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.     

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 Mg²⁺-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.     

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.     

Accumulation of Heavy Metals in Different Body Tissues of Atlantic Salmon,Salmo salar L., Exposed to a Model Mixture (Cu,Zn, Ni,Cr, Pb,Cd) and Singly to Nickel,Chromium, and Lead

One-year-old Atlantic salmon smolts were exposed for 2 weeks either to six priority heavy metal mixture or to Ni, Pb, and Cr singly at a concentration corresponding to Lithuanian inland water standards: Cu – 0.01, Zn – 0.1, Ni – 0.01, Cr – 0.01, Cd – 0.005 and Pb – 0.005 mg/L, respectively under semi-static conditions. The presence of metal mixture in the water only partly (by 50 %) affected the accumulation of single metals in body tissues (muscle, gills, liver and kidneys) probably due to the synergistic interactions among metals. Although metal concentrations increased in most cases, only Pb exceeded recommended level for human consumption (0.2 Pb mg/L) by 1.1-fold to 2.1-fold.     

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.     

Responses of the Antioxidant and Osmoregulation Systems of Fish Erythrocyte Following Copper Exposures in Differing Calcium Levels

Freshwater fish Oreochromis niloticus were exposed to Cu in differing Ca²⁺ levels (15, 30 and 90 mg/L), using acute (0.3 µM, 3 d) and chronic (0.03 µM, 30 d) exposure protocols and enzyme activities related to the antioxidant (catalase, CAT, EC 1.11.1.6; superoxide dismutase, SOD, EC 1.15.1.1; glutathione peroxidase, GPx, EC 1.11.1.9) and osmoregulation (Total, Na⁺/K⁺-ATPase, EC 3.6.3.9, Mg²⁺-ATPase, EC 3.6.3.2) systems in the erythrocytes were measured. Activities of antioxidant enzymes generally decreased significantly following either Ca²⁺ alone or Ca²⁺+Cu combinations in both acute and chronic exposures. Na⁺/K⁺-ATPase activity significantly decreased in chronic exposures, though there was no clear trend in acute exposures. Mg²⁺-ATPase activity increased significantly in acute exposures, but not in chronic ones. There were more significant alterations in acute exposure compared to chronic ones. There was no clear trend regarding Cu toxicity and its relationship with Ca²⁺, which may possibly be prompted by the compensatory mechanisms of the enzymes. It may be concluded that freshwater fish erythrocytes may face different degrees of more physiological stress from different waters.     

Effect of Chronic Sublethal Exposure of Major Heavy Metals on Filtration Rate, Sex Ratio, and Gonad Development of a Bivalve Species

The chronic toxic effects of major heavy metals including copper (Cu), zinc (Zn), lead (Pb), and cadmium (Cd) on the filtration rate (FR), sex ratio, and gonad development of immature blood clams, Tegillarca granosa, were investigated. The FRs were significantly inhibited by Cu, Pb and Cd, with rates generally decreasing with both increasing metal concentrations and exposure time. EC₅₀ values for FR after 28 days of exposure were 12.9, 12.7 and 14.4 μg/L for Cu, Pb and Cd, respectively. Zn exposure had no effect on FR. Sex ratios were significantly altered from controls in favor of an increased proportion of males at metal concentrations of ≥14.2, ≥86 and ≥110 μg/L for Cu, Pb and Cd, respectively; and at ≥1.68 mg/L for Zn. The gonado-somatic index was significantly reduced in clams at all metal exposures, except for the lowest concentration of Cu (7.1 μg/L).     

Lead-induced dysregulation of superoxide dismutases, catalase, glutathione peroxidase, and guanylate cyclase

Previous studies from this laboratory have demonstrated the presence of oxidative stress and its role in the pathogenesis of lead-induced hypertension. This study was designed to determine whether oxidative stress in animals with lead-induced hypertension is associated with dysregulation of the activities of the main antioxidant enzymes, namely superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX). In addition, we aimed to determine the effect of lead on the regulation of guanylate cyclase (GC) expression. Male Sprague-Dawley rats were randomly assigned to control and lead-exposed groups, and immunodetectable Cu/Zn SOD, Mn SOD, CAT, and GPX were determined by immunoblotting in the thoracic aorta. Additionally, the activities of these enzymes were measured in the renal cortex, medulla, and thoracic aorta. Furthermore, immunodetectable GC was determined in the thoracic aorta. In the thoracic aorta, lead exposure resulted in significant upregulation of aortic Cu/Zn SOD activity, while CAT and GPX activity and CuZn SOD, Mn SOD, and CAT protein abundance were unchanged. Conversely, GC protein abundance was decreased in thoracic aorta. In renal cortex and medulla, CAT and Cu/Zn SOD activities were increased, while GPX activity was unchanged. Lead-exposed animals exhibited upregulation of some antioxidant enzyme activities, most likely as a compensatory response to lead exposure. However, other enzymes did not compensate in the face of oxidative stress, suggestive of an antioxidant/oxidant imbalance. These findings, combined with decrease in aortic GC protein abundance, provide further evidence for dysregulation of antioxidant/oxidant balance and hypertension in this model.     

Accumulation and Elimination of Cadmium by the Nile Tilapia (Oreochromis niloticus) in differing Temperatures and Responses of Oxidative Stress Biomarkers

The aims of this study were to investigate the accumulation (15 days) and elimination (15 and 30 days) of cadmium (Cd) in the liver, gill, kidney and muscle of Oreochromis niloticus following exposures to different concentrations (1 and 2 mg/L) of Cd at different water temperatures (20, 25, 30 ^oC). Additionally, responses of oxidative stress biomarkers (superoxide dismutase, SOD; catalase CAT; glutathione peroxidase, GPx and malondialdehyde, MDA) of the liver were determined following Cd exposures. In accumulation period, Cd levels increased significantly in all the tissues at all temperatures and tissue accumulation order was kidney?>?liver?>?gill. All tissues, except the muscle, accumulated Cd in relation to exposure concentrations and water temperatures. There was no measurable level of Cd accumulation in the muscle, except in fish exposed to 2 mg Cd/L at 30 ^oC. Likewise, elimination of Cd from the tissues also increased in depends on periods and water temperatures. The order of Cd elimination from the tissues was gill?>?liver?>?kidney. The oxidative stress biomarkers also responded to both Cd exposure and temperature increases. The activities of antioxidant enzymes such as SOD, CAT, GPx and MDA levels in the liver increased in relation to increases in Cd concentrations and water temperatures.

     

Tissue-Specific Recovery of Oxidative and Antioxidant Effects of Chlorpyrifos in the Freshwater Crab,Barytelphusa guerini

Chlorpyrifos (CPF), an organophosphate widely applied in agriculture and aquaculture, induces oxidative stress due to free-radical generation and changes in the antioxidant defense system. The present study investigated the short-term effect of CPF exposure on the oxidative and antioxidant systems and their recovery responses in metabolically active tissues (gills, hepatopancreas [HP], and leg muscle) of freshwater crab Barytelphusa guerini. Crabs were exposed to a sublethal concentration of CPF (0.07 mg L^?1) for a total of 8 days (at intervals of 1, 2, 4, and 8 days) in clean water. The following oxidative stress markers were measured: acetylcholinesterase (AChE), butylcholinesterase (BChE), and ATPase; antioxidants i.e., superoxide dismutase (SOD), catalase, and glutathione reductase (GR), lipid peroxidation (LPO), conjugating enzyme glutathione S-transferase (GST), glutathione peroxidase (GPx), and lipid content. CPF exposure led to a significant decrease in the activity of oxidative stress markers as follows: AChE (84 %), BChE (46 %), and gills Na⁺/K⁺ ATPase (62 %). At the end of the recovery period, enzyme levels were recovered except in leg muscle. Total lipids and SOD decreased; CAT and LPO levels increased; and GPx, GR, and GST showed tissue-specific activities. Maximum recovery was observed in GPx followed by GR in HP tissue of crab. Nevertheless, these responses apparently grant successful adaptation for survival in a pesticide-extreme environment.     

Cadmium Accumulation in Gill,Liver, Kidney and Muscle Tissues of Common Carp,Cyprinus carpio,and Nile Tilapia,Oreochromis niloticus

Accumulation of cadmium in gill, liver, muscle and kidney tissues of Cyprinus carpio and Oreochromis niloticus were investigated in fish exposed to 0.5 ppm cadmium over 1, 15 and 30 days under controlled laboratory conditions. Tissue accumulation of the metal was measured using Atomic Absorption Spectrophotometric techniques. Cadmium accumulation in gill, liver, kidney and muscle, tissues of C. carpio and O. niloticus exposed to metal for 1, 15 and 30 days increased significantly compared with the control group (p < 0.05), except muscle tissue of O. niloticus. A general increase was observed in Cd accumulation with increasing exposure periods. Highest metal accumulation was observed in kidney followed by liver, gill and muscle tissues in both species. Liver accumulation of Cd was higher in C. carpio than O. niloticus, whereas kidney accumulation of the metal was higher in O. niloticus than C. carpio.     

Using the Comet Assay to Assess the Combined and Separate Genotoxic Effects of Cd and Zn in Eisenia andrei (Oligochaeta) at Different Temperatures

Using the comet assay, the genotoxicity of Cd, Zn and Cd/Zn mixtures in Eisenia andrei was assessed after 4 weeks of exposure at 15, 20 and 25°C. Relative to the controls, significant increases in TDNA% were observed in exposures to Cd alone at 500 and 1,000 mg/kg soil at both 20 and 25°C, while a general decrease occurred at 15°C. For Zn alone, a decreasing trend in TDNA% occurred at all three temperatures with increasing Zn concentration. For the Cd/Zn mixtures at 15°C, genotoxicity was reduced at all mixture concentrations relative to the control. At 20°C, the genotoxic response was similar to the control at all exposures. At 25°C, the response was elevated at the 50 + 50 and 250 + 250 mg/kg mixture concentrations. In the remaining treatments at 25°C, TDNA% was similar to the values in the respective control. The lack of consistently significant mixture genotoxicity may indicate antagonistic interactions between Cd and Zn in the mixtures. However, this was not conclusively determined because temperature alone had an inconsistent effect upon TDNA% readings in the control exposures.     

Heavy Metal Concentration in Largehead Hairtail (<Emphasis Type="Italic">Trichiurus lepturus</Emphasis> Linneaus, 1758) and Savalai Hairtail (<Emphasis Type="Italic">Lepturacanthus savala</Emphasis> (Cuvier, 1829)) Obtained from Karachi Fish Harbour,Pakistan

In this study, muscle samples gathered from Largehead hairtail (Trichiurus lepturus Linneaus, 1758) and Savali hairtail [Lepturacanthus savala (Cuvier, 1829)] from the Karachi Fish Harbour, Pakistan were analyzed to determine heavy metal concentrations (iron [Fe], zinc [Zn], copper [Cu], manganese [Mn], lead [Pb] and cadmium [Cd]) between January and December 2016. All samples were analyzed using the AAnalyst 700 Flame Atomic Absorption Spectrophotometer. It was observed that the average measured level of Fe, Zn, Cu, Mn, Pb and Cd in muscle were 77.72?±?47.84 µg/g, 20.34?±?8.49 µg/g, 2.23?±?1.16 µg/g, 0.57?±?0.36 µg/g, 0.20?±?0.16 µg/g and 0.42?±?0.19 µg/g for T. lepturus, respectively. Besides, the average level of the same metal concentrations in muscle for L. savala were 85.11?±?57.64 µg/g, 16.63?±?9.25 µg/g, 2.53?±?1.90 µg/g, 0.47?±?0.27 µg/g, 0.23?±?0.18 µg/g and 0.47?±?0.20 µg/g, respectively. The correlation between size groups and metal accumulation in muscle tissues were investigated for both fish. In terms of public risk assessment, the provisional tolerable weekly intake’s of various heavy metals were compared with the consumption of both fish. As a result of the analysis, Fe, Zn, Cu, Mn, Pb and Cd accumulations in muscle tissues of T. lepturus and L. savala collected from Karachi Fish Harbour Pakistan did not exceed limit values.     

Toxic Exposure of Songbirds to Lead in the Southeast Missouri Lead Mining District

Mining and smelting in the Southeast Missouri Lead Mining District has caused widespread contamination of soils with lead (Pb) and other metals. Soils from three study sites sampled in the district contained from approximately 1,000–3,200 mg Pb/kg. Analyses of earthworms [33–4,600 mg Pb/kg dry weight (dw)] collected in the district showed likely high Pb exposure of songbirds preying on soil organisms. Mean tissue Pb concentrations in songbirds collected from the contaminated sites were greater (p < 0.05) than those in songbirds from reference sites by factors of 8 in blood, 13 in liver, and 23 in kidney. Ranges of Pb concentrations in livers (mg Pb/kg dw) were as follows: northern cardinal (Cardinalis cardinalis) = 0.11–3.0 (reference) and 1.3–30 (contaminated) and American robin (Turdus migratorius) = 0.43–8.5 (reference) and 7.6–72 (contaminated). Of 34 adult and juvenile songbirds collected from contaminated sites, 11 (32 %) had hepatic Pb concentrations that were consistent with adverse physiological effects, 3 (9 %) with systemic toxic effects, and 4 (12 %) with life-threatening toxic effects. Acid-fast renal intranuclear inclusion bodies, which are indicative of Pb poisoning, were detected in kidneys of two robins that had the greatest renal Pb concentrations (952 and 1,030 mg/kg dw). Mean activity of the enzyme delta-aminolevulinic acid dehydratase (ALAD) in red blood cells, a well-established bioindicator of Pb poisoning in birds, was decreased by 58–82 % in songbirds from the mining sites. We conclude that habitats within the mining district with soil Pb concentrations of ≥1,000 mg Pb/kg are contaminated to the extent that they are exposing ground-feeding songbirds to toxic concentrations of Pb.     

Phytoremediation of Water Polluted by Thallium,Cadmium, Zinc,and Lead with the Use of Macrophyte Callitriche cophocarpa

The objective of the present work was to study the phytoremediation capacity of Callitriche cophocarpa concerning water contaminated with thallium (Tl), cadmium (Cd), zinc (Zn), and lead (Pb) derived from the natural environment. We found that after a 10-day incubation period, shoots of C. cophocarpa effectively biofiltrated the water so that it met (for Cd, Zn, and Pb) appropriate quality standards. The order of accumulation of the investigated elements by shoots (mg kg^?1 dry weight) were as follows: Zn (1120) < Tl (251) < Cd (71) < Pb (35). The order of bioconcentration factors were as follows: Cd (1177) < Tl (1043) < Zn (718) < Pb (597). According to Microtox bioassay, C. cophocarpa significantly eradicated polluted water toxicity. During the experiment, the physiological status of plants was monitored by taking measurements of photosystem II activity (maximum efficiency of PSII, photochemical fluorescence quenching, nonphotochemical fluorescence quenching, and quantum efficiency of PSII), photosynthetic pigment contents, and shoot morphology. Plants exposed to metallic pollution did not exhibit significant changes in their physiological status compared with the control. This work is potentially applicable to the future use of C. cophocarpa in the phytoremediation of polluted, natural watercourses.     

Concentrations of Cadmium,Copper, and Zinc in <Emphasis Type="Italic">Macrobrachium rosenbergii</Emphasis> (Giant Freshwater Prawn) from Natural Environment

This study analyzed the levels of cadmium (Cd), copper (Cu), and zinc (Zn) by the flame atomic absorption spectrophotometer (FAAS), in the muscle tissues, exoskeletons, and gills from freshwater prawn (Macrobrachium rosenbergii) (n?=?20) harvested from natural habitat in Kerang River, Malaysia on 25th November 2015. Significant increase of the metals level in muscle tissue and gill (r?>?0.70, p?<?0.05) were observed with increase in length except for Cu in gills. No relationship was found between metals level in exoskeleton and length. The concentrations of Cd, Cu and Zn were significantly higher (p?<?0.05) in males (muscle tissues and exoskeleton) except for Cd in exoskeleton. In gills, only Cu was significantly higher (p?<?0.05) in female than male. All samples contained metals below the permissible limit for human consumption (i.e., Cd?<?2.00 mg/kg; Cu?<?30.00 mg/kg; Zn?<?150 mg/kg). Annual metals monitoring in prawn and environmental samples is recommended to evaluate changes of metals bioaccumulation and cycling in the system, which is useful for resources management.     

Lead Concentrations in Sediments and Blue-Winged Teals (Anas discors) From El Palmar State Reserve, Yucatan, Mexico

Reserve regulations at El Palmar State Reserve, Yucatan, Mexico, prohibit the use of lead (Pb) shot, but hunters continue to use it, and no enforcement is implemented. Pb was quantified in sediments and in blue-winged teal Anas discors. No shot pellets were found in the sediment samples, nor were differences in sediment Pb concentrations observed within the reserve between popular hunting sites and those no longer used for hunting. However, there were differences between the hunting sites and sediments from an adjacent area where hunting is prohibited. Average Pb concentrations were highest at hunting entrances (15.69 ± 18.69 mg/kg) and lowest at decoy locations (5.24 ± 4.84 mg/kg). These averages are lower than the lowest effects level (31 mg/kg), although 10 samples exceeded this level. Pb-shot prevalence in gizzards was 4.88 % (n = 41). Pb levels exceeded 5.0 mg/kg dry weight in one or more of the tested tissues (liver, gizzard, and bone) in 14 (34.14 %; 7 female, 7 male; 11 adult, 3 juvenile) of the total birds. Bird weight, sex, and age had no effect on Pb concentration. Hunting using Pb shot in the reserve clearly affects Pb levels in sediments and in A. discors that winter there.     

Sublethal Zinc and Copper Exposure Affect Acetylcholinesterase Activity and Accumulation in Different Tissues of Leporinus obtusidens

In this study, we investigated zinc and copper effects on acetylcholinesterase (AChE, EC. 3.1.1.7) activity and metal accumulation in tissues of native fish Leporinus obtusidens (piava). Fish were exposed to 10 and 20 % of the LC₅₀ that corresponded at 2.28 and 4.57 mg/L (zinc) and 0.018 and 0.038 mg/L (copper) for 30 and 45 days. The AChE activity was evaluated in brain and white muscle of fish and metals accumulation was measured in kidney, liver, muscle and brain. Exposure to zinc and copper significantly increased AChE activity in both tissues and times tested, except for brain AChE activity at 2.28 mg/L of Zn (II) after 45 days where a reduction of 52.5 % was observed. Fish exposed to zinc showed accumulation of this metal in liver and kidney in both concentrations and times tested. A different result was obtained for copper: significant copper accumulation was obtained only in brain at both concentrations tested after 45 days of exposure. These results suggest that piavas exposed to zinc and copper showed changes in AChE activity and also demonstrate accumulation in some tissues. These results demonstrate that L. obtusidens could be a good bioindicator to evaluate water containing metals. The metal accumulation absence in muscle tissue is an indicative of low potential contamination by metals in this fish species.     

Effects of Paclobutrazol Exposure on Antioxidant Defense System in <Emphasis Type="Italic">Sebastiscus marmoratus</Emphasis>

This study was conducted to detect the effects of paclobutrazol (PBZ) at environmental concentration on the antioxidant defense system in Sebastiscus marmoratus. Fish were exposed to concentrations of PBZ (10, 100, 1,000 ng/L) for 50 days. The results showed: (1) The glutathione contents in the liver and brain were significantly decreased in a dose-dependent manner. (2) The activities of glutathione S-transferases (GST) and catalase in liver and brain were inhibited as the increase of PBZ concentration. A highest 2.16-fold (p = 0.05) and 11.54-fold (p < 0.001) reduction of GST activity in the liver and brain respectively was observed in 1,000 μg/L group. (3) The activities of glutathione peroxidase in liver were inhibited. These results suggest that the exposure of PBZ would influence the antioxidant ability of S. marmoratus.     

Glutathione, Glutathione-Related Enzymes, and Catalase Activities in the Earthworm Eisenia fetida andrei

The aim of this work was to provide basic data on the antioxidant defences in the annelid Eisenia fetida andrei (E. f. a.). Methods for measurement of three antioxidant enzymes—catalase (CAT), glutathione peroxidase (GPX), and glutathione reductase (GR)—and of glutathione-S-transferase (GST) were optimized. GPX activity differed according to the substrate used: cumene hydroperoxide (CUOOH) or hydrogen peroxide (H₂O₂). The effects on the enzyme activities of storage up to 2 months at −80°C, −20°C, and +4°C were evaluated. The subcellular distribution (in cytosol, mitochondrial, and microsomal fractions) was examined. The properties and subcellular distribution of the enzymes and glutathione were also characterized in dissected tissues and body fluids. The GR activity decreased at −80°C and was the only one not stable at this temperature. The four enzymes were localized mainly in the cytosolic fraction. CAT distribution was unusual as it was not associated with peroxisomes, its properties being consistent with a catalase-peroxidase, rather than a true catalase. However, this result could also be an artifact linked to the use of an inappropriate method to obtain the fractions. Our observations indicate the presence of a distinct cytosolic selenium-dependent GPX (Se-GPX), and of a possible microsomal Se-GPX. A strong non–Se-GPX activity was measured in the CF and CL, which could be linked to the peroxidase activity of fetidins secreted by coelomocytes and with the ROS production of these cells. This study seems to indicate that E. f. a. is well equipped for the metabolism of electrophilic and pro-oxidants through glutathione. Received: 18 February 1998/Accepted: 11 June 1998