Effects of Copper and Cadmium on Lipogenic Metabolism and Metal Element Composition in the Javelin Goby (Synechogobius hasta) After Single and Combined Exposure

The present study was performed to determine the effects of single and combined exposure of copper (Cu) and cadmium (Cd) on lipogenic metabolism and metal element composition of javelin goby Synechogobius hasta. Two hundred and forty uniform-sized S. hasta (initial mean weight 20.3 ± 0.3 g [mean ± SEM throughout]; initial body length 15.2 ± 0.2 cm) were randomly assigned to 12 fiberglass tanks (water volume 300 l) with 20 fish/tank. The fish were exposed to four treatments with different Cu and Cd concentration for 30 days, respectively: (1) control (without extra Cu and Cd addition), (2) Cu (nominal concentrations of 77 μg/l), (3) Cd (79 μg/l), and (4) Cu + Cd (Cu/Cd coexposure). Growth decreased, but hepatosomatic index, viscerosomatic index, and lipid content increased after metal exposure. Staining with Oil Red O and haematoxylin and eosin showed extensive alterations in liver of metals-exposed fish. Metal exposure influenced the accumulation of metal elements (Cu, Cd, iron, zinc, and manganese) in several tissues (muscle, gill, intestine, liver, and spleen) and increased hepatic 6-phosphogluconate dehydrogenase, glucose-6-phosphate dehydrogenase, malic enzyme, isocitrate dehydrogenase, and fatty acid synthase activities. The results of the present study indicated that the changes in lipogenic metabolism and metal element compositions of fish under Cu and Cd coexposure could not be explained by synergism of the addition of the effects observed in singly Cu- or Cd-exposed fish. To our knowledge the present study, for the first time, investigated the effects of Cu and Cd coexposure on hepatic lipogenic metabolism and metal element compositions in a wide range of tissues and organs in fish, which provided new evidence for Cu and Cd interactions in fish.     

Effect of waterborne zinc exposure on metal accumulation, enzymatic activities and histology of Synechogobius hasta

The present study was conducted to determine the metal accumulation, antioxidant enzymatic response, hepatic intermediary metabolism and histological changes in Synechogobius hasta exposed to 0.35 (control), 9.7 and 19.2 mg/L Zn, respectively, on the 0, 4th, 8th and 12th day. Waterborne Zn exposure significantly reduced hepatosomatic index, hepatic lipid contents and fatty liver occurrence rate, increased Zn, Fe and Mn contents and reduced the contents of Cu and Ca in liver, and increased muscle Zn content. Waterborne Zn exposure also significantly influenced enzymatic activities involved in antioxidant responses (superoxide dismutase, catalase, glutathione-S-transferase, malondialdehyde) in liver and spleen, and changed hepatic intermediary enzymatic activities (succinate dehydrogenase, malic dehydrogenase, lactate dehydrogenase, lipoprotein lipase, hepatic lipase), impaired the histological structure of the gill and spleen, and reduced vacuolated hepatocytes. Thus, our study demonstrated for the first time that waterborne Zn exposure could reduce fatty liver syndrome in S. hasta.     

Antioxidant responses, hepatic intermediary metabolism, histology and ultrastructure in Synechogobius hasta exposed to waterborne cadmium

The present study was conducted to determine antioxidant responses, hepatic intermediary metabolism, histology and ultrastructure in Synechogobius hasta after a 15-days of waterborne cadmium (Cd) exposure at the concentrations of 0 (control), 0.10, 0.17 and 0.29 mg Cd/l (corresponding to 0, 12.6%, 21.5% and 36.7% of 96 h LC₅₀), respectively. Growth performance and survival declined, but hepatosomatic index (HSI) increased with increasing waterborne Cd levels (P<0.05). Waterborne Cd exposure also significantly increased lipid contents in whole body and liver (P<0.05), and Cd accumulation in whole body, muscle and vertebrae. Waterborne Cd exposure changed hepatic enzymatic activities involved in intermediary metabolism, induced antioxidant responses and increased lipid peroxidation level in the gill, liver and spleen. Waterborne Cd exposure also caused considerable histological alterations of gill, liver and spleen, led ultrastructures damage of liver and spleen of fish, and induced fatty liver for this fish species.     

Protective Effects of Calcium Pre-Exposure Against Waterborne Cadmium Toxicity in Synechogobius hasta

The present study was performed to evaluate the effects of calcium (Ca) pre-exposure and then waterborne cadmium (Cd) exposure on metal element accumulation, enzymatic activities, histology, and ultrastructure in Synechogobius hasta and test the hypothesis that Ca could protect against Cd-induced toxicity in the fish species. Three hundred sixty fish [initial mean weight 25.5 ± 0.1 g (mean ± SEM)] were stocked in 18 circular fiberglass tanks (water volume: 300 l), 9 of which were pre-exposed to Ca at a rate of 400 mg Ca/l for 9 days and then exposed to concentrations of 0, 79.3, and 158.6 μg Cd/l for 9 days. Another 9 tanks were cultured in natural seawater (no extra Ca addition) for 9 days and then exposed to concentrations of 0, 79.3, and 158.6 μg Cd/l for 9 days. Both Ca pre-exposure and then waterborne Cd exposure influenced the accumulation of metal elements [cadmium (Cd), copper, zinc, and iron] in several tissues (muscle, gill, liver, spleen, and intestine), changed hepatic intermediary metabolism, and induced histological and ultrastructural alterations in tissues. In general, Ca pre-exposure seemed to mitigate the severity of Cd-induced mortality and histopathological injuries indicating that Ca pre-exposure had the capacity to decrease Cd toxicity in S. hasta.     

Protective effects of calcium on copper toxicity in Pelteobagrus fulvidraco: copper accumulation, enzymatic activities, histology

The present study was conducted to determine interactive effects of waterborne co-exposure of copper (Cu) and calcium (Ca) on Cu accumulation, enzymatic activities and histology in yellow catfish Pelteobagrus fulvidraco and test the prediction that Ca could protect against Cu--induced toxicity in the fish species. Yellow catfish were exposed to 0, 1.0, 2.0 mg Cu/l, in combination with 0 and 50 mg Ca/l. Waterborne Cu and Ca co-exposure influenced the majority of tested enzymatic activities (succinate dehydrogenase, malic dehydrogenase, lactate dehydrogenase, lipoprotein lipase and hepatic lipase), and changed Cu contents in several organs (gill, liver, kidney, gastrointestine and muscle). For histological observations, at the same Ca level, waterborne Cu exposure induced injuries in gills and liver. However, Ca addition seemed to mitigate the severity of Cu--induced injuries. Thus, our study demonstrated that Ca had the capacity to reduce Cu toxicity in P. fulvidraco.     

In Vitro Effects of Selenium on Copper-Induced Changes in Lipid Metabolism of Grass Carp (Ctenopharyngodon idellus) Hepatocytes

The present study was performed to evaluate the in vitro effects of selenium (Se) supplementation to prevent copper (Cu)-induced changes in lipid metabolism of hepatocytes from grass carp (Ctenopharyngodon idellus). Four groups (control and 100 μM Cu in combination with 0, 5, and 10 μM Se, respectively) were chosen. Compared with the control, activities of glucose 6-phosphatedehydrogenase, 6-phosphogluconate dehydrogenase, malic enzyme, and carnitine palmitoyltransferase I (CPT I) of all three Cu-exposed groups at 24 and 48 h were significantly greater. However, among three Cu-exposed groups, increasing Se concentration tended to increase activities of G6PD and ME at 24 h and 6PGD activity at 24 and 48 h but decreased CPT I activity at 24 h. Compared with the control, Cu exposure alone, or in combination with Se, downregulated mRNA levels of sterol regulatory element-binding protein-1 (SREBP-1c), fatty acid synthase (FAS), acetyl-CoA carboxylase, peroxisome proliferator activated receptor alpha (PPARα), CPT I, and hormone-sensitive lipase (HSL) at 24 h as well as SREBP-1c, FAS, and ACC mRNA levels at 48 h. However, upregulated mRNA levels of PPARα, CPT I, and HSL, as well as decreased triglyceride content, were recorded at 48 h. Thus, although toxic at greater levels, lower levels of Se provided significant protection against Cu-induced changes in lipid metabolism. For the first time, our study indicates the dose- and time-dependent effects of Se addition on changes in lipid metabolism induced by Cu in fish hepatocytes and provides new insights into Se–Cu interaction at both enzymatic and molecular levels.     

Tissue-Specific Antioxidant Responses in Pale Chub (Zacco platypus) Exposed to Copper and Benzo[a]pyrene

In this study, antioxidant responses including lipid peroxidation (LPO), superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST), were evaluated in the liver, gill and muscle tissues of pale chub (Zacco platypus) exposed to copper (Cu) and benzo[a]pyrene (BaP). Cu exposure induced significant antioxidant responses in Z. platypus, particularly in the liver, whereas BaP exposure had a negligible effect. Following Cu exposure, both SOD and CAT activity increased in a concentration-dependent manner, showing significant correlations with malondialdehyde (MDA) levels as a measure of LPO (r = 0.646 and 0.663, respectively). SOD, CAT and GST mRNA levels were also enhanced following Cu exposure, except at 20 μg L^?1, although significant correlations with antioxidant enzyme activities were not found. The results of this study suggest that combined information on SOD and CAT activities together with LPO levels in the liver could be a useful indicator for assessing oxidative stress in freshwater fish.     

Influence of dietary lipid on lipogenic enzyme activities in coho salmon, Oncorhynchus kisutch (Walbaum).

Coho salmon (Oncorhynchus kisutch), 8 to 18 months of age, were maintained in culture tanks and were fed three semipurified diets. The diets contained 40% of energy from protein and 11.5%, 23%, or 46% of energy from lipid. The body weight gain and food conversion factors were similar among groups of fish fed the diets in each of the three experiments. Wet weight of mesenteric adipose tissue increased with increased amount of lipid in the diet; however, epaxial muscle lipid content was not influenced by the lipid content of the diet. Several hepatic and adipose tissue lipogenic enzymes (fatty acid synthetase, citrate cleavage enzyme, malic enzyme, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and NADP-isocitrate dehydrogenase) were assayed. These lipogenic enzymes exhibited high activities in liver and relatively low concentration in adipose tissue of the fish. The activities of all the hepatic lipogenic enzymes assayed, except for NADP-isocitrate dehydrogenase, were depressed as the level of lipid in the diet was increased; however, the activities of these enzymes in mesenteric adipose tissue were not influenced by the diets fed. The results of this study indicate that dietary lipid depresses hepatic lipogenic enzyme activities and that the liver may be a more important site for fatty acid synthesis than is adipose tissue in coho salmon.     

Response of Antioxidant System of Tilapia (Oreochromis niloticus) Following Exposure to Chromium and Copper in Differing Hardness

Tilapias (Oreochromis niloticus) were exposed to copper or chromium in soft water (SW) (~80 mg CaCO₃/L, conductivity 1.77 mS/cm) or hard water (HW) (~320 mg CaCO₃/L, conductivity 5.80 mS/cm) using 2 exposure protocols (20 μM for 48 h and 10 μM for 144 h). Following the exposures, antioxidant enzyme activities [superoxide dismutase (SOD); catalase (CAT); glutathione peroxidase; glutathione reductase; and glutathione S-transferase (GST)] and glutathione (GSH) levels were measured in the liver of fish. SOD and CAT activities of control fish kept in SW were significantly lower than control fish kept in HW. However, the other antioxidant indices (glutathione metabolism) of both control fish were unaffected from water hardness. Acute metal exposures did not alter the glutathione metabolism, whereas SOD activity in SW and CAT activity in both waters changed significantly. In subchronic duration, Cu exposure caused significant decreases in measured parameters, except for GST activity and GSH level. Similarly, GST activity and GSH level were unaffected from Cr exposure. This study showed that SOD and CAT were the most sensitive antioxidant indices, and that glutathione metabolism, in general, was not altered following metal exposures in different waters.     

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.     

Effects of Copper Oxide Nanoparticles on Antioxidant Enzyme Activities and on Tissue Accumulation of <Emphasis Type="Italic">Oreochromis niloticus</Emphasis>

Accumulation of copper oxide nanoparticles (CuO NPs) in gill, liver and muscle tissues of Oreochromis niloticus and its effects on superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) activities in gill and liver tissues were studied after exposing the fish to 20 µg/L Cu over 15 days. Copper levels and enzyme activities in tissues were determined using spectrophotometric (ICP-AES and UV) techniques respectively. No mortality was observed during the experiments. Copper levels increased in gill and liver tissues of O. niloticus compared to control when exposed to CuO NPs whereas exposure to metal had no effect on muscle level at the end of the exposure period. Highest accumulation of copper was observed in liver while no accumulation was detected in muscle tissue. SOD, CAT activities decreased and GPx activity increased in gill and liver tissues when exposed to CuO NPs.     

The Effects of Chronic Exposure to Environmentally Relevant Levels of Waterborne Cadmium on Reproductive Capacity and Behaviour in Fathead Minnows

Cadmium (Cd) is a priority pollutant in aquatic ecosystems because of its highly toxic effects at low concentrations. Recent work has highlighted that at sublethal concentrations, Cd can impair the ability of fish to respond to important sensory cues. In the present study, we examined whether chronic exposure to environmentally relevant concentrations of waterborne Cd (1, 2.5 and 5 μg/L) can result in reproductive impairment in fathead minnows (Pimephales promelas) as measured by the standard Organization for Economic Cooperation and Development (OECD) 21-day reproductive assay. In addition, we also evaluated the effects of chronic waterborne Cd exposure on Cd accumulation in target tissues (liver and ovary) and plasma estradiol level in females and on the reproductive behaviour of fathead minnows. We found that the standard endpoints used in the OECD reproductive assays (e.g., egg production, number of spawning attempts, brood size) are more sensitive to Cd exposure than behavioural endpoints; however, the traditional method of interpreting reproductive impairment may underestimate toxic effects. Cadmium accumulation in liver and ovary of fish increased with increasing Cd exposure concentrations; however, plasma estradiol level remained unaffected. Reproductive capacity in fathead minnows decreased at waterborne Cd concentrations as low as 1 μg/L. The findings of our study have important implications for understanding the effects of chronic Cd exposure in metal-impacted feral fish populations.     

Alterations of Metabolic Enzymes in Australian Bass, Macquaria novemaculeata, After Exposure to Petroleum Hydrocarbons

Australian bass Macquaria novemaculeata were exposed to the water-accommodated fraction of Bass Strait crude oil, dispersed crude oil, or burnt crude oil to assess sublethal effects of oil spill remediation techniques on fish. Fish were exposed to these treatments for 16 days either through the water column or by way of a pre-exposed diet of amphipod Allorchestes compressa. Fish gills, liver, and white muscle were sampled and cytochrome C oxidase (CCO) and lactate dehydrogenase (LDH) activities quantified. In all treatments containing fish exposed by way of the water column, aerobic activity increased in the gills, whereas a decrease of this enzymic activity was observed in the liver and white muscle. Exposures by way of the food pathway indicated similar trends. Anaerobic (LDH) activity increased in the gills, liver, and white muscle after waterborne exposures. Stimulation in anaerobic activity also occurred in the liver and white muscle of fish after exposure to contaminated food. CCO activity in the gills was the most sensitive biomarker when monitoring waterborne exposures to petroleum hydrocarbons. In the gills, the dispersed oil treatment resulted in the most pronounced biological response, suggesting that in the short term the use of dispersants on an oil slick might cause the most perturbations to fish metabolism.     

Effects of Subchronic Manganese Chloride Exposure on Tambaqui (Colossoma macropomum) Tissues: Oxidative Stress and Antioxidant Defenses

This study aimed to evaluate oxidative stress parameters in juvenile tambaqui (Colossoma macropomum) exposed to 3.88 mg l^?1 Mn²⁺ for 96 hours. Biomarkers of oxidative stress, such as thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), catalase (CAT), and glutathione-S-transferase (GST) activities, as well as content of reduced glutathione (GSH), were analyzed in gill, liver, brain, and kidney. The presence of Mn²⁺ in the water corresponded to increased levels of Mn²⁺ accumulation according to the following sequence: gill > kidney > brain > liver. There was a significant increase in TBARS levels (40 %) and SOD activity (80 %) in addition to a significant decrease in GSH content (41 %) in gills of fish exposed to waterborne Mn²⁺. In hepatic tissue of the exposed animals, TBARS levels decreased significantly (35 %), whereas SOD (82 %) and GST activities (51 %) as well as GSH content (43 %) increased significantly. In brain of exposed juvenile fish, only significant decreases in SOD (32 %) and CAT activities (65 %) were observed. Moreover, the kidney of exposed fish showed a significant increase in TBARS levels (53 %) and a significant decrease in SOD activity (41 %) compared with the control. Thus, the changes in biomarkers of oxidative stress were different in the tissues, showing a specific toxicity of this metal to each organ.     

Combined Effects of Different Food Rations and Sublethal Copper Exposure on Growth and Energy Metabolism in Common Carp

Common carp (Cyprinus carpio) were fed two different rations, 0.5% body weight (low ration; LR) and 5% body weight (high ration; HR), throughout acclimation, sublethal (64 μg/L) Cu exposure for 28 days, and a subsequent 2-week recovery period. Growth, liver water content, and liver energy stores were assessed during this period. Growth rates were elevated in HR fish compared to LR fish, as was the hepatic lipid content. This was associated with a higher water content in the livers of LR fish. Liver glycogen levels were similar in both feeding treatments and remained relatively stable during Cu exposure. Cu exposure caused a significant reduction in growth in both HR and LR fish. Reduction in growth coincided with significant changes in liver and blood composition. Liver lipid levels dropped significantly during the first days of the exposure in both feeding treatments, and the difference between LR and HR lipid levels disappeared during Cu exposure. During the first week of Cu exposure, the difference in liver water content disappeared as well, with a significant reduction of the water levels in the LR fish. A rise of hepatic protein was observed after 2 and 4 weeks of Cu exposure in the LR carp and after 4 weeks of exposure in the HR fish. Cu exposure led to pronounced increases in plasma ammonia concentrations in HR carp. Growth and energy stores recuperated during the 2-week recovery period in both feeding treatments. The observed changes during Cu exposure are probably related to physiological disturbances like hypoxia and stress, as well as an inhibition of ammonia excretion.     

Anti-oxidative Responses on Hepatic Tissue of Zebrafish (<Emphasis Type="Italic">Danio rerio</Emphasis>) in a Short Duration of Sub-lethal Concentrations of Cadmium Exposure

The aim of the present study was to identify whether the responses of oxidative stress in zebrafish liver are similar to those in mammalians upon low doses of Cd²⁺ exposure in short durations. Fish were exposed to 1.78 μM Cd²⁺ (treatment) and 0.0 μM Cd²⁺ (control) for 0, 1, 3, and 6 h. The reactive oxygen species (ROS) and lipid peroxidation (LPO) of hepatic tissues significantly increased after 3 and 6 h of Cd²⁺ exposure, respectively. Antioxidants glutathione peroxidase (gpx1a), superoxide dismutase (sod), and catalase (cat) were up regulated after 1–3 h, and metallothionein isoforms (smtB and mt2) increased after 3–6 h of Cd²⁺ exposure. The caspase-3 and p53 mRNA expressions significantly increased threefolds after 1 h of Cd²⁺ exposure. Results confirmed that oxidative stress in the hepatic tissue was induced by Cd²⁺ within 3 h. However, anti-oxidative functions immediately up regulated, causing cell apoptosis levels to decrease after 6 h of Cd²⁺ exposure.     

Mortality,Oxidative Stress and Hepatotoxicity in Juvenile African Catfish, <Emphasis Type="Italic">Clarias gariepinus</Emphasis> Burchell,Exposed to Lead and Cypermethrin

In this study, juvenile catfish (Clarias gariepinus) were exposed to 2 mg/L Pb, 0.5 μg/L cypermethrin, or both for 96 h. Survival ranged from 100 % in both treatments without cypermethrin, to 50 % in fish exposed to cypermethrin only or the mixture. There were significant decreases in liver lysozyme, γ-glutamyl transpeptidase, and alanine aminotransferase activities in fish exposed to cypermethrin or the mixture. Liver aspartate aminotransferase activity (AST) showed a significant reduction after exposure to Pb or cypermethrin alone, and the effect of the mixture on AST was additive or potentially synergistic. Liver lipid peroxidation (LPO) was increased in fish exposed to the mixture compared to those exposed to cypermethrin only, indicating that Pb presence enhanced LPO caused by cypermethrin. Our study demonstrates the potential for toxic interaction between Pb and cypermethrin in fish and suggests that due to the varying responses to contaminant mixtures in our study, researchers should consider using a variety of biomarkers.     

Effects of Cadmium Exposure on Metal Accumulation and Energy Metabolism of Silver Carp (<Emphasis Type="Italic">Hypophthalmichthys molitrix</Emphasis>)

Effects of cadmium (Cd) exposure on metal accumulation and energy metabolism of silver carp (Hypophthalmichthys molitrix) were studied during 14 days. The results showed that Cd accumulated in tissues of silver carp significantly with time and Cd concentration, as the order: liver?>?kidney?>?gill?>?muscle. The levels of muscle glycogen, triglyceride, and plasma triglyceride decreased significantly (p?<?0.05). The levels of muscle protein, plasma glucose and lactate significantly increased during the first 8 days, and then all significantly decreased (p?<?0.05). No significant alternations were observed in muscle cortisol, ATP and plasma protein (p?>?0.05). The results indicate that the tissues’ Cd concentrations and energy metabolism were altered by the presence of waterborne Cd, and silver carp mobilizes the muscle energy stores to cope with the increased energy demands for detoxication and repair mechanism induced by the exposure to waterborne Cd.     

The assessment of episodic metal pollution. II. The effects of cadmium and copper enriched diets on tissue contaminant analysis in rainbow trout (Oncorhynchus mykiss)

Rainbow trout, Oncorhynchus mykiss, were fed on a commercial feed enriched with either Cd or Cu for 32 days and allowed to recover on normal food for 12 days. The body burden of fish fed Cd-enriched diet increased from about 0.05 to 0.39 g/g wet weight, reflected by elevation in the Cd content of gill, liver, blood plasma, kidney, skin, mucus, and whole gut. Muscle Cd content did not alter. Most organs remained contaminated with Cd after 12 days depuration. The body burden of animals fed Cu-enriched diet increased from about 1.2 to 1.5 g/g wet weight, with the gill, whole gut, blood plasma, skin, and mucus contaminated after 32 days, no changes in the liver and muscle occurred. All organs, except the gill and kidney, returned to control values after 12 days depuration. In exposed animals, 76 and 53% of the Cd or Cu body burden, respectively, were contained in the gut, unlike waterborne exposure. Differences in the body distribution of toxicants after intermittent waterborne and dietary exposure may identify the principal routes of pollutant uptake. Ratios of toxicant concentrations in gill/liver may establish the exposure status of fish, but cannot be used to differentiate dietary and waterborne contamination. Analysis of mucus may identify waterborne Cu exposure; dietary and waterborne contributions to mucus Cd content are more difficult to establish.