Zn In Gills Research Articles

Monitoring changes in accumulation of heavy metals in the Egyptian Delta region in 2010 and 2021, using the crayfish Procambarus clarkii (Girard, 1852) (Decapoda, Astacidea) as a bio-indicator

Abstract Accumulation of heavy metals in tissues of the crayfish Procambarus clarkii and in water were evaluated in areas located in the Egyptian Delta (Gharbiya, Kafr El-Shaikh, and Menofiya) in 2010 and 2021. Statistics showed that in 2010 the highest concentration of heavy metals in the digestive gland and in muscles was Zn, both in Gharbiya and Menofiya, while Fe was the highest accumulated in the digestive gland, and Pb was the highest in muscles of samples from Kafr El-Shaikh. The results showed that heavy metal loads decreased in Kafr El-Shaikh in 2021, whereas Fe increased significantly () in Gharbiya and Menofiya (41.44 ± 2.32, 47.25 ± 2.64 μg/g). Accumulation of Cd and Zn in gills and muscles decreased in all areas from 2010 to 2021, while a significant increase () was shown in Fe and Cu in 2021. All heavy metals significantly decreased () in waters of the studied areas from 2010 to 2021.

Accumulation of 25 elements in gills, liver, gonads, and muscle of European chub (Squalius cephalus), Cactus roach (Rutilus virgo), and pikeperch (Sander lucioperca) from Zlatar reservoir (Serbia).

Accumulation of Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Se, Si, Sr, and Zn was analyzed in gills, liver, gonads, and muscle of European chub (Squalius cephalus), Cactus roach (Rutilus virgo), and pikeperch (Sander lucioperca) from Zlatar reservoir (Serbia) using inductively coupled plasma optical emission spectrometry (ICP-OES). The highest concentrations of Cu in liver as well as Ba, Ca, Fe, Mn, Na, P, and Sr in gills were detected in all fish species, while the lowest concentrations of Cu, Fe, Mn, Na, and Zn were detected in muscle. Pikeperch had significantly lower concentrations of Ba in all tissues compared to the other species, as well as Fe, P, and Sr in muscle, K, Mg, Mn, Sr, and Zn in gills, and Fe in gonads. European chub had significantly higher concentrations of Ca, Cu, and Zn in muscle, Cu in liver, and Cr and Cu in gonads compared to Cactus roach and pikeperch. Cd concentration in one individual of Cactus roach exceeded the maximum allowed concentration. The muscle was exposed to the lowest pressure of metal pollution in all species, and European chub accumulated more metals compared to the other species. There is no significant health risk due to consumption of investigated species. A major hazard index (HI) contributor in all species was Hg. According to the target carcinogenic risk factor (TR), target hazard quotient (THQ), and HI, men are under lower health risk compared to the women. The TR and THQ for As, Cr, Cu, Fe, Mn, Ni, and Zn as well as HI values were higher for European chub compared to the other species. On the other hand, THQ for Hg was highest for pikeperch.

Trophic transfer potential of nTiO2, nZnO, and triclosan in an algae-algae eating fish food chain.

Little is known about the trophic transfer of nanoparticles and personal care products via dietary exposure in an algae-algae eating fish food chain. The bioaccumulation of nano-TiO2 (P25 - nTiO2), nano-ZnO (nZnO), and triclosan (TCS) in eight different combinations were explored in this study through algae, Asterococcus superbus, to fish, Gyrinocheilus aymonieri. Results found the bioaccumulation of TCS changed with algal biomass, while the bioaccumulation of Ti and Zn varied with the amount of lipids and proteins in algal cells. In algae, Ti was in the form of nTiO2 and Zn in the form of zinc ion. Due to dietary exposure, Ti and Zn quantity in fish was closely related to that in algae. The quantity of Ti and Zn in algae and fish exposed to the interaction of nTiO2 * nZnO* TCS was higher than that in other treatments. The uptake of Ti and Zn in algae exposed to the interaction of nTiO2 * nZnO had been inhibited, and the corresponding fish also had less Ti and Zn in their tissues. nTiO2-containing treatments had higher Ti proportion in muscle than gill in fish. Treatment nZnO had the most Zn in gill, whereas nZnO * TCS-containing treatments had higher Zn proportion in gut than other tissues. No observation of TCS in fish in all treatments suggested the removal and metabolism of TCS might be induced by tissue recovery and acclimation. This is the first report on trophic transfer of mixed nanoparticles and personal care product in an algae-algae eating fish two-stage food chain.

Age-specific accumulation of toxic metal(loid)s in northern pike (Esox lucius) juveniles.

Northern pike specimens of 0+, 1+, and 2+ age classes were collected in June 2013 from the Vizelj channel near Belgrade (Serbia). Inductively coupled plasma optical spectrometry (ICP-OES) and atomic absorption spectrometer SpectrAA 220 were used for analyzing concentrations of As, Cr, Cd, Co, Cu, Fe, Sr, Pb, and Zn, as well as Hg in muscle, gills, and liver. Metal pollution index (MPI) was calculated. Concentrations of As, Cd, Co, and Pb were below the limit of detection. Concentrations of Cu, Hg, and Zn in muscle did not exceed the maximum allowed concentrations. The gills were tissue which was most affected by pollution. The highest concentrations of Fe in muscle, Cr and Fe in gills, and Hg, Sr, and Zn in liver were recorded in 0+ individuals, as well as Zn in gills of 2+ individuals. On contrary, the lowest concentrations were recorded for Zn in gills of 0+ individuals, Hg in gills of 1+ individuals, and Fe in muscle, Cr and Sr in gills, and Zn in liver of 2+ individuals. Regarding age classes, 2+ juveniles had the highest MPI values for all tissues. Correlations between the metal(loid) accumulation and fish condition were not significant, as well as between fish length and weight and Cu and Hg in muscle, Cu, Hg, and Sr in gills, and Cu, Cr, and Fe in liver. Results indicated that young individuals were more sensitive to pollution, but older fish showed higher overall bioaccumulation of toxic elements analyzed in this study.

Toxicity of representative mixture of five rare earth elements in juvenile rainbow trout (Oncorhynchus mykiss) juveniles

Rare earth elements (REEs) are contaminants of increasing interest due to intense mining activities for commercial purposes and ultimately released in the environment. We exposed juvenile rainbow trout (Oncorhynchus mykiss) to a representative mixture of the five most abundant REEs for 96 h at concentrations similar found in lakes contaminated by mining activities at 0.1, 1, 10, and 100X whereas the 1x mixture contained cerium (Ce, 280 μg/L), lanthanum (La, 140 μg/L), neodymium (Nd, 120 μg/L), praseodymium (Pr, 28 μg/L), and samarium (Sm, 23 μg/L). We investigated the expression of 14 genes involved in oxidative stress, DNA repair, tissue growth/proliferation, protein chaperoning, xenobiotic biotransformation, and ammonia metabolism in the liver. In addition, DNA damage, oxidative stress (lipid peroxidation or LPO), inflammation (cyclooxygenase or COX activity), detoxification mechanisms (glutathione-S-transferase activity or GST), and labile zinc were determined in gills. The data revealed that genes involved in oxidative stress-catalase (cat), heat shock proteins 70 (hsp70), and glutamate dehydrogenase (glud) were upregulated while glutathione S-transferase (gst) and metallothionein (mt) gene expressions were downregulated. The mixture was genotoxic and increased labile Zn in gills of exposed trout. These changes occurred at concentrations 600 times lower than the LC50 for this mixture indicating effects below the 1X concentration. Based on principal component analysis and concentration-dependent reponses, the following sublethal effects were considered the most important/significant: DNA strand breaks (genotoxicity), labile Zn, cat, gst, hsp70, sparc, mt, and glud. These effects of fish juveniles are likely to occur in environments under the influence of mining activities.

Trace metals in six fish by-products of two farmed fishes, the gilthead sea bream (Sparus aurata) and the meager (Argyrosomus regius): Interactions with the environment and feed

For the large producers of farmed fish, the utilization of fish by-products as ingredients of food is important and thus their characterization, in terms of chemical composition and safety, becomes necessary. In this study, eleven trace metal concentrations in by-products (head, gills, guts, trimmings, bones and skin) of two Mediterranean farmed fishes, the gilthead sea bream (Sparus aurata) and the meager (Argyrosomus regius) were determined by ICP-MS. According to overall concentrations, the sequence of trace metal levels in decreasing order was Fe > Zn > Mn > Cu > As > Cr > Pb > Ni > Cd > V>Co. Higher median concentrations (μg g−1 d.w.) of As were determined in bones and guts (2.16 and 2.04), Cd, Co, Cu, Pb in guts (0.175, 0.058, 16.3, 0.381), Cr in skin and bones (1.51 and 1.45), Ni in guts and skin (0.231, 0,218), Fe and Mn in gills (50.1, 16.8) and V in trimmings (0.052). Trace metal levels determined in fish feed were considerably lower compared to EC limits (Directive 2002/32/EC). The highest bioconcentration factor (BCF) values were calculated for Cd, Ni, Pb in muscle, for Fe, Mn, Zn in gills, for Cd, Co, Cu, Zn in guts and for Cr in bones. Exploitation of fish by-products as additives in food industry appears feasible, based on the concentrations of metals examined.

Metal bioaccumulation, oxidative stress and antioxidant responses in oysters Crassostrea gasar transplanted to an estuary in southern Brazil

The present study assessed the spatial and temporal variations on metal bioaccumulation and biochemical biomarker responses in oysters Crassostrea gasar transplanted to two different sites (S1 and S2) at the Laguna Estuarine System (LES), southern Brazil, over a 45-days period. A multi-biomarker approach was used, including the evaluation of lipid peroxidation (MDA) levels, and antioxidant defense enzymes (CAT, GPx, GR and G6PDH) and phase II biotransformation enzyme (GST) in the gills and digestive gland of oysters in combination with the quantification of Al, Cd, Cu, Pb, Fe, Ni and Zn in both tissues. The exposed oysters bioaccumulated metals, especially Al, Cd and Zn in gills and digestive gland, with most prominent biomarker responses in the gills. Results showed that GPx, GR and G6PDH enzymes offered an increased and coordinated response possibly against metal (Zn, Ni, Cd and Cu) contamination in gills. GST was inversely correlated to Cd levels, being its activity significantly lowered over the 45-d exposure periods at S2. On contrary, in digestive gland GST was slightly positively correlated to Cd, revealing a compensatory mechanism between tissues to protect oysters' cells against oxidative damages, since MDA levels also decreased. CAT also appeared to be involved in the cellular protection against oxidative stress, being increased in gills. However, CAT was negatively correlated to Al levels, which might suggest a possible inhibitory effect of this metal in the gills of C. gasar. Differences between tissues were evident by the Integrative Biomarker Responses version 2 (IBRv2) indexes, which showed different pattern between tissues when studying the sites and exposure periods separately. This study provided evidence for the effectiveness of using a multi-biomarker approach in oyster C. gasar to monitor estuarine metal pollution.

Distribution and speciation of zinc in the gills of rainbow trout (Oncorhynchus mykiss) during acute waterborne zinc exposure: Interactions with cadmium or copper

We utilized micro X-ray fluorescence imaging (μ-XFI) and micro X-ray absorption near-edge spectroscopy (μ-XANES), which are both synchrotron-based techniques to investigate Zn distribution profile, its co-localization patterns with Ca, S, and Fe and speciation in the gills of rainbow trout (RBT). Fish (~100 g) were exposed to acutely toxic levels of waterborne Zn alone and in combination with waterborne Cd or Cu for 24 h (each at 1 × 96 h LC50). Gill sections were prepared and analyzed at the VESPERS beamline of the Canadian Light Source. The primary lamellae of the fish gill were found to be the primary area of Zn accumulation. These regions also correspond to the zones of mitochondria rich cells localization in fish gills, supporting the putative roles of these cells in metal uptake. Zn was also found to predominantly co-localize with Ca and S, but not with Fe, indicating the roles of Ca and S in intracellular Zn handling. Zn distribution in the gill was markedly reduced during co-exposure to Cd, but not to Cu, suggesting a competitive interaction between Zn and Cd for uptake. The speciation of Zn in the gill was dominated by Zn-phosphate, Zn-histidine and Zn-cysteine species; however, the interactions of Zn with Cd or Cu resulted in the loss of Zn-cysteine. Overall, our findings provide important novel insights into the interactions of Zn, Cd and Cu in the fish gill, which may ultimately help to explain the mechanisms underlying the acute toxicity of these metals in binary mixture to fish.

Fish as a bioindicator of heavy metals pollution in aquatic ecosystem of Pluszne Lake, Poland, and risk assessment for consumer's health

Heavy metals content (Zn, Cu and Hg) were measured in gills, liver, gonads and muscles of perch, Perca fluviatilis (L.) and roach, Rutilus rutilus (L.) from Lake Pluszne (north-eastern Poland). Correlations between heavy metals levels and total length, weight, HSI, GSI and FCF were examined. As expected, muscles contained the significantly highest values of Hg (P ≤ .05). The concentrations of Zn were significantly higher in gills of roach and gonads of perch (P ≤ .05), while the liver of fish accumulated significantly more Cu than other organs (P ≤ .05). In all organs of perch the higher content of mercury was found (P ≤ .05). The value of Zn and Cu was highest in organs of roach (P ≤ .05) (with the exception of Zn in muscles P > .05). Sequence of metals in both species was Zn > Cu > Hg. Only in muscle tissue, Hg was significantly positive correlated with weight of roach (r = 0.811, P = .045) and perch (r = 0.652, P = .041), and total length of roach (r = 0.806, P = .005). A positive relationship was also observed between Zn concentration in gills of perch and their weight (r = 0.634, P = .049). In contrary, Zn in gills of roach decreased with weight (r = −0.693, P = .026)) and length (r = −0.668, P = .035). Cu concentration in liver of perch was statistically positively correlated with HSI (r = 0.717, P = .020), whereas Hg content in muscle tissue of roach with FCF (r = 0.643, P = .045). There was negative relationship between Hg in perch gonads and GSI (r = −0.808, P = .005). Metal pollution index (MPI) in gills, liver, gonads and muscles of roach was 7.68, 7.24, 6.77 and 3.13, respectively, whereas in these organs of perch was 3.25 (gills), 4.75 (liver), 5.84 (gonads) and 4.44 (muscles), therefore the contamination of each tissue ranged from very low contamination to low contamination. The concentration of mercury was lower than the maximum acceptable limit estimated by the Commission Regulation (EC) No 629/2008 of 2 July 2008. The values of HI and THQ were below 1, which means that consumption of these fish is not hazardous to the consumer.

Toxic element determination in fish from Paraná River Delta (Argentina) by neutron activation analysis: Tissue distribution and accumulation and health risk assessment by direct consumption

The concentrations of As, Co, Fe, Hg, and Zn were determined by INAA in muscle, gills, liver and scale of silversides (Odontesthes bonariensis) and sardine (Lycengraulis grossidens) from Paraná River Delta (Argentina) and the human health risk related to the consumption of muscle was evaluated. Detection limits were among 0.001 and 0.3mg/kg, the RSD values were below 12% and certified reference material showing good accuracy. Considering all tissues and species, elements concentrations (mg/kg, ww) were: As: (0.35–1.30), Co (0.008–0.29), Fe (2.22–369.5), Hg (nd–1.11) and Zn (5.83–187.6). Most of the trace elements tended to be higher in L. grossidens, except for Co, Fe and Zn in gills and Hg in liver. Elements accumulation order for both species was Zn>Fe>As>Hg>Co in muscle and scale and Fe>Zn>As>Hg>Co for gills and liver. The highest concentrations of As and Co were found in liver, Hg in muscle and liver, Fe and Zn in liver and scale for sardine, and gills and liver for silversides. The levels of Hg in muscle were above the maximum recommended established by national or international guidelines. The THQ of each metal and the total THQ due to fish consumption were less than 1 for general population, suggesting that people would not experience significant health risks. However, for fishermen group, the total THQ was higher than 1, indicating the potential health risks of chronic exposure to contaminants.

The impact of zinc oxide nanoparticles in freshwater mussels exposed to municipal effluents

Zinc oxide nanoparticles (nano-ZnO) are used in the production of transparent sunscreens and cosmetics, which are released into the environment through municipal effluents. The purpose of this study was to examine the toxicity of nano-ZnO to freshwater mussels (Elliptio complanata) in the presence of municipal effluents. Mussels were exposed for 21 days at 15 o C to 1 and 10 µg/L nanoZnO, and ZnCl2 in the presence of a physico-chemically treated municipal effluent (3 and 10 % v/v). After the exposure period and a 24 h depuration step, mussels were analyzed for free Zn in gills, metallothioneins (MT), oxidative stress (production of malondialdehyde (MDA) during lipid peroxidation), gonad alkali-labile phosphate (ALP) levels and genotoxicity. Gill MT levels were increased at 10 µg/L nano-ZnO and ZnCl2 and in the presence of the municipal effluent. MT levels were positively correlated with free Zn in gills and negatively correlated with MDA levels, indicating its involvement in the prevention of oxidative stress. However, MDA levels were significantly related to DNA damage in gills, indicating that MT induction did not prevent oxidative-mediated damage in cells. Gonad ALP levels were increased by exposure to ZnCl2 and to the highest concentration of municipal effluent. DNA strand breaks were increased in mussels treated to nano-ZnO indepentely of municipal effluent. Multivariate discriminant function analysis revealed that control mussels differed from mussels exposed to the municipal effluent and from those exposed to nano-ZnO or ZnCl2 alone. When the municipal effluent was added, changes in MDA, MT and labile Zn were produced and formed another cluster, suggesting a change in the toxicity of the municipal effluent in the presence of nano-ZnO.

Effects of exposure to zinc oxide nanoparticles in freshwater mussels in the presence of municipal effluents

Zinc oxide (nano-ZnO) nanoparticles are used in the production of transparent sunscreens and cosmetics, which are released into surface waters and municipal wastewater effluent. The purpose of this study was to examine the toxicity of nano-ZnO in the presence of municipal effluents to freshwater mussels Elliptio complanata. Mussels were exposed for 21 days at 15 o C to nano-ZnO and ZnCl2 in the presence of 10 % dilution of primary-treated municipal effluent. After the exposure period and 24-h depuration step, mussels were analyzed for total Zn in gills and digestive gland, free Zn, metallothioneins (MT), oxidative stress (glutathione S-transferase and LPO), endoplasmic reticulum stress (heat shock proteins and protein ubiquitination) and genotoxicity. The data revealed that although total Zn loadings did not change with these treatments, Zn levels in digestive gland were elevated in mussels exposed to nano-ZnO but not with ZnCl2 in the presence of municipal effluent. Free Zn levels in the gills were elevated in mussels exposed to the municipal effluent, but decreased in mussels exposed to nano-ZnO. MT in digestive gland showed a similar pattern and was negatively associated with free and total Zn. GST activity was significantly reduced by both nano-ZnO and municipal effluent and was negatively correlated with MT levels, suggesting the involvement of MT in the sequestration of reactive oxygen species. Discriminant function analysis showed that the municipal effluent related effects differed from the unexposed mussels and nano-ZnO exposed mussels in terms of the following responses: free Zn in gills and digestive gland and GST activity. Nano-ZnO related effects also involved GST activity, MT and protein ubiquitination, which suggests a combination of oxidative stress and reticulum endoplasmic stress. In respect with oxidative stress, the oxidative properties of nano-ZnO and ZnCl2 are dampened in the presence of the municipal effluent.

Seasonal determination of heavy metals in muscle, gill and liver tissues of Nile tilapia,Oreochromis niloticus(Linnaeus, 1758) from the tributary of the Ganga River, India

Aquatic biota is contaminated with heavy metals as a result of anthropogenic activities and industrialization. Heavy metals, that is copper (Cu), chromium (Cr), lead (Pb) and zinc (Zn), were analysed in Oreochromis niloticus collected from the Gomti River at Lucknow and Jaunpur sites, India, from 2011 to 2012. Accumulation of heavy metals was estimated in different tissues of tilapia. At both study sites (Lucknow and Jaunpur), metal accumulation in different tissues of this fish was found to be in the following order: Zn > Pb > Cr > Cu in muscles, Zn > Pb > Cr > Cu in gills and Pb > Cr > Cu > Zn in liver. However, it was established that the level of heavy metals in all fish organs at the Lucknow site (except Pb and Zn in gills) was higher. The determined bioconcentration factor of heavy metals in different fish organs at the Lucknow site was as follows: Cu (26.5), Cr (38.33), Pb (52.33), Zn (23.41) in muscles, Cu (36.5), Cr (56.33), Pb (95.66) and Zn (31.66) in gills and Cu (381.50), Cr (367.33), Pb (410...

Concentrations of 17 elements in muscle, gills, liver and gonads of five economically important fish species from the Danube River

The Danube River in the vicinity of the city of Belgrade receives large amounts of untreated or poorly treated communal and industrial waste waters. The aim of this study was to assess elemental accumulation patterns in a number of economically important fish species in this area that belong to different trophic levels. Concentrations of 17 elements (Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Li, Mn, Mo, Ni, Pb, Se, Sr and Zn) were assessed in liver, muscle, gills and gonads of silver carp (Hypophthalmichthys molitrix ), freshwater bream (Abramis brama ), white bream (Blicca bjoerkna ), common carp (Cyprinus carpio ) and wels catfish (Silurus glanis ) from the Danube River in Serbia by the use of ICP-OES. Silver carp specimens were differentiated from the other four species by high concentrations of Al and Fe in the liver. Common carp specimens were differentiated by high concentrations of Zn in gills, muscle and liver. Distribution of elements among different tissues had a consistent pattern among the species. Concentrations of Pb, Cd, As, Zn, Cu and Fe in muscle were at acceptable levels for human consumption, while concentrations of Fe and Zn were above maximum acceptable concentrations in liver and gonads.

AN ENRICHED STABLE-ISOTOPE APPROACH TO DETERMINE THE GILL–ZINC BINDING PROPERTIES OF JUVENILE RAINBOW TROUT (ONCORHYNCHUS MYKISS) DURING ACUTE ZINC EXPOSURES IN HARD AND SOFT WATERS

The objective of the present study was to employ an enriched stable-isotope approach to characterize Zn uptake in the gills of rainbow trout (Oncorhynchus mykiss) during acute Zn exposures in hard water (approximately 140 mg/L as CaCO3) and soft water (approximately 30 mg/L as CaCO3). Juvenile rainbow trout were acclimated to the test hardnesses and then exposed for up to 72 h in static exposures to a range of Zn concentrations in hard water (0-1000 microg/L) and soft water (0-250 microg/L). To facilitate detection of new gill Zn from endogenous gill Zn, the exposure media was significantly enriched with 67Zn stable isotope (89.60% vs. 4.1% natural abundance). Additionally, acute Zn toxicity thresholds (96-h median lethal concentration [LC50]) were determined experimentally through traditional, flow-through toxicity tests in hard water (580 microg/L) and soft water (110 microg/L). Following short-term (< or =3 h) exposures, significant differences in gill accumulation of Zn between hard and soft water treatments were observed at the three common concentrations (75, 150, and 250 microg/L), with soft water gills accumulating more Zn than hard water gills. Short-term gill Zn accumulation at hard and soft water LCS0s (45-min median lethal accumulation) was similar (0.27 and 0.20 microg/g wet wt, respectively). Finally, comparison of experimental gill Zn accumulation, with accumulation predicted by the biotic ligand model, demonstrated that model output reflected short-term (<1 h) experimental gill Zn accumulation and predicted observed differences in accumulation between hard and soft water rainbow trout gills. Our results indicate that measurable differences exist in short-term gill Zn accumulation following acclimation and exposure in different water hardnesses and that short-term Zn accumulation appears to be predictive of Zn acute toxicity thresholds (96-h LC50s).

Bioaccumulation and subcellular partitioning of zinc in rainbow trout ( Oncorhynchus mykiss): Cross-talk between waterborne and dietary uptake

Zinc homeostasis was studied at the tissue and gill subcellular levels in rainbow trout ( Oncorhynchus mykiss) following waterborne and dietary exposures, singly and in combination. Juvenile rainbow trout were exposed to 150 or 600 μg l −1 waterborne Zn, 1500 or 4500 μg g −1 dietary Zn, and a combination of 150 μg l −1 waterborne and 1500 μg g −1 dietary Zn for 40 days. Accumulation of Zn in tissues and gill subcellular fractions was measured. At the tissue level, the carcass acted as the main Zn depot containing 84–90% of whole body Zn burden whereas the gill held 4–6%. At the subcellular level, the majority of gill Zn was bioavailable with the estimated metabolically active pool being 81–90%. Interestingly, the nuclei-cellular debris fraction bound the highest amount (40%) of the gill Zn burden. There was low partitioning of Zn into the detoxified pool (10–19%) suggesting that sequestration and chelation are not major mechanisms of cellular Zn homeostasis in rainbow trout. Further, the subcellular partitioning of Zn did not conform to the spill-over model of metal toxicity because Zn binding was indiscriminate irrespective of exposure concentration and duration. The contribution of the branchial and gastrointestinal uptake pathways to Zn accumulation depended on the tissue. Specifically, in plasma, blood cells, and gill, uptake from water was dominant whereas both pathways appeared to contribute equally to Zn accumulation in the carcass. Subcellularly, additive uptake from the two pathways was observed in the heat-stable proteins (HSP) fraction. Toxicologically, Zn exposure caused minimal adverse effects manifested by a transitory inhibition of protein synthesis in gills in the waterborne exposure. Overall, subcellular fractionation appears to have value in the quest for a better understanding of Zn homeostasis and interactions between branchial and gastrointestinal uptake pathways.

Changes in plasma electrolytes and Gill Histopathology in Wild Liza saliens from the Esmoriz-Paramos Coastal Lagoon, Portugal

The Esmoriz-Paramos is a lagoon of great ecological significance located on the Northwest coast of Portugal. The quality of water and sediment within this ecosystem has been gradually degraded due to the discharges of mostly untreated industrial waste and domestic sewage. Contaminants include heavy metals that can be taken up by fish from water, food, sediments, and suspended particulate material. Fish inhabiting polluted water bodies tend to accumulate many chemicals in high concentrations, even when the environmental contamination levels are low (Colombo et al. 1995). The leaping grey mullet (Liza saliens) is one of a few dominant species living in this environment. This species may contact xenobiotics in the water column or, when feeding, in the sediments. Previous studies have analyzed heavy metal concentrations in the water and sediments of this lagoon, and evaluated their bioaccumulation in L. saliens (Fernandes et al. 2007a, b). According to these studies, the seasonal range of metal concentrations in surface water was 0.003–0.031 mg Cu L, 0.006–0.811 mg Zn L and 0.01–0.026 mg Pb L, all mainly found in particulate matter. The main metals found in sediments were Cu, Zn and Pb, respectively 83, 241 and 87 mg kgd.w. The Cu and Zn concentrations in L. saliens liver were 262 and 89 mg kgd.w. and below the detection limit for Pb (0.073 ppm), whereas these concentrations in the gill were 9 mg Cu kg d.w.; 114 mg Zn kg d.w. and 0.6 mg Pb kg d.w. Also, significant age-related increase of metal concentrations in tissues, were noted, for Zn in gill and for Cu in liver and gill (Fernandes et al. 2007a). The gill is particularly sensitive to physical and chemical changes in the aquatic environment and it is the main target organ in fish for toxic waterborne heavy metals (McDonald and Wood 1993). Effects of metals on ionoregulatory gill functions have been well demonstrated, including regulation of plasma electrolytes (Mazon et al. 2002; Grosell et al. 2003; Martinez et al. 2004). The histological effects of metals on fish gill have also been studied in several fish species (Arellano et al. 1999; De Boeck et al. 2001). The mechanisms of acute Cu toxicity include the osmoregulatory disturbances involving Na, Cl and K uptake by the gill (Mazon et al. 2002; Grosell et al. 2003). Although the mechanisms of heavy metals toxicity are well known in acute exposure, the process may differ in chronic exposure (Handy 2003). The objectives of this study were to evaluate the plasma electrolyte concentrations of wild Liza saliens from the Esmoriz-Paramos lagoon and to assess the osmoregulatory responses and branchial histopathological changes related to chronic heavy metal exposure in this habitat.

Toxicity of single walled carbon nanotubes to rainbow trout, ( Oncorhynchus mykiss): Respiratory toxicity, organ pathologies, and other physiological effects

Mammalian studies have raised concerns about the toxicity of carbon nanotubes (CNTs), but there is very limited data on ecotoxicity to aquatic life. We describe the first detailed report on the toxicity of single walled carbon nanotubes (SWCNT) to rainbow trout, using a body systems approach. Stock solutions of dispersed SWCNT were prepared using a combination of solvent (sodium dodecyl sulphate, SDS) and sonication. A semi-static test system was used to expose rainbow trout to either a freshwater control, solvent control, 0.1, 0.25 or 0.5 mg l −1 SWCNT for up to 10 days. SWCNT exposure caused a dose-dependent rise in ventilation rate, gill pathologies (oedema, altered mucocytes, hyperplasia), and mucus secretion with SWCNT precipitation on the gill mucus. No major haematological or blood disturbances were observed in terms of red and white blood cell counts, haematocrits, whole blood haemoglobin, and plasma Na + or K +. Tissue metal levels (Na +, K +, Ca 2+, Cu, Zn and Co) were generally unaffected. However some dose-dependent changes in brain and gill Zn or Cu were observed (but not tissue Ca 2+), that were also partly attributed to the solvent. SWCNT exposure caused statistically significant increases in Na +K +-ATPase activity in the gills and intestine, but not in the brain. Thiobarbituric acid reactive substances (TBARS) showed dose-dependent and statistically significant decreases especially in the gill, brain and liver during SWCNT exposure compared to controls. SWCNT exposure caused statistically significant increases in the total glutathione levels in the gills (28%) and livers (18%), compared to the solvent control. Total glutathione in the brain and intestine remained stable in all treatments. Pathologies in the brain included possible aneurisms or swellings on the ventral surface of the cerebellum. Liver cells exposed to SWCNT showed condensed nuclear bodies (apoptotic bodies) and cells in abnormal nuclear division. Overt fatty change or wide spread lipidosis was absent in the liver. Fish ingested water containing SWCNT during exposure (presumably stress-induced drinking) which resulted in precipitated SWCNT in the gut lumen and intestinal pathology. Aggressive behaviour and fin nipping caused some mortalities at the end of the experiment, which may be associated with the gill irritation and brain injury, although the solvent may also partly contributed to aggression. Overall we conclude that SWCNTs are a respiratory toxicant in trout, the fish are able to manage oxidative stress and osmoregulatory disturbances, but other cellular pathologies raise concerns about cell cycle defects, neurotoxicity, and as yet unidentified blood borne factors that possibly mediate systemic pathologies.

Antioxidative stress proteins and their gene expression in brown trout ( Salmo trutta) from three rivers with different heavy metal levels

Three populations of brown trout ( Salmo trutta) exposed to different metal levels in their natural environments, were studied with respect to antioxidants metallothionein (MT), superoxide dismutase (SOD) and catalase (CAT) as well as for corresponding mRNA levels. In addition, mRNA levels were studied for glutathione peroxidase (GPx) and glutathione reductase (GR). The Cd/Zn-exposed trout (Naustebekken River) had higher accumulated levels of Cd, Cu and Zn in gills, and higher levels of MT (both protein and mRNA) in liver and kidney as well as in gills compared to the Cu-exposed trout (Rugla River) and trout from an uncontaminated reference river (Stribekken River). Less MT found in the Cu-exposed trout may increase susceptibility to oxidative stress, but no higher levels of antioxidant mRNAs were found in gills of these trouts. The data indicated that chronic exposures of brown trout to Cd, Zn and/or Cu did not involve maintenance of high activities of SOD and CAT enzymes in gills, although SOD mRNA levels were higher in the Cd/Zn-exposed trout. In livers, mRNA levels of SOD, CAT and GPx were higher in the metal-exposed trout, but in the case of GR this was only seen in kidneys of Cd/Zn-exposed trout. However, both metal-exposed groups had higher activities of SOD enzyme in liver compared to the unexposed reference trout, and CAT activity was found to be higher in kidneys of Cu-exposed trout. The Cu-exposed trout did not seem to rely on MT production to avoid Cu toxicity in gills, but rather by keeping the Cu uptake at a low level. A coordinated expression of different stress genes may also be important in chronic metal exposure. It may be concluded that the observed metal effects relies on acclimation rather than on genetic adaptation in the metal exposed populations.

Sub-cellular partitioning of metals (Cd, Cu, Zn) in the gills of a freshwater bivalve, Pyganodon grandis: role of calcium concretions in metal sequestration

Indigenous unionid molluscs, Pyganodon grandis, were collected from nine lakes in the Rouyn–Noranda area (Québec, Canada) along a polymetallic concentration gradient (Cd, Cu, Zn). After excision, the gills were gently homogenised and the cellular compartments were separated by a differential centrifugation procedure that yielded the following particulate fractions: “nuclei + cellular debris”, “mitochondria”, “lysosomes + microsomes” and “granules”. The supernatant remaining after the final ultracentrifugation step, i.e., the operationally-defined cytosol, was separated into a “heat-denaturable proteins” (HDP) fraction and a “heat-stable proteins” (HSP) fraction containing metallothionein (MT). The Cd, Cu and Zn content of each particulate and cytosolic fraction was determined and gill metallothionein was quantified independently by a mercury saturation assay. Cytosolic Cd concentrations were significantly related to the dissolved Cd concentrations at each site, but cytosolic Cu and Zn (essential metals) were not related to their respective ambient dissolved metal concentrations. Metallothionein concentrations increased along the metal contamination gradient and were related to cytosolic Cd (and Zn) in a concentration-dependent manner. However mass balance calculations showed that binding to metallothionein could only account for a small proportion of total gill metal (∼10% Cd; ∼3% Cu; ∼1% Zn). Under these chronic exposure conditions, the three metals (Cd, Cu and Zn) were mainly located in calcium concretions present in the gills (respectively 58 ± 13% of the total gill Cd, 64 ± 6% of the total gill Cu and 73 ± 6% of the total gill Zn). The overall contribution of granules to the total gill dry weight remained relatively constant among the different lakes, suggesting that lake-to-lake variations in granule synthesis were independent of the metal contamination gradient, i.e., these constituent elements of unionid gills act as non-inducible metal sinks at the cellular level. Metal concentrations increased proportionally in both the granules and the MT pool along the polymetallic gradient, suggesting a constant partitioning between these two compartments. Overall, despite an increase in Cd in the “mitochondria” fraction, metal sequestration mechanisms seem to be reasonably effective in detoxifying cadmium: in the cytosol, Cd concentrations in the potentially metal-sensitive HDP fraction remained relatively low and constant, even in specimens collected from the most contaminated lakes.