill. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1637–1650, 2017.     

The use of biochemical responses to assess ecotoxicological effects of Pharmaceutical and Personal Care Products (PPCPs) after injection in the mussel Elliptio complanata

A biomarker approach was undertaken using the mussel Elliptio complanata to assess the ecotoxicological effects after injection of a range concentration (0–10 mM) of three different PPCPs: carbamazepine, caffeine, methotrexate; and an effluent extract (C8) from St. Lawrence wastewaters treatment plant (Montreal, Canada). A battery of biomarkers, involving oxidative stress and genotoxicity responses: glutation-S-transferase (GST), ethoxyresorufin O-deethylase (EROD), dibenzylflourescein dealkylase (DBF), xanthine oxidoreductase (XOR) activities, lipid peroxidation (LPO) and DNA damage were determined in gonad and digestive gland tissues after 48 h of injection. Results showed an induction of the oxidative metabolism with increasing pharmaceutical concentration in those mussels injected with the PPCPs and the effluent extract. Phase I detoxification enzymes were significantly induced (p < 0.05), concretely DBF activity was significantly induced after caffeine, carbamazipine and C8 injection; and EROD activity after C8 and methotrexate injection. Oxidative stress induction only lead to lipid peroxidation (p < 0.05) in organisms injected with carbamazepine and caffeine and DNA damage in organisms injected with methotrexate (p < 0.05). EROD and DBF enzymatic activities have been found to be suitable biomarkers to determine bioavailability of pharmaceuticals. LPO and DNA damage to determine possible associated adverse effects. Nevertheless, their validation in realistic exposure scenarios and under exposure conditions should be performed in future research.     

Waterborne gemfibrozil challenges the hepatic antioxidant defense system and down-regulates peroxisome proliferator-activated receptor beta (PPARbeta) mRNA levels in male goldfish (Carassius auratus)

The lipid regulator gemfibrozil (GEM) is one of many human pharmaceuticals found in the aquatic environment. We previously demonstrated that GEM bioconcentrates in blood and reduces plasma testosterone levels in goldfish (Carassius auratus). In this study, we address the potential of an environmentally relevant waterborne concentration of GEM (1.5 microg/l) to induce oxidative stress in goldfish liver and whether this may be linked to GEM acting as a peroxisome proliferator (PP). We also investigate the autoregulation of the peroxisome proliferator-activated receptors (PPARs) as a potential index of exposure. The three PPAR subtypes (alpha, beta, and gamma) were amplified from goldfish liver cDNA. Goldfish exposed to a concentration higher (1500 microg/l) than environmentally relevant for 14 and 28 days significantly reduce hepatic PPARbeta mRNA levels (p<0.001). Levels of CYP1A1 mRNA were unchanged. GEM exposure significantly induced the antioxidant defense enzymes catalase (p<0.001), glutathione peroxidase (p<0.001) and glutathione-S-transferase (p=0.006) but not acyl-CoA oxidase or glutathione reductase. As GEM exposure failed to increase levels of thiobarbituric reactive substances (TBARS), we conclude that a sub-chronic exposure to GEM upregulates the antioxidant defense status of the goldfish as an adaptive response to this human pharmaceutical.     

Embryonic development,locomotor behavior,biochemical, and epigenetic effects of the pharmaceutical drugs paracetamol and ciprofloxacin in larvae and embryos of Danio rerio when exposed to environmental realistic levels of both drugs

For several years, the scientific community has been concerned about the presence of pharmaceuticals in the wild, since these compounds may have unpredictable deleterious effects on living organisms. Two examples of widely used pharmaceuticals that are present in the environment are paracetamol and ciprofloxacin. Despite their common presence in the aquatic environment due to their poor removal by sewage treatment plants, knowledge concerning their putative toxic effects is still scarce. This work aimed to characterize the effects of paracetamol (0.005, 0.025, 0.125, 0.625, and 3.125 mg/L) and ciprofloxacin (0.005, 0.013, 0.031, 0.078, 0.195, and 0.488 μg/L) in zebrafish embryos and larvae, exposed to environmentally relevant levels, close to the real concentrations of these pharmaceuticals in surface waters and effluents. The adopted toxic end points were developmental, a behavioral parameter (total swimming time), and a biomarker‐based approach (quantification of the activities of catalase, glutathione‐S‐transferase, cholinesterases, glutathione peroxidase, and lipid peroxidation levels) combined with epigenetic analysis (immunohistochemical detection of 5‐methylcytidine). Exposure to paracetamol had effects on all of the adopted toxic end points; however, ciprofloxacin only caused effects on behavioral tests and alterations in biomarkers. It is possible to ascertain the occurrence of oxidative stress following exposure to both drugs, which was more evident regarding paracetamol, an effect that may be related to the observed epigenetic modifications.     

Neurotoxic,biotransformation, oxidative stress and genotoxic effects in Astyanax altiparanae (Teleostei,Characiformes) males exposed to environmentally relevant concentrations of diclofenac and/or caffeine

The present study evaluated neurotoxic, biotransformation, genotoxic and antioxidant responses to relevant environmental concentrations of diclofenac (0.4 μg L⁻¹) and caffeine (27.5 μg L⁻¹), separate and combined, in adult males of the freshwater fish Astyanax altiparanae after a subchronic exposure (14 days). Fish exposed to diclofenac and caffeine, both separate and combined, revealed a neurotoxic effect through the inhibition of acetylcholinesterase activity in the muscle, while diclofenac alone and in combination caused cyclooxygenase inhibition. Caffeine alone produces genotoxicity on this species but, when combined with diclofenac, it potentiates hepatic lipoperoxidation and the inhibition of oxidative stress enzymes, while diclofenac alone or in combination produces a general inhibition of important enzymes. This study suggests that aquatic contamination produced by these pharmaceuticals has the potential to affect homeostasis and locomotion in A. altiparanae and compromise their immune system and general health.     

A multi-biomarker approach in cross-transplanted mussels Mytilus galloprovincialis

The present work integrates the active biomonitoring (ABM) concept in mussels Mytilus galloprovincialis from the South coast of Portugal transplanted during 28 days between two sites with different sources of contamination, and vice versa, in order to assess biological effects in these mussels. For that purpose a multibiomarker approach was used. The suit of biomarkers indicative of metal contamination were metallothioneins (MT) and the enzyme δ-aminolevulinic acid dehydratase (ALAD), for organic contamination mixed function oxidase system (MFO), glutathione-S-transferase (GST) and acetylcholinesterase (AChE), as oxidative stress biomarkers superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and lipid peroxidation (LPO). These biomarkers were used to determine an index to evaluate the stress levels in these two sites. Site A is strongly influenced by metallic contamination, with higher Cu, Cr and Pb in M. galloprovinciallis, as well as higher MT levels, antioxidant enzymes activities and LPO concentrations, and lower ALAD activity. In site B organic compounds (PAHs) are prevalent and native mussels show higher activities of the MFO system components and GST. Transplanted mussels had significant alterations in some biomarkers that reflect the type of contaminants present in each site, which demonstrates the primary role of the environment in determining the physiological characteristics of resident mussels. Therefore the application of ABM using a battery of biomarkers turns out to be a useful approach in sites where usually complex mixtures of contaminants occurs. In this study the biomarkers that better differentiate the impact of different contaminants at each site were MT, CYP450, SOD and CAT.     

Sea ducks and aquaculture: the cadmium connection

Elevated concentrations of cadmium have been reported in the kidneys of sea ducks that forage along the Pacific Northwest, and cadmium has been postulated as a possible cause of population declines. The blue mussel (Mytilus spp.) which occurs in dense numbers on aquaculture structures and are a primary prey item for sea ducks also contain elevated cadmium concentrations. To determine if foraging on mussels associated with aquaculture structures could pose a toxicological risk to sea ducks, amounts of cadmium ingested per body weight per day by a representative sea duck species, the surf scoter (Melanitta perspicillata), were estimated and compared to the reported avian cadmium NOAEL (no observable adverse effect level) and LOAEL (lowest observable adverse effect level). Results indicate that in some locations within the Pacific Northwest, sea ducks could be exposed to toxicologically significant levels of cadmium associated with mussels foraged from aquaculture structures. This raises the possibility that such exposure could be contributing to observed population declines in these species.     

Protective effects of antioxidants on acrylonitrile‐induced oxidative stress in female F344 rats

The induction of oxidative stress and damage appears to be involved in acrylonitrile induction of brain astrocytomas in rat. The present study examined the effects of dietary antioxidant supplementation on acrylonitrile‐induced oxidative stress and oxidative damage in rats in vivo. To assess the effects of antioxidants on biomarkers of acrylonitrile‐induced oxidative stress, female F344 rats were provided with diets containing vitamin E (0.05%), green tea polyphenols (GTP, 0.4%), N‐acetyl cysteine (NAC, 0.3%), sodium selenite (0.1mg/kg), and taurine (10g/kg) for 7 days, and then co‐administered with 0 and 100 ppm acrylonitrile in drinking water for 28 days. Significant increase in oxidative DNA damage in brain, evidenced by elevated 8OHdG levels, was seen in acrylonitrile‐exposed rats. Supplementation with vitamin E, GTP, and NAC reduced acrylonitrile‐induced oxidative DNA damage in brain while no protective effects were seen with the selenium or taurine supplementation. Acrylonitrile increased oxidative DNA damage, measured by the fpg‐modified alkaline Comet assay in rat WBCs, which was reduced by supplementation of Vitamin E, GTP, NAC, selenium, and taurine. In addition to stimulation of oxidative DNA damage, acrylonitrile triggered induction of pro‐inflammatory cytokines Tnfα, Il‐1β, and Ccl2, and the growth stimulatory cyclin D1 and cyclin D2 genes, which were effectively down‐regulated with antioxidant treatment. Antioxidant treatment also was able to stimulate the pro‐apoptotic genes Bad, Bax, and FasL and DNA repair genes Xrcc6 and Gadd45α. The results of this study support the involvement of oxidative stress in the development of acrylonitrile‐induced astrocytomas and suggest that antioxidants block acrylonitrile‐mediated damage through mechanisms that may involve in the suppression of inflammatory responses, inhibition of cell proliferation and stimulation of apoptosis. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1808–1818, 2016.     

Sublethal toxicity of quinalphos on oxidative stress and antioxidant responses in a freshwater fish Cyprinus carpio

Extensive use of quinalphos, an organophosphorus pesticide, is likely to reach the aquatic environment and thereby posing a health concern for aquatic organisms. Oxidative stress and antioxidant responses may be good indicators of pesticide contamination in aquatic organisms. The data on quinalphos induced oxidative stress and antioxidant responses in carps are scanty. This study is aimed to assess the two sublethal concentrations of quinalphos (1.09 and 2.18 μL L^?1) on oxidative stress and antioxidant responses of Cyprinus carpio for a period of 20 days. In liver, the malondialdehyde level was found to be significantly increased in both the concentrations. The results of the antioxidant parameters obtained show a significant increase in superoxide dismutase, catalase, and glutathione‐S‐transferase activity in liver of fish. These results demonstrate that environmentally relevant levels of the insecticide quinalphos can cause oxidative damage and increase the antioxidant scavenging capacity in C. carpio. This may reflect the potential role of these parameters as useful biomarkers for the assessment of pesticide contamination. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1399–1406, 2016.     

Oxido‐inflammatory responses and histological alterations in rat lungs exposed to petroleum product fumes

Petroleum products—petrol, kerosene, and diesel—composed of volatile organic constituents contribute to air pollution. Exposure of gas station attendants (GSAs) to petroleum products fumes (PPFs) may account for occupation‐related predisposition to respiratory toxicity and disease pathogenesis. We simulated GSA exposure to PPF inhalation and examined their effect on oxido‐inflammatory responses, toxicity, and histopathological alterations in rat lungs, following 8‐hours daily exposure for 60 and 90 days. Reactive oxygen and nitrogen species (RONS), oxidative stress and inflammatory biomarkers, namely: superoxide dismutase (SOD), reduced glutathione (GSH), glutathione peroxidase (GPx), glutathione‐S‐transferase (GST), TNF‐α, IL‐1β, xanthine oxidase (XO), nitric oxide (NO) activity were evaluated. Besides, histopathological examination of the lungs and trachea of exposed rats, PPF exposure resulted in significant (P < .05) increases in RONS, biomarkers of oxidative stress, pro‐inflammation cytokines, and reduced (P < .05) GSH levels in rats, secondary to histopathological alteration in lungs and trachea cytoarchitecture examined in an exposure‐duration‐dependent manner. We conclude, therefore, that the observed biochemical and histological changes create a microenvironment that is permissive to diseases pathogenesis of the respiratory system via oxido‐inflammatory mechanistic pathways.     

Translational responses and oxidative stress of mussels experimentally exposed to Hg, Cu and Cd: one pattern does not fit at all

Certain metals, like Hg, Cu and Cd, are capable of down-regulating protein synthesis in several marine organisms, including Mytilus galloprovincialis. Nevertheless, due to the complexity of the environmental stress, it is difficult to evaluate the influence of individual metals on protein synthesis via field studies. To bypass this difficulty, experimental studies were carried out on M. galloprovincialis exposed in aquarium for 15 days to one of three selected metal salts, HgCl(2), CuCl(2) and CdCl(2). Polysome profile was determined in digestive gland extracts of the exposed mussels as a way of measuring the functional status of ribosomes, superoxide radical production and lipid peroxidation as indicators of oxidative stress, metallothionein content as a metal detoxification index, and superoxide dismutase activity as a free radicals-scavenging index. Exposure of mussels to Hg(2+) or Cu(2+) resulted in a concentration- and time-dependent decrease in the polysome content of digestive gland cells, which at 15th day of exposure and at the highest metal concentrations tested, was 32% and 19% of the control, respectively. Both metals, at the concentrations used (<40 μg/L), did not significantly influence the oxidative stress biomarkers. By contrast, Cd(2+) treatment significantly induced superoxide radical production and lipid peroxidation in digestive gland cells, hinting that mussels suffered from oxidative stress. Polysome levels in Cd(2+)-exposed mussels were initially decreased by day 5 in digestive gland cells and then elevated to reach nearly the control levels by 15 days of exposure. Elevated protein synthesis was associated with significantly increased production of metallothioneins, whereas such increase was not recorded in Hg(2+)- or Cu(2+)-exposed mussels. Interestingly, the ribosome efficiency at initiating protein synthesis followed a similar pattern of polysome alterations, a fact suggesting that regulation of protein synthesis mainly occurred at the initiation phase of translation. Overall, these results suggest that the effect of each metal on protein synthesis is idiosyncratic and depends on its ability to induce specific cellular defense mechanisms against oxidative stress.     

Influence of prenatal maternal stress on the immunocompetence of the offspring.

To evaluate the effects of prenatal maternal stress on the development of humoral immunocompetence in the offspring and on their hormonal and immunologic responses to postnatal stress, gravid Sprague-Dawley rats were exposed daily on gestational days 15-21 to prenatal environmental stress [(PES) 15 unsignaled, inescapable electric foot-shocks (0.05 mA for 0.5 s)] or prenatal psychological stress [(PPS) pregnant rats were placed in the nonelectrified section of the apparatus and allowed to see, hear, and smell a nonpregnant partner being environmentally stressed]. Pregnant controls (PC) were placed in the apparatus for 30 min. Serum corticosterone (CCS) and immunoglobulin G (IgG) levels were measured in the offspring every 7 days from birth to postnatal day (PND) 28. On PND 29-33, offspring were environmentally stressed; hormonal and immune status were determined on PND 34. Levels of IgG were reduced in PES and PPS offspring on PND 0 and in PES offspring on PND 7 and 28. These changes were unrelated to differences in CCS and did not reflect altered maternal-pup interactions or nutritional factors. Postnatal stress was immunosuppressive in PC pups but did not alter immune parameters in PPS offspring. In PES females, postnatal stress was also immunosuppressive. However, in PES males with already reduced IgG levels postnatal stress enhanced immune function. These data provide the first experimental evidence that prenatal maternal stress can alter immune parameters in the rat offspring.     

Genotoxic effects in fish induced by pharmacological agents present in the sewage of some Italian water‐treatment plants

The presence of pharmaceutical substances in the municipal effluents is currently considered the principal source of bio‐active molecule emissions into aquatic environments. This study analyzes the genotoxic damage caused by gemfibrozil and atorvastatin, two regulators of the hematic level of lipids, and sildenafil citrate, a vasodilator, on the teleost Danio rerio. The genotoxicity of these three compounds was evaluated using the comet assay, diffusion assay, and RAPD‐PCR. The alkaline version (pH 12.1) of the comet assay was used for the erythrocytes of the zebrafish to evaluate the presence of single strand DNA breaks. Furthermore, the diffusion assay was used to estimate the number of apoptotic cells. The fish were treated with the three pharmacological agents at the average concentrations previously found at some Italian treatment plants and were then sacrificed from 5 to 35 days after exposure. The data of the comet assay showed a statistically significant loss of DNA integrity after 5 days of exposure to atorvastatin and after one week of exposure to gemfibrozil. This damage was, however, repaired after 14 days. Sildenafil citrate produced, instead, a statistically significant loss of DNA integrity at the concentrations found only after 35 days of exposure. The genotoxicity at the molecular level was tested by RAPD‐PCR. The results from this investigation are in agreement with those from two other tests, confirming the efficacy of the use of the three experimental approaches for the complete evaluation of genotoxic damage. © 2010 Wiley Periodicals, Inc. Environ Toxicol, 2012.     

Effect of a human pharmaceutical carbamazepine on antioxidant responses in brain of a model teleost in vitro: an efficient approach to biomonitoring

Residual pharmaceuticals are generally recognized as relevant sources of aquatic environmental pollutants. In this study, the effects of carbamazepine (CBZ) on the antioxidant defense system in the brain of rainbow trout in vitro were studied. The brain homogenates were incubated with various concentrations of CBZ (1.0 µg l^?1, 0.2 mg l^?1 or 2.0 mg l^?1) for 0, 60, 120 min. After incubation, oxidative stress indices (lipid peroxidation and carbonyl protein), antioxidant enzymes (superoxide dismutase, glutathione reductase and glutathione peroxidase) and nonenzymatic antioxidant (reduced glutathione) in each samples were measured. Based on the results, the brain homogenates performed adaptive responses to CBZ‐induced stress at environmental concentration (1.0 µg l^?1). With increased CBZ concentrations (0.2 or 2.0 mg l^?1), oxidative stress was apparent as reflected by the significant higher levels of oxidative indices, together with the significant inhibition of all antioxidant enzymes activities and reduced glutathione content. Compared with previous studies in vivo, the brain homogenates showed more sensitive antioxidant responses to CBZ stress. In conclusion, the brain homogenates of rainbow trout could be used as an efficient model system in aquatic risk assessment, but more detailed laboratory studies are needed before these findings could be established as special biomarkers for monitoring residual pharmaceuticals in aquatic environment. Copyright © 2010 John Wiley & Sons, Ltd.     

Sub‐Chronic Exposure to Methylmercury at Low Levels Decreases Butyrylcholinesterase Activity in Rats

Abstract: In this study, we examined the effects of low levels and sub‐chronic exposure to methylmercury (MeHg) on butyrylcholinesterase (BuChE) activity in rats. Moreover, we examined the relationship between BuChE activity and oxidative stress biomarkers [δ‐aminolevulinic acid dehydratase (δ‐ALA‐D) and malondialdehyde levels (MDA)] in the same animals. Rats were separated into three groups (eight animals per group): (Group I) received water by gavage; (Group II) received MeHg (30 μg/kg/day) by gavage; (Group III) received MeHg (100 μg/kg/day). The time of exposure was 90 days. BuChE and ALA‐D activities were measured in serum and blood, respectively; whereas MDA levels were measured in plasma. We found BuChE and ALA‐D activities decreased in groups II and III compared to the control group. Moreover, we found an interesting negative correlation between plasmatic BuChE activity and MDA (r = ?0.85; p < 0.01) and a positive correlation between plasmatic BuChE activity and ALA‐D activities (r = 0.78; p < 0.01), thus suggesting a possible relationship between oxidative damage promoted by MeHg exposure and the decrease of BuChE activity. In conclusion, long‐term exposure to low doses of MeHg decreases plasmatic BuChE activity. Moreover, the decrease in the enzyme is strongly correlated with the oxidative stress promoted by the metal exposure. This preliminary finding highlights a possible mechanism for MeHg to reduce BuChE activity in plasma. Additionally, this enzyme could be an auxiliary biomarker on the evaluation of MeHg exposure.     

Oxidative stress biomarkers in Cyprinus carpio exposed to commercial herbicide bispyribac‐sodium

Cyprinus carpio were exposed under field conditions to 20.87 µg l^?1 of commercial herbicide bispyribac‐sodium (Nominee®, SC), during 7, 21 and 72 days. Enzymatic parameters such as catalase (CAT), glutathione S‐transferase (GST) and acetylcholinesterase (AChE) activities, as well as thiobarbituric acid‐reactive substances (TBARS) and protein carbonyl contents were studied in different tissues. After 7 days of exposure, GST activity decreased. At the same period, brain AChE activity increased, but a reduction of activity was observed in muscle tissue. Brain TBARS levels increased at 7 days. After 21 days of exposure liver CAT levels and muscle AChE activities decreased. In the same period, liver protein carbonyl and muscle TBARS increased. After 72 days of exposure in the field, AChE activity was reduced in both brain and muscle. Protein carbonyl contents in liver and brain TBARS levels increased. Muscle AChE activity, TBARS and protein carbonyl can be used as biomarkers of exposure to the herbicide bispyribac‐sodium. This study demonstrates effects of exposure to bispyribac‐sodium under rice field conditions on oxidative stress parameters in tissues of Cyprinus carpio. Copyright © 2010 John Wiley & Sons, Ltd.