The bioaccumulation of waterborne zinc in tissues of silver catfish (Rhamdia quelen) and its effect on biochemical parameters.

Silver catfish (Rhamdia quelen) is a fish species with neotropical distribution, and is a potential model organism to study polluted environment. The aim of this study is to analyze the response of silver catfish to environmental concentrations of waterborne zinc (Zn) over 96 h. Significant metal accumulation was seen in gill, intestine and liver tissues. No significant accumulation was seen in muscle tissue. Lipid peroxidation increased in the brain, and decreased in the muscle and liver at all levels of exposure. Zinc exposure led to decreased protein carbonyl levels in the brain and increased levels in the liver. The activity of catalase in the liver was reduced for all exposed groups. Glutathione S-transferase activity decreased in the brain at the highest level of exposure and in the liver at all Zn concentrations tested. Non-protein thiols increased in the muscle and in the gills after exposure. Ascorbic acid levels increased in the brain and in the gills. Exposure to Zn also altered the metabolic parameters, causing decreased lactate and ammonia levels in the muscle, and decreased glycogen in the liver. Zinc exposure increased ammonia and amino acid levels in the liver, and increase glycogen and amino acid levels in muscle tissue. Our results demonstrate that exposure to environmentally relevant concentrations of Zn led to accumulation of metals in the tissues of silver catfish, with significant changes in biochemical parameters.

Integrated biomarkers response confirm the antioxidant role of diphenyl diselenide against atrazine.

Atrazine (ATZ) is a herbicide worldwide used. That can cause oxidative damage in non-target organisms, such as fish. Furthermore, the threat of exposure to pesticides together with poor nutrition is hazardous to the normal development of fish, and supplementation of the fish diet with antioxidants compounds is an alternative approach to prevent the hazardous effects of pesticide exposure. Here we aimed to investigate the capacity of diphenyl diselenide (PhSe)2 diet supplementation to improve the antioxidant defense of Cyprinus carpio (carp) exposed to environmental concentrations of ATZ. To prove the efficiency of (PhSe)2, we used the Integrated Biomarkers Response (IBR) methodology. Therefore, carp were fed for 8 weeks diets either with or without (PhSe)2 and exposed to 2 or 10µg/L of ATZ for 96h, euthanized, and their liver, gills, and muscle tissues were removed for biochemical assays. ATZ was able to cause oxidative damage from reactive species production in all tissues of carp, as observed by the increase of lipid peroxidation and protein damage. The activity of some antioxidant enzymes was inhibited in carp exposed to ATZ. However, (PhSe)2 supplementation was able to prevent this ATZ-induced damage by improving the activities of antioxidant enzymes and through antioxidant competence of (PhSe)2per se. Furthermore, IBR was shown to be a useful tool to compare treatments, even at different concentrations, and identify the efficiently antioxidant behavior of the organoselenium compound.

Azadirachtin, a neem-derived biopesticide, impairs behavioral and hematological parameters in carp (Cyprinus carpio).

Azadirachtin (Aza) is a promisor biopesticide used in organic production and aquaculture. Although this compound is apparently safe, there is evidence that it may have deleterious effects on fish. Behavioral and hematological tests are grouped into a set of parameters that may predict potential toxicity of chemical compounds. Here, we investigate the effects of Aza, in the commercial formulation Neenmax™ , on carp (Cyprinus carpio) by defining LC50 (96 h), and testing behavioral and hematological parameters. In our study, LC50 was estimated at 80 µL/L. We exposed carp to Aza at 20, 40, and 60 µL/L, values based on 25, 50, and 75% of LC50 , respectively. At 60 µL/L, Aza promoted significant changes in several parameters, increasing the distance traveled and absolute turn angle. In addition, the same concentration decreased the time spent immobile and the number of immobile episodes. Hematological parameters, such as hematocrit, hemoglobin, hematimetrics index, and red cell distribution, were decreased at 60 µL/L Aza exposure. In conclusion, our study demonstrates that 60 µL/L Aza altered locomotor activity, motor pattern, and hematological parameters, suggesting potential toxicity to carp after acute exposure. In addition, this is the first report that evaluates the actions of a chemical contaminant using automated behavioral tracking of carp, which may be a useful tool for assessing the potential toxicity of biopesticides in conjunction with hematological tests. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1381-1388, 2016.

Effect of diphenyl diselenide diet supplementation on oxidative stress biomarkers in two species of freshwater fish exposed to the insecticide fipronil.

The ability of diphenyl diselenide [(PhSe)2] to attenuate oxidative damage was evaluated in the liver, gills, brain, and muscle of carp (Cyprinus carpio) and silver catfish (Rhamdia quelen) experimentally exposed to fipronil (FPN). Initially, the fish were fed a diet without (PhSe)2 or a diet containing 3.0 mg/kg of (PhSe)2 for 60 days. After the 60-day period, the fish were exposed to 0.65 µg/L of FPN for 192 h. The results showed that carp exposed to FPN and not fed with (PhSe)2 exhibited acetylcholinesterase (AChE) inhibition in brain and muscle, and increased thiobarbituric acid-reactive substance (TBARS) in liver, gills, and brain. Furthermore, FPN decreased nonprotein thiols (NPSH) and δ-aminolevulinate dehydratase (δ-ALA-D) in carp liver and gills, and increased plasma glucose and protein levels. In silver catfish, FPN inhibited AChE and increased TBARS levels in muscle. In addition, glutathione S-transferase (GST) decreased in liver and muscle, and plasma glucose was increased. (PhSe)2 reversed some of these effects. It prevented the increase in TBARS levels in liver, gills, and brain in carp and in silver catfish muscle, and reversed the increase in plasma glucose levels in both species. Additionally, (PhSe)2 increased the NPSH levels in carp and silver catfish that had decreased in response to FPN exposure. However, (PhSe)2 was not effective in reversing the AChE inhibition in brain and muscle or the δ-ALA-D decrease in carp liver. Thus, (PhSe)2 protects tissues of both species of fish, mainly by preventing or counteracting the effects of FPN, on TBARS levels, antioxidants, and present anti-hyperglycemic property.

Early biochemical biomarkers for zinc in silver catfish (Rhamdia quelen) after acute exposure.

Contamination of aquatic ecosystems by metals causes various biochemical changes in aquatic organisms, and fish are recognized as indicators of environmental quality. Silver catfish were exposed to six concentrations of zinc (Zn): 1.0, 2.5, 5.0, 7.5, 10.0 and 12.5 mg/L for 96 h to determine the mean lethal concentration (LC50). The value obtained was 8.07 mg/L. In a second experiment, fish were exposed to concentrations of 1.0 or 5.0 mg/L Zn and a control for 96 h. Afterward, the tissues were collected for biochemical analysis. Lipid peroxidation, as indicated by thiobarbituric acid-reactive substance (TBARS), decreased in the liver and brain for all Zn concentrations tested, while in the gills TBARS levels increased at 1.0 mg/L and declined at 5.0 mg/L. Zn increased protein carbonyls in the muscle of silver catfish and decreased it in the other tissues. The enzyme superoxide dismutase increased in both exposed groups. However, catalase did not change. Glutathione S-transferase decreased in the liver and increased in the gills (1.0 mg/L), muscle (5.0 mg/L) and brain (1.0 and 5.0 mg/L). Nonprotein thiols changed only in brain and muscle tissue. Zn exposure inhibited acetylcholinesterase (AChE) activity in the brain at both concentrations tested, but did not change it in muscle. Exposure to Zn inhibited the activity of Na(+)/K(+)-ATPase in the gills and intestine at both concentrations tested. Our results demonstrate that Zn alters biochemical parameters in silver catfish and that some parameters such as AChE and Na(+)/K(+)-ATPase could be considered as early biomarkers of waterborne Zn toxicity.

Exposure to different glyphosate formulations on the oxidative and histological status of Rhamdia quelen.

Due to the wide use of glyphosate (GLY) in soybean cultivation, their residues in the environment may affect non-target organisms such as fish, developing toxic effects. Despite GLY being widely used in Brazil, there are few studies comparing the effects of commercial formulations in native freshwater fish species. Silver catfish (Rhamdia quelen) were exposed to three different commercial formulations of GLY 48% (Orium(®), Original(®) and Biocarb(®)) at 0.0, 2.5 and 5.0 mg/L for 96 h. The effects in thiobarbituric acid-reactive substances (TBARS), catalase (CAT), superoxide dismutase (SOD), glutathione-S-transferase (GST) and histological alterations were analysed in the liver, whereas alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were studied in the plasma. In the liver, TBARS levels increased and CAT decreased in all treatments and herbicides tested in comparison with the control group. The SOD increased at 2.5 mg/L of Orium(®), Original(®) and 5.0 mg/L Orium(®) and Biocarb(®), whereas GST increased at 2.5 mg/L Orium(®) and decreased at 2.5 mg/L Biocarb(®) when compared to the control group. The main histopathological alterations in hepatic tissue were vacuolisation, leucocyte infiltration, degeneration of cytoplasm and melanomacrophage in all GLY treatments. The ALT decreased after exposure to 2.5 mg/L of Biocarb(®) and AST increased at 2.5 mg/L of Orium(®), Original(®) and 5.0 mg/L of Biocarb(®) in comparison with the control group. In summary, the oxidative damage generated by GLY may have caused the increased formation of free radicals that led to the histological alterations observed in hepatocytes.

How we enhanced medical academics skills and reduced social inequities using an academic teaching program.

The training of future physicians should be concurrent with the development of different skills and attitudes. This warrants the need to regularly provide students with opportunities for self-development throughout their academic career. This approach was exemplified in a medical school in the Brazilian Amazon, where students were allowed to play the role of high school teachers. As part of this exercise, they conducted reinforcement classes for high school students to increase the number of university admissions. The medical students were solely responsible for organizing and implementing this project, giving them the opportunity to develop teaching and leadership skills, enhance their understanding of communication and administration and contribute toward the society.

Integrated assessment of biomarker response in carp (Cyprinus carpio) and silver catfish (Rhamdia quelen) exposed to clomazone.

Clomazone is considered a potential contaminant of groundwater and is persistent in the environment. To verify the effects of clomazone in Cyprinus carpio and Rhamdia quelen, a method that combines biomarker responses into an index of "integrated biomarker response" (IBR) was used for observed biological alterations in these species. Thiobarbituric acid-reactive substances in liver of carp and silver catfish decreased at both concentrations tested. However, in muscle it increased in carp at 3 mg/L and silver catfish at 6 mg/L. Protein carbonyl increased in liver (3 and 6 mg/L) and muscle (6 mg/L) of carp. In carp, superoxide dismutase (SOD) increased at 3 mg/L and catalase at 6 mg/L. In silver catfish, SOD in liver decreased at 3 mg/L. Glutathione-S-transferase increased at 3 mg/L in muscle of carp. Nonprotein thiol levels decreased at both concentrations in liver of silver catfish and muscle of carp. In silver catfish, acetylcholinesterase (AChE) decreased in brain at 6 mg/L. Nevertheless, AChE in muscle of both species increased at 3 and 6 mg/L. IBR was standardized scores of biomarker responses and was visualized using star plots. The IBR values shown that in carp there was predominantly an induction of parameters, whereas in silver catfish there was inhibition of these responses. In this way, IBR may be a practical tool for the identification of biological alterations in fish exposed to pesticides. In the present study, IBR was efficient for comparisons of fish species using clomazone. This study may serve as a base for evaluation of other pesticides in the rice field, environment, or laboratory experiment.

Commercial formulation containing 2,4-D affects biochemical parameters and morphological indices of silver catfish exposed for 90 days.

The objective of this study was to verify whether a commercial formulation of 2,4 dichlorophenoxyacetic acid [2,4-D dimethylamine salt (DMA)] affects the growth and biochemical parameters of silver catfish (Rhamdia quelen) after 90 days of exposure. The fish exposed to 0.5 or 2.0 mg/L of DMA presented exhibited decreased growth parameters. Glucose was reduced in the mucus layer at both concentrations, and the total protein level was increased at the highest concentration tested. Fish exposed to DMA showed reduced liver and kidney glycogen at both concentrations tested, while in the muscle, glycogen was reduced only at 2.0 mg/L. Glucose was increased in the liver and decreased in the muscle and kidney at both concentrations and was not altered in the plasma. Lactate was increased in all the tissues and decreased in the plasma. Protein levels were reduced in the liver and plasma at both concentrations, while in the muscle, it was decreased at a concentration of 2.0 mg/L. Levels of thiobarbituric acid-reactive substances were reduced in the liver and increased in the muscle at both concentrations and did not change in the brain. DMA increased catalase activity in the liver at both concentrations tested. The present study demonstrates the effects of long-term exposure to DMA. Some parameters could be used as toxicity indicators to identify the presence of DMA in an aquatic environment.

Alterations in carbohydrate and protein metabolism in silver catfish (Rhamdia quelen) exposed to cadmium.

Changes in carbohydrate and protein metabolism were studied in silver catfish Rhamdia quelen exposed to cadmium (0; 0.236 or 0.414 mg/L) during 7 and 14 days. After exposure time the fish were exposed to recovery period (water without cadmium), during 7 and 14 days. Different alterations in the metabolic parameters were observed such as an increase in lactate, protein, amino acid and ammonia levels as well as a reduction in glucose values after the exposure periods in liver. In muscle, glycogen and glucose values enhanced after cadmium exposure at both concentrations for 7 days; however, at 0.414 mg/L cadmium, protein levels decreased while amino acids and ammonia levels enhanced. An increase in the lactate values was found in plasma after 7 days of exposure and a reduction in the lactate, glucose and protein levels occurred after 14 days of exposure. Results indicated that the metabolic alterations after cadmium exposure were dependent on the tissue type and exposure time. Cadmium exposure for 14 days and recovery period also of 14 days seem to be less harmful to the liver and muscle. However, even after recovering from some changes, fish health may be affected making them more sensitive to some environmental changes.

Carbofuran promotes biochemical changes in carp exposed to rice field and laboratory conditions.

Effects of carbofuran commercial formulation on oxidative stress parameters were studied in carps (Cyprinus carpio) exposed to 50µg/L for 7 and 30 days under rice field and laboratory conditions. Thiobarbituric acid reactive substance (TBARS) levels were increased in the brain of fish after 7 and 30 days under rice field and laboratory conditions. In the liver and muscle, TBARS levels increased after 7 and 30 days under laboratory conditions, whereas in rice field the levels increased only after 30 days. Protein carbonyl content in the liver increased after 7 and 30 days under both experimental conditions. Acetylcholinesterase (AChE) activity was decreased in the brain and muscle after 7 and 30 days under both experimental conditions evaluated. The superoxide dismutase (SOD) activity increased in the liver after 7 and 30 days under rice field condition, whereas under laboratory condition this enzyme increased only after 30 days. The catalase (CAT) activity in the liver decreased after 30 days under rice field condition, whereas no changes were observed under laboratory conditions. In rice field, glutathione S-transferase (GST) decreased after 7 days but increased after 30 days, whereas no change was observed in fish exposed to carbofuran under laboratory conditions. These results suggest that environmental relevant carbofuran concentrations may cause oxidative stress, affecting biochemical and enzymatic parameters on carps. Some parameters could be used as biomarkers to carbofuran exposure.

Evaluation of the effects induced by dietary diphenyl diselenide on common carp Cyprinus carpio.

Several diets employed in aquaculture are enriched with selenium (Se), as it is a fundamental element to aquatic vertebrates. Diphenyl diselenide [(PhSe)2], which is a synthetic organoselenium compound, has been considered a potential antioxidant agent in different experimental models. Thus, the aim of this study was to evaluate the effects of dietary diphenyl diselenide at concentrations of 1.5, 3.0, and 5.0 mg/kg for 60 days and to determine its optimal supplemental level for carp, Cyprinus carpio. Neither growth retardation nor hepatoxicity was induced by the inclusion of diphenyl diselenide at concentrations ranging from 1.5 to 5.0 mg/kg. In addition, the inclusion of 3.0 mg/kg of diphenyl diselenide stimulated the weight and length of the carp. The supplementation with 1.5 and 3.0 mg/kg of diphenyl diselenide did not produce oxidative damage in the tissues, verified by peroxidation lipid and protein carbonyl assays. However, at 5.0 mg/kg, it caused an increase of the lipid peroxidation in the liver, brain, and muscle, and inhibited the cerebral acetylcholinesterase activity. An increase of the hepatic superoxide dismutase activity and non-protein thiols content in all tissues and ascorbic acid in the liver, gills, and brain was verified in carp fed with the diet containing 3.0 mg/kg of diphenyl diselenide. This diet had advantageous effects for the fish used in experiments. Therefore, this compound could be considered a beneficial dietary supplement for carp nutrition.

Exposure to sublethal concentrations of copper changes biochemistry parameters in silver catfish, Rhamdia quelen, Quoy & Gaimard.

The effects of Cu exposure on catalase (CAT) and acetylcholinesterase (AChE) activity, formation of thiobarbituric acid-reactive species (TBARS) and metabolic parameters were evaluated in silver catfish (Rhamdia quelen). The fish were exposed for 45 days to 0, 16 and 29 µg/L Cu. The fish that were exposed to Cu exhibited lower TBARS levels in the muscle and higher TBARS levels in the liver. They also showed lower CAT activity in the liver and lower AChE activity in the brain and muscle. Higher glucose and lactate and lower protein plasma levels were observed in the fish exposed to Cu. The changes in the hepatic metabolic parameters were Cu concentration dependent. In the muscle, lower glycogen and higher lactate levels were observed in the fish exposed to Cu. Alterations in the metabolic parameters showed a preference for the anaerobic pathway of energy production and liver protein catabolism to supply the energy demand.

Herbicide clomazone effects on δ-aminolevulinic acid activity and metabolic parameters in Cyprinus carpio.

The objective of this study was to investigate δ-aminolevulinic acid (δ-ALA-D) activity and metabolic parameters of Cyprinus carpio exposed to clomazone herbicide. Fish were exposed 2.5, 5, 10 and 20 mg L(-1) of clomazone for 192 h. Results indicated that δ-ALA-D activity was decreased in the gills at concentrations of 5 and 10 mg L(-1). Liver glycogen increased, while muscle and gill glycogen levels decreased at 5, 10 and 20 mg L(-1). Glucose was increased in the gills and plasma. Lactate decreased in the gills and liver and increased in the muscle. Protein and amino acids levels increased in the liver and gills and decreased in the muscle. At a clomazone concentration of 20 mg L(-1), ammonia increased in the gills and muscle and decreased in the liver. The results indicated that the metabolic parameters of glycogen, lactate, protein and amino acids in liver, muscle and gills, blood glucose levels, and the enzyme δ-ALA-D in gills may be useful indicators of clomazone toxicity in carp.

Toxic effects of penoxsulam herbicide in two fish species reared in southern Brazil.

Toxic effects of penoxsulam herbicide on acetylcholinesterase, thiobarbituric acid-reactive substances and protein carbonyl were studied in silver catfish (Rhamdia sp.) and carp (Cyprinus carpio). Acetylcholinesterase activity was inhibited in both brain and muscle tissue, with the inhibition being greater in carp than in silver catfish. The levels of malondialdehyde (MDA), an indicator of lipid peroxidation, decreased in silver catfish brain tissue, but increased in the carp brain. MDA also increased significantly in muscle tissue of silver catfish. The levels of protein carbonyl, another measure of oxidative damage, increased in the brain of both fish species, and in the muscle of carp. However, silver catfish exhibited a decrease in muscle protein carbonyl. It appears that silver catfish may possess better mechanisms of defense against penoxsulam toxicity than carp.

Caenorhabditis elegans as a suitable model to evaluate the toxicity of water from Rolante River, southern Brazil.

Urbanization and agricultural activities increased environmental contaminants. Integrated analysis of water parameters and bioassays represents an essential approach to evaluating aquatic resource quality. This study aimed to assess water quality by microbiological and physicochemical parameters as well as the toxicological effects of water samples on the Ames test and Caenorhabditis elegans model. Samples were collected during (collection 1) and after (collection 2) pesticide application in the upper (S1), middle (S2), and lower (S3) sections of the Rolante River, southern Brazil. Metals were determined by GFAAS and pesticides by UPLC-MS/MS. Bioassays using the Ames test and the nematode C. elegans were performed. Levels of microbiological parameters, as well as Mn and Cu were higher than the maximum allowed limits established by legislation in collection 2 compared to collection 1. The presence of pesticide was observed in both collections; higher levels were found in collection 1. No mutagenic effect was detected. Significant inhibition of body length of C. elegans was found in collection 1 at S2 (P < 0.001) and S3 (P < 0.001) and in collection 2 at S2 (P = 0.004). Comparing the same sampling site between collections, a significant difference was found between the site of collection (F(3,6)=8.75, P = 0.01) and the time of collection (F(1,2)=28.61, P = 0.03), for the S2 and S3 samples. C. elegans model was useful for assessing surface water quality/toxicity. Results suggest that an integrated analysis for the surface water status could be beneficial for future approaches.

Oxidative stress in carp exposed to quinclorac herbicide under rice field condition.

This study evaluated parameters of oxidative stress and antioxidant profile in fish after herbicide exposure. Cyprinus carpio were exposed to quinclorac (initial concentration 344.60µg/L) for 7, 30, and 90 days under rice field condition. Thiobarbituric acid-reactive substances (TBARS) were evaluated in brain, liver and muscle tissues, and protein carbonyl in liver. Enzymatic parameters such as catalase (CAT) and gluthatione S-transferase (GST) activities also were studied in liver. TBARS levels fluctuated in the brain showing increase in 7 days and decrease in 30 days, while in liver it was observed increase in 7 and 30 days, as well as in muscle after 30 and 90 days. The protein carbonyl was also increased after 30 and 90 days of herbicide exposure. CAT and GST activities were decreased after 30 and 90 days, respectively. The alterations observed suggest that a commercial formulation containing quinclorac causes oxidative damage in different tissues of carp after a long time of exposure. This study pointed out the importance of quinclorac toxicity considering the concentration used in rice fields.

The effects of diphenyl diselenide on oxidative stress biomarkers in Cyprinus carpio exposed to herbicide quinclorac (Facet®).

The occurrence of pollutants in the aquatic environment can produce severe toxic effects on non-target organisms, including fish. These sources of contamination are numerous and include herbicides, which represent a large group of toxic chemicals. Quinclorac, an herbicide widely applied in agriculture, induces oxidative stress due to free radical generation and changes in the antioxidant defense system. The aim of this study was to assess if dietary diphenyl diselenide (PhSe)2 has a protective effect in tissues of fish species Cyprinus carpio exposed to the quinclorac herbicide. The fish were fed with either a standard or a diet containing 3.0 mg/Kg of diphenyl diselenide for 60 d. After were exposed to 1 mg/L of Facet® (quinclorac commercial formulation) for 192 h. At the end of the experimental period, parameters as thiobarbituric acid-reactive substance levels (TBARS), protein carbonyl, catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase (GST), nonprotein thiols (NPSH) and ascorbic acid in the liver, gills, brain and muscle were evaluated in Cyprinus carpio. In fish exposed to quinclorac and feeding with standard diet TBARS levels increased in liver and gills. However, SOD activity decreases in liver whereas no alterations were observed in catalase activity in this tissue. Quinclorac also decrease GST activity in liver and brain, NPSH in brain and muscle and ascorbic acid in muscle. Concerning protein carbonyl exposed to herbicide the fish did not show any alterations. The diphenyl diselenide supplemented diet reversed these effects, preventing increases in TBARS levels in liver and gills. GST activity was recovered to control values in liver. NPSH levels in brain and muscle increased remain near to control values. These results indicated that dietary diphenyl diselenide protects tissues against quinclorac induced oxidative stress ameliorating the antioxidant properties.

Tissue biochemical alterations of Cyprinus carpio exposed to commercial herbicide containing clomazone under rice-field conditions.

Field and laboratory experiments were performed to evaluate toxicological responses of Cyprinus carpio exposed to the commercial herbicide clomazone (500 mg l(-1)). Fish were exposed to 0.5 mg l(-1) of the formulated herbicide for 7, 30, and 90 days. Fish were exposed to clomazone in field conditions (7, 30, or 90 days trapped in submersed cages together with rice crops) and in laboratory conditions where the fish were placed in 45-l tanks with tap water only for 7 days. Fish exposed for 7, 30, or 90 days showed no alterations in acetylcholinesterase (AChE) activity under field conditions. Under laboratory conditions, decreased muscle AChE activity was observed only after 7 days of exposure. During the same evaluation period (7 days), oxidative stress parameters changed under both field and laboratory conditions; however, metabolic parameters were altered only under field conditions. Disorders in oxidative stress parameters and metabolism were evident in different tissues up to day 90 after treatment. These overall results show that AChE activity changed only under laboratory conditions. Oxidative stress, along with metabolic parameters, may be good indicators of herbicide contamination in C. carpio under rice-field conditions.

Toxicological responses of Cyprinus carpio exposed to the herbicide penoxsulam in rice field conditions.

Cyprinus carpio fish were exposed to penoxsulam (Ricer) in field conditions. The experiment in the rice field was carried out for 7, 21 and 72 days. Oxidative stress parameters and antioxidant profile were studied. The acetylcholinesterase (AChE) enzyme activity in the brain was increased after 7 days and reduced after 21 and 72 days of the experiment in the rice field. The AChE activity in muscle was reduced only after 72 days of exposure. Thiobarbituric acid-reactive species were increased in the liver, brain and muscle at 7 days of the trial, reduced at 21 days in the brain and unaltered after 72 days of exposure in muscle. However, an increase in this parameter in the brain and liver was observed. Liver glutathione S-transferase was reduced at 7 days, unchanged at 21 days and increased after 72 days of exposure. Catalase of the liver changed only in the second experimental period, when it was reduced. Liver protein carbonyl was reduced at 7 days and increased at 21 and 72 days of exposure. This study shows long-term effects of rice herbicide at environmentally relevant concentrations on toxicological parameters in different tissues (brain, muscle and liver) of Cyprinus carpio.