Binary effects of fluoxetine and zinc on the biomarker responses of the non-target model organism Daphnia magna.

The antidepressant effect of zinc on mammals has been documented in recent decades, and the concentration of the antidepressant fluoxetine (FLX) in aquatic environments has been rising constantly. The aim of the present study is to evaluate the combined toxicity of a serotonin reuptake inhibitor (FLX) and Zn2+ on a non-target aquatic model organism Daphnia magna. Animals were exposed to single and binary combinations of FLX (20.5 and 41 µg/L for subchronic and 41 and 82 µg/L for acute exposures) and Zn2+ (40 µg/L for subchronic and 80 µg/L for acute exposures). In vivo experiments were done for 7 days subchronic and 48 h acute exposure, while subcellular supernatants of whole Daphnia lysate (WDL) were directly treated with the same concentrations used in the acute experiments. Morphological characteristics, Ca2+-ATPase, antioxidant enzyme activities, and lipid peroxidation were examined. There was antioxidant system suppression and Ca2+-ATPase inhibition despite the diverse response patterns due to duration, concentration, and toxicant type. After acute exposure, biomarkers showed a diminishing trend compared to subchronic exposure. According to integrated biomarker response index (IBR) analysis, in vivo Zn2+ exposure was reasonably effective on the health of D. magna, whereas exposure of WDL to Zn2+ had a lesser impact. FLX toxicity increased in a concentration-dependent manner, reversed by the combined exposure. We concluded that potential pro-oxidative and adverse Ca2+-ATPase effects of FLX and Zn2+ in D. magna may also have harmful impact on ecosystem levels. Pharmaceutical exposure (FLX) should be considered along with their potential to interact with other toxicants in aquatic biota.

A trait-based approach to determine the risks of Zn to the overall health status of native fish species Barbus meridionalis.

Fish adapt to changing environments by maintaining homeostasis or making energy trade-offs that impact fitness. We investigated the effect of Zn on the fitness and physiology of Barbus meridionalis, a native cyprinid fish species, under two exposure scenarios. The Osor stream's mine-effluent reach represented long-term (chronic) exposure, while the upstream reach served as a control/acute exposure. Acute exposure involved exposing B. meridionalis to 1mg/L Zn for 96 h in the laboratory. We examined physiological traits (Standard metabolic rate SMR, Maximum metabolic rate MMR, Absolute Aerobic scope AAS, Critical swimming capacity Ucrit) and antioxidant system, AS (Superoxide dismutase, SOD; Catalase, CAT; Glutathione peroxidase, GPX; Glutathione-S-transferase, GST; Glutathione, GSH; Thiobarbaturic acid reactive substances, TBARS) biomarkers. The results indicated that Zn had no significant effect on osmoregulatory cost (SMR) in either exposure scenario but impaired energetically costly exercise (low MMR). AAS reduction in both exposure groups suggested compromised energy allocation for life-history traits, evidenced by decreased locomotor performance (Ucrit) after acute exposure. Tissue-specific and time-dependent responses were observed for AS biomarkers. The fish exhibited ineffective control of oxidative damage, as evidenced by high TBARS levels in the liver and gills, despite increased CAT and GSH in the liver under acute conditions. Our findings demonstrate differential responses at the subcellular level between the two exposure scenarios, while trait-based endpoints followed a similar pattern. This highlights the utility of a trait-based approach as a supplementary endpoint in biomonitoring studies, which provides insights into impacts on individual fitness and population demography.

The effects of 100 nm pure boron nanoparticles on the primary antioxidant system of Nile tilapia (Oreochromisniloticus).

In this study, the effects of 100 nm boron nanoparticles (B-NPs) on the primary antioxidant status of Nile tilapia were researched via analysis of enzyme activities and related gene expressions. This is a new study which focuses on the relationship between B-NPs and oxidative stress that contribute to the literature in terms of its scope. Fish (n = 15) for each group were exposed to three different concentrations as 5, 25 (n2) and 125 (n3) mg/L during 96 h to see the response of the primary antioxidant system. According to the results, SOD expressions differed in all treatment groups compared to the control group (P < 0.05). CAT expressions were different in 5 and 125 mg/L groups compared to control and 25 mg/L groups (P < 0.05). GPX expressions were only different in 125 mg/L group (P < 0.05). The changes in enzyme activities of SOD and CAT were significantly different in 25 mg/L groups. GPX enzyme activities were not significant (P > 0.05). TBARS concentrations in 25 mg/L group were significantly different from those in the control and 125 mg/L groups (P < 0.05).

Sulfoxaflor, Zn2+ and their combinations disrupt the antioxidant and osmoregulatory (Ca2+-ATPase) system in Daphnia magna.

BACKGROUND: The oxidative- and osmoregulatory stress-inducing potential of binary mixtures of sulfoxaflor (SUL), a recently developed sulfoximine insecticide, and Zn2+ was aimed to evaluate in Daphnia magna with different exposure regimes. METHODS: Animals were exposed to different SUL concentrations (1.25, 2.5, 10, and 25 mg/L) for 7 days. In vivo 48 h and in vitro effects of single and binary mixtures of SUL (25 and 50 mg/L) and Zn2+ (40 µg/L) were also determined. Furthermore, Ca2+-ATPase, oxidative stress biomarkers (catalase, CAT; superoxide dismutase, SOD; glutathione peroxidase, GPX; glutathione S-transferase, GST; reduced glutathione, GSH; thiobarbituric acid reactive substances, TBARS), and morphometric characteristics were measured. RESULTS: Variable response patterns were observed due to exposure duration and regime, toxicant type, and concentration. Marked effects of SUL were observed, especially in subacute exposure, and 25 mg/L SUL concentration can be considered as a threshold level. Stimulation of GST activity was the most typical response, followed by declined SOD activity and GSH levels. GPX activity and TBARS levels responded differently depending upon the exposure type. Subacute and in vitro effects of SUL and Zn2+ produced similar responses except for some cases. Ca2+-ATPase activity was altered differently upon subchronic duration, though inhibited by in vitro SUL+Zn effect. Subchronic SUL exposure increased body weight and length up to 25 mg/L, contrary to the observed decrease at higher concentrations. CONCLUSIONS: Single and binary mixtures of SUL and Zn2+ caused damage to the antioxidant and osmoregulatory system due to their oxidative potential on cellular targets (biomarkers). The current data emphasized that investigating the SUL toxicity with the Zn2+ combination based on the multi-biomarker approach is essential in the realistic evaluation of SUL toxicity in toxicological research.

Evaluation of Oxidative Stress Biomarkers in Brain Metastatic and Non-Metastatic Lung Cancer Patients with Different Cell Types.

BACKGROUND: Oxidative stress that leads to an imbalanced prooxidant/antioxidant status can be a critical factor affecting lung cancer etiopathology. The antioxidant system provides primary protection under oxidative stress. OBJECTIVE: The purpose of the study was to investigate the serum antioxidant system status in brain metastatic and non-metastatic lung cancer patients with different cell types. METHODS: In this prospective study, 33 patients with lung cancer metastasis (metastatic patient group), 36 lung cancer patients (non-metastatic patient group), and 25 healthy control groups were included. Enzymatic (Superoxide Dismutase, SOD; Glutathione Peroxidase, GPX; and Glutathione Reductase, GR) and non-enzymatic (Glutathione, GSH) antioxidant system biomarkers with Thiobarbituric Acid Reactive Substances (TBARS) levels were studied in the serum samples of the control and patient groups. The oxidative stress biomarkers were measured spectrophotometrically. RESULTS: SOD activity increased though TBARS levels and GR activity decreased in both patient groups compared to the control. GPX activity increased only in the non-metastatic group. Antioxidant biomarkers varied between small cell and non-small cell group patients. GR activity and GSH levels were significantly higher in the non-metastatic group compared to the metastatic group. Correlations were also found between antioxidant parameters in the non-metastatic group. CONCLUSION: It was emphasized the imbalanced antioxidant system in the duration of the disease is related to not only cell type but also the metastatic structure. This is the preliminary study exhibiting the contribution of antioxidant imbalance in different subtypes with varied prognosis and behavior of lung cancer in the presence of brain metastasis. Therefore, oxidative stress biomarkers can serve as a useful tool to get information about the progression of lung cancer. Thus, it may provide fundamental data for further cancer research when considering the diagnosis of the disease.

How metals directly affect the antioxidant status in the liver and kidney of Oreochromis niloticus? An in vitro study.

BACKGROUND: Metals can disturb the integrity of physiological and biochemical mechanisms in fish. Thus components of defense as an antioxidant system are significant biomarkers due to their vital role in coping with metal stress. The aim of the current study is to investigate the direct effects of Cd, Cu, and Zn sublethal exposures (in vitro) on the antioxidant system parameters in the liver and kidney of Nile tilapia. METHODS: The antioxidant enzyme activities and GSH levels were analyzed after in vitro sublethal metal (200 and 400 µg/L Cd, Cu, and Zn) treatments of Oreochromis niloticus liver and kidney supernatants. RESULTS: Metals even at lower levels caused significant changes in the levels of antioxidant system parameters due to concentration, metal, and tissue type. GSH metabolism parameters were more responsive to the metal effect. TBARS levels and GPX activity were mostly increased while CAT, SOD, rGSH, and GSH/GSSG levels decreased. The kidney was more affected than the liver in vitro conditions. Cu was more effective in the liver whereas it was Zn for the kidney. Cd caused negative correlations among the antioxidant enzymes. Significant correlations were found between enzymes and GSH levels upon Zn and Cu exposures. CONCLUSIONS: Direct metal effects may trigger different response trends due to their nature and tissue differences. The current data provide a knowledge about which antioxidant biomarkers can define better the oxidative stress caused by direct metal effect for further studies including in vivo experiments.

Antioxidant system status in threatened native fish Barbus meridionalis from the Osor River (Iberian Peninsula): I. Characterization and II. In vitro Zn assays.

The evaluation of antioxidant system capacity is important in aquatic toxicology. It was aimed to characterize the liver antioxidant enzymes (SOD, CAT, GPX, GR, and GST) and to test the in vitro Zn effect (200 and 400 ZnSO4 µg/L) in native fish Barbus meridionalis obtained from the Osor River (NE, Spain) influenced by Zn contamination. The maximal enzyme activities were at pH 7.0-7.5 and 100 mM phosphate buffer. Barbel showed high catalytic activity (high Vmax and low Km) indicating the efficient antioxidant detoxification ability. Direct Zn effect caused an antioxidant system imbalance. Mostly upon lower Zn concentration, GPX activity decreased (95-100 %) though CAT, GR, and GST increased (36-1543 %). GSH values either stimulated (290 %) or inhibited (85-93 %) due to tissue differences. The first record of barbel antioxidant enzyme characterization and in vitro data presenting an unbalanced antioxidant pattern could be significant to evaluate the metal pollution in the Osor River for further in vivo studies.

Antioxidant imbalance in the erythrocytes of Myotonic dystrophy Type 1 patients.

The most common form of muscular dystrophy is known as Myotonic dystrophy Type 1 (DM1) in adults. It was aimed to investigate the relationship between antioxidant imbalance and diaphragm thickness with pulmonary function test results in peripheral blood of Myotonic Dystrophy Type 1 patients. In the prospective study, 33 DM1 and 32 healthy control groups were taken after the ethics committee decision (2018-10529). Antioxidant defence system enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR), glutathione S-transferase (GST) and thiobarbituric acid reactive species (TBARS) levels were studied in blood samples. Also, muscular strength (MRC score), creatine kinase (CK) and diaphragm thicknesses were measured, and pulmonary function tests were performed. Among the studied parameters, TBARS levels and GPX, GR and GST activities in erythrocytes of DM1 patients showed a significant decrease in the range of 29-45% compared to the control group. MRC score, diaphragm thickness and inspiratory function test results at the end of inspiration and expiration were found lower though CK levels were higher in DM1 group. In the patient group, a positive correlation was found between antioxidant parameters (TBARS, CAT and GST) with diaphragm thicknesses and pulmonary function test though GPX showed a negative correlation with them. It was emphasized that the data obtained shows the harmful/pathogenic role of oxidative stress caused by free radicals in DM1, and also provide useful data for the treatment and processes of this disease.

Effects of two different lipid emulsions on antioxidant status, lipid peroxidation and parenteral nutrition- related cholestasis in premature babies, a randomized-controlled study.

BACKGROUND: Olive oil-soybean oil (OO/SO) based lipid emulsions (LE) lack ω-3 PUFAs eicosapentaenoic acid -EPA and docosahexaenoic acid- DHA, which have clinical benefits on inflammatory processes. Fish oil based LEs are good sources of DHA and EPA. Fish oil, MCT, Olive oil and Soya oil (FMOS) lipid is one of the fish oil containing LEs supplemented with high levels of α-tocopherol and lower levels of phytosterol compared to OO/SO lipid emulsions. We investigated the effects of OO/SO and FMOS lipid preparations on cholestasis, levels of antioxidant enzymes and lipid peroxidation. METHODS: Preterm neonates ≤32 gestational weeks age and/or ≤1500 g were randomly assigned to receive either FMOS or OO/SO in the first day of life. Catalase, superoxide dismutase (SOD), glutathione peroxidase (GPx) and thiobarbituric acid reactive substances (TBARS) levels in the first day of life, 7th day of lipid use and 28th day of life were measured and cholestasis during parenteral nutrition was recorded. RESULTS: 34 and 33 patients were in FMOS and OO/SO lipid groups respectively. Although the TBARS levels were higher in the first day of life and 7th day of LEs in OO/SO lipid group (p=0.014 and p=0.022), on the 28th day of life TBARS level was similar and SOD level was higher (p=0.014) in OO/SO group. Cholestasis was significantly lower in FMOS lipid group (0% vs. 18.2%), (p=0.011) and neonates regained birth weight earlier (p=0.006). There was no significant difference in other morbidities. CONCLUSIONS: FMOS and OO/SO lipid emulsions have similar effects on lipid peroxidation on 28th day of life and on morbidities in short term period except for cholestasis.

Response of the antioxidant enzymes of the erythrocyte and alterations in the serum biomarkers in rats following oral administration of nanoparticles.

In this study, Al2O3, CuO and TiO2 nanoparticles (NPs) were administered to mature female rats (Rattus norvegicus var. albinos) via oral gavage (0, 0.5, 5, 50mg/kg b.w./day) for 14days to investigate their effects on 14 serum biomarkers and 4 antioxidant enzyme (catalase, superoxide dismutase, glutathione peroxidase, glutathione S-transferase) activities in the erythrocyte. Data showed that Al2O3 did not cause any significant (P>0.05) change in the parameters, except few cases, while CuO and TiO2 caused significant alterations in antioxidant system parameters of the erythrocytes. Activities of catalase and superoxide dismutase significantly decreased in CuO and TiO2 administered rats. Oppositely, glutathione peroxidase activity increased in CuO and TiO2 administered rats. There were no significant alterations in the activity of glutathione S-transferase in the erythrocytes. Levels of glucose, cholesterol, bilirubin, triglyceride, triiodothyronine (T3), estradiol, prolactin and immunoglobulin M (IgM) in the serum altered after some of NP administrations, whereas cortisol, protein, creatinine, blood urea nitrogen (BUN), thyroxine (T4) and immunoglobulin G (IgG) levels in the serum did not change significantly after any of NP administration. There were outstanding increases in the levels of bilirubin and prolactin and decreases in the levels of triglyceride and estradiol. The present study demonstrated that the antioxidant enzymes in the erythrocyte were generally affected from copper and titanium NPs, while aluminium and copper NPs caused more significant alterations in serum biomarkers.

Characterization and response of antioxidant systems in the tissues of the freshwater pond snail (Lymnaea stagnalis) during acute copper exposure.

The response of enzymatic (superoxide dismutase, SOD; catalase, CAT; glutathione peroxidase, GPX and glutathione reductase, GR) and non-enzymatic responses (glutathione, GSH, oxidized glutathione, GSSG and GSH/GSSG) against acute Cu toxicity (2-90µg/mL for 48h) in different tissues of Lymnaea stagnalis were measured. Incubation conditions for enzymatic activity measurements were optimized for L. stagnalis tissues. Three examined tissues, the hepatopancreas, the foot muscle and the mantle, exhibited variable responses in antioxidant parameters as a function of Cu concentrations. The most responsive antioxidant enzymes were GPX and CAT while GR appeared less sensitive. In general antioxidant enzymes at higher Cu concentrations though GSH levels at lower Cu concentrations exhibited the greatest changes in hepatopancreas and foot muscle, respectively. All antioxidant enzymes except GR increased after exposure to the highest Cu concentration in mantle. Total and reduced GSH increased in hepatopancreas but decreased with GSH/GSSG ratios at all Cu concentrations in foot muscle. The present results show that antioxidants respond to acute Cu exposure at concentrations as low as 2µg Cu/L in adult L. stagnalis with variable responses in different tissues. Antioxidants both including enzymatic and non-enzymatic parameters may account, in part, for the high tolerance to acute metal exposure observed in adult L. stagnalis and could form suited biomarkers to evaluate the metal exposure and toxicity in aquatic environment even at relatively low level short term exposure.

Characterization of antioxidant system parameters in four freshwater fish species.

The potential use of antioxidant system parameters has gained considerable interest due to their pivotal role of detoxification mechanisms in environmental studies and culture fish point of view. Fish with different ecological needs may have different antioxidant capacity and response to environmental contaminants. Thus, the optimal working conditions and specific enzyme activities (Vmax and Km) of antioxidant system parameters (Superoxide dismutase, SOD; Catalase, CAT; Glutathione peroxidase, GPX; Glutathione reductase, GR and Glutathione S-transferase, GST) and glutathione (GSH) were determined in four commonly cultured freshwater fish species (tilapia; Oreochromis niloticus, carp; Cyprinus carpio, trout; Onchorhynchus mykiss and catfish; Clarias garipienus). Data showed that optimal concentrations of different buffers, pH and specific chemicals for each enzyme and GSH were similar in most cases for all fish species, except a few differences. The highest Vmax and Km values were found in carp for GPX and GST, though these values were the highest in tilapia, catfish and trout for CAT, SOD and GR, respectively. As a conclusion, optimization assays of these parameters in different bioindicator organisms based on their physiological and ecological differences may be useful for the aquatic ecosystem biomonitoring studies and also present fundamental data for utilization in aquaculture.

Alterations in the serum biomarkers belonging to different metabolic systems of fish (Oreochromis niloticus) after Cd and Pb exposures.

The serum of vertebrates including human gives sufficient data about the current health status of organism in concern. Biomarkers have gained importance in evaluation of data from biological monitoring studies. In this study, freshwater fish Oreochromis niloticus were individually exposed Cd or Pb using acute (10µM, 2 d) and chronic (20µM, 20 d) exposure protocols to investigate the alterations in serum parameters (ALP, ALT, AST, LDH, lipase, glucose, protein, cholesterol and triglyceride) and response of the endocrine system functioning in different axis, namely HPI (cortisol), HPT (TSH, T3, T4), gonadal (LH, FSH) and prolactin. Data showed that except LH, the levels of all hormones decreased significantly following exposure to Cd and Pb both in acute and chronic exposures. In acute exposures, the activity of ALP and levels of cholesterol and triglyceride decreased significantly following both Cd and Pb exposures, while glucose levels increased only after Cd exposure. In chronic exposures, both metal exposures caused significant decreases in ALP activity and levels of cholesterol and triglyceride, though there were increases in glucose level after Cd exposure and AST, ALT and LDH levels after Pb exposure. Data emphasized the importance of biomarker selection and multiparameter usage of relevant systems in ecotoxicological research to achieve proper evaluation of environmental data.

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.

Investigations on the osmoregulation of freshwater fish (Oreochromis niloticus) following exposures to metals (Cd, Cu) in differing hardness.

Hardness is one of the most important factors in water chemistry as it affects fish physiology and metal toxicity. The aim of this study was to investigate osmoregulatory responses in the Nile tilapia Oreochromis niloticus exposed to copper and cadmium (1.0µg/mL) in soft water (SW) (hardness 80mg CaCO3/L and conductivity 1.77mS/cm) and hard water (HW) (hardness 320mg CaCO3/L and conductivity 5.80mS/cm) for 0, 1, 7 and 14 days. Following the exposures, Na(+)/K(+)-ATPase activity, ion and Cu levels in the gill, kidney and intestine were measured. There was no fish mortality within 14 days, except Cu exposure in SW which killed all fish between 8 and 12 days. Generally, Na(+)/K(+)-ATPase activity was altered by both metal exposures in the gill and kidney as it increased in HW condition, but decreased in SW condition. There were also alterations in Na(+)/K(+)-ATPase activity in the intestine as its activity generally decreased. Data, in general, showed that Cd was more effective on Na(+)/K(+)-ATPase activity comparing to Cu. However, ion levels altered mainly in the kidney and intestine. Tissue metal accumulation was higher in fish tissues from SW condition comparing to HW condition. Data represented here showed that the effects of metals differed in differing water hardness. This suggests that special attention should be paid to the water chemistry when natural monitoring studies are carried out. This study also suggests that the response of osmoregulation system of fish may be a sensitive indicator under stressful conditions in different natural waters.

Response of ATPases in the osmoregulatory tissues of freshwater fish Oreochromis niloticus exposed to copper in increased salinity.

An increase in salinity of freshwater can affect the physiology and metal uptake in fish. In the present study, Nile tilapia Oreochromis niloticus were exposed to copper (1.0 mg/l) in increased salinities (2, 4, and 8 ppt) for 0, 1, 3, 7, and 14 days. Following the exposures, the activities of Na(+)/K(+)-ATPase, Mg(2+)-ATPase, and Ca(2+)-ATPase were measured in the gill, kidney, and intestine to evaluate the changes in osmoregulation of fish. Results showed that increases in salinity and Cu exposure of fish significantly altered the ATPase activities depending on the tissue type, salinity increase, and exposure durations. Salinity-alone exposures increased Na(+)/K(+)-ATPase activity and decreased Ca(2+)-ATPase activity. Na(+)/K(+)-ATPase activity decreased following Cu exposure in 2 and 4 ppt salinities, though the activity increased in 8 ppt salinity. Ca(2+)-ATPase activity decreased in the gill and intestine in all salinities, while the activity mostly increased in the kidney. However, there were great variations in Mg(2+)-ATPase activity following exposure to salinity alone and salinity+Cu combination. Cu accumulated in the gill and intestine following 14 days exposure and accumulation was negatively correlated with salinity increase. Data indicated that ATPases were highly sensitive to increases in salinity and Cu and might be a useful biomarker in ecotoxicological studies. However, data from salinity increased freshwaters should carefully be handled to see a clear picture on the effects of metals, as salinity affects both metal speciation and fish osmoregulation.

The effects of salinity and salinity+metal (chromium and lead) exposure on ATPase activity in the gill and intestine of tilapia Oreochromis niloticus.

Freshwater organisms are highly sensitive to increases in salinity because they causes serious osmoregulation problems. Salinity of inland waters can be increased as a result of anthropogenic activities. In this study, freshwater fish Oreochromis niloticus were exposed individually to increased salinities (0, 2, and 8 ppt) alone and salinity+metal [1 µg/mL chromium (Cr) or lead (Pb) exposure at 2 and 8 ppt] exposures for different time periods (1, 7, and 14 days) to investigate the response of Na(+)/K(+)-ATPase and Mg(2+)-ATPase in the osmoregulatory tissues (gill and intestine). Results showed that enzyme activity varied depending on salinity, tissue, metal, and exposure duration. Metal levels in controls and salinity-exposed groups were lower than the detection limit, although significant Cr and Pb accumulation occurred in the salinity+metal combination groups. In salinity-exposed groups, there were increasing trends in the enzyme activity, whereas there were decreasing trends in the metal+salinity groups. Gill ATPases were more affected by the exposure conditions compared with intestine ATPases. Results showed that salinity+metal exposure both played significant roles on ATPase activities in the osmoregulatory tissues, although the alterations in the activity were mostly insignificant supporting compensation mechanisms. Results also suggest that the osmoregulation of freshwater fish should be investigated in toxicity- monitoring programs in inland waters.

Metals (Ag(+) , Cd(2+) , Cr(6+) ) affect ATPase activity in the gill, kidney, and muscle of freshwater fish Oreochromis niloticus following acute and chronic exposures.

Freshwater fish Oreochromis niloticus were individually acutely exposed to different concentrations (0, 0.1, 0.5, 1.0, and 1.5 µg/mL) of Cd(2+) , Cr(6+) , and Ag(+) for 96 h and 0.05 µg/mL concentration of the same metals for different periods (0, 5, 10, 20, and 30 days) chronically. Following each experimental protocol, Na(+) /K(+) -ATPase, Mg(2+) -ATPase, and Ca(2+) -ATPase activities were measured in the gill, kidney, and muscle of O. niloticus. In vitro experiments were also performed to determine the direct effects of metal ions (0, 0.1, 0.5, 1.0, and 1.5 µg/mL) on ATPases. Except Ag(+) , none of the metals caused fish mortality within 30 days. Silver killed all the fishes within 16 days. Metal exposures generally decreased Na(+) /K(+) -ATPase and Ca(2+) -ATPase activities in the tissues of O. niloticus, although there were some fluctuations in Mg(2+) -ATPase activity. Ag(+) and Cd(2+) were found to be more toxic to ATPase activities than Cr(6+) . It was also observed that metal efficiency was higher in the gill than in the other tissues. Results indicated that the response of ATPases varied depending on metals, exposure types, and tissues. Because ATPases are sensitive to metal toxicity, their activity can give valuable data about fish physiology. Therefore, they may be used as a sensitive biomarker in environmental monitoring in contaminated waters.

Essential metal (Cu, Zn) exposures alter the activity of ATPases in gill, kidney and muscle of tilapia Oreochromis niloticus.

An acute (96 h--0.1, 0.5, 1.0, 1.5 µg/ml) and chronic (up to 30 days--0.05 µg/ml) protocols of Cu and Zn were applied to freshwater fish Oreochromis niloticus to investigate these essential metal effects on the activities of gill, kidney and muscle Na(+)/K(+)-ATPase, Mg(2+)-ATPase and Ca(2+)-ATPase. In vitro effects of both metals (20 min--0.1, 0.5, 1.0, 1.5 µg/ml) were also measured to be able to compare both exposure routes. Data showed that ATPase activities, in general, decreased following all the exposure conditions, though there were some increases especially in Mg(2+)-ATPase activity. Among the enzymes, Na(+)/K(+)-ATPase and Ca(2+)-ATPase appeared to be more sensitive than Mg(2+)-ATPase to the metals. The data also indicated that effects of Cu on ATPase activity in the tissues of O. niloticus were stronger than the effects of Zn, possibly due to higher toxic effects of Cu. In vivo and in vitro exposures of metals showed similar trends with a few exceptions, especially in the gill. Variability of ATPase activity is determined by tissue type, metal species, concentration and duration. This work showed that even essential metals can alter significantly activities of ATPases in fish and thus suggests using them as a sensitive biomarker in metal contaminated waters.

Response of antioxidant system of freshwater fish Oreochromis niloticus to acute and chronic metal (Cd, Cu, Cr, Zn, Fe) exposures.

Antioxidant systems are known to be sensitive to metal exposures and are suggested to use in predicting sublethal metal toxicity. In this study, several antioxidant enzymes, such as catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase (GST), glutathione peroxidase (GPX) and glutathione reductase (GR) were measured in the liver and kidney of Oreochromis niloticus exposed to sublethal concentrations of metals (Cd, Cu, Cr, Zn and Fe), using an acute (20 µM, 48 h) or subchronic (10 µM, 20 d) protocol. Beside the several increases of antioxidant enzyme activities, general inhibition was recorded after acute and chronic metal exposures. Results indicated that there were variations in responses of the enzymes to metal exposures, depending upon tissues, metals and exposure types. This study emphasized that the antioxidant enzymes are very sensitive to metals as their activities altered significantly, suggesting they could be helpful in predicting sublethal metal toxicity and useful as an early warning tool in natural monitoring studies.