Cd In Gills Research Articles

Bioaccumulation and sub-lethal physiological effects of metal mixtures on mussel, Mytilus edulis: Continuous exposure to a binary mixture of mercury and cadmium

In the natural ecosystem, aquatic organisms are exposed to a cocktail of chemicals that may result in toxicological responses differing from those of individual chemicals. In the present study, mussels were exposed using a semi-static and triplicated design to either control (no added metal), 50 µg l−1 (Hg alone), 50 µg l−1 (Cd alone), or 50 µg l−1 Hg plus 50 µg l−1 Cd (Hg + Cd) mixture for 14 days. Tissues were collected on days 0, 2, 4, 8, and 14 for metal analysis and sub-lethal responses using a suite of assays. Tissue metal concentrations were not significantly different in the single metal (Hg or Cd) compared to the Hg plus Cd mixture treatment for all tissues, apart from the gill of the Cd alone treatment. At the end of the experiment, the gill Cd concentration was significantly increased in the Hg plus Cd mixture compared to the Cd alone treatment, suggesting the influence of Hg on Cd uptake. The percentage increases of the Hg plus Cd mixture compared to the arithmetic sum of the individual metals were ( %): 20.2, 9.3, 25.1, 23.8, 10.7, and 12.4 for adductor muscle, digestive gland, gill, gonad, remaining soft tissue, and haemolymph, respectively. There were no observed treatment effects on total haemocyte count, haemolymph protein, or glucose concentration in the cell-free haemolymph. Neither was there any treatment effect on osmotic pressure, ions in the tissues, or in the cell-free haemolymph. At the end of the experiment, Hg-mediated oxidative damage, as an increase of thiobarbituric reactive substances (TBARS) and apparent depletion of total glutathione. This was observed in the gill and digestive gland of the Hg alone and Hg plus Cd mixture. Histopathology examination showed similar pathology in the Hg alone and the Hg plus Cd treatment. In conclusion, despite some oxidative stress and pathology during metal exposure, the accumulation of metals and effects on mussel health were similar between single exposures and a mixture of Hg plus Cd. In terms of risk assessment, regulations for the individual metals should suffice to protect against the mixture of Hg plus Cd, at least for adult M. edulis in full-strength seawater.

Effect of acute cadmium exposure on oxidative stress and antioxidant system of the scallop Aequipecten tehuelchus

This study aimed to assess the impact of acute exposure (96 h) to Cd in gills, digestive gland and muscle of the Tehuelche scallop Aequipecten tehuelchus from San José gulf in Patagonia, Argentina. Scallops were exposed to Cd concentrations of 0, 25, 50, 100, 150, 204, 275, 371, and 500 μg/L, and mortality rates were recorded after 96 h of exposure. Surviving organisms were analyzed for the biochemical response through reactive oxygen and nitrogen species (RONS), activities of catalase (CAT) and glutathione-S-transferase (GST), metallothioneins (MT), lipid peroxidation (LPO) and liposoluble antioxidants α-tocopherol (α-T) and β-carotene (β-C). The mean lethal concentration (LC50) was 155.8 μg Cd/L, a lower value than other scallops' species, showing that A. tehuelchus has a particular sensitivity to Cd. In the three tissues, at all exposure concentrations, there was no significant response in RONS levels, GST activity or LPO. Nevertheless, CAT activity and α-T levels decreased in the gills but increased in the digestive gland, with no significant response in the muscle. Two-way ANOVA revealed a significant interaction between Cd concentration and tissue on MT, which increased significantly in gills, decreased in digestive gland with 100 compared to 50 μg Cd/L; whereas in muscle a significant increase was observed with 25 μg Cd/L compared to control. The results show a significant effect of Cd in scallop's gills on CAT activity and α-T levels, highlighting this tissue as the primary target against relevant concentrations of metal in seawater. The effect on digestive gland and muscle was minimal. The overall results suggest that Cd toxicity is tissue-specific. This study will help reduce the existence knowledge gap regarding potential impacts of acute exposure to Cd in a bivalve species with high ecological and commercial importance, as well as identifying the most responsive biomarkers associated with Cd stress for monitoring assessment.

Modulation of Cd and BaP uptake rate during acute aqueous co-exposure in adult zebrafish (Danio rerio)

Cadmium and Benzo[a]pyrene are two toxicants of great environmental importance given their frequency and ability to cause extensive toxicity in aquatic organisms including fish. There is evidence that fish can modulate their respective uptake rate during simultaneous exposures, albeit the mechanism behind this is poorly understood. The present study aimed to examine this interaction by exposing adult zebrafish to either 89.3 nM Cd, 4.25 nM BaP or a combination of the two for 72 hrs prior to examining the uptake rate of either toxicant via short-term exposures (3–6 hrs) to radiotracers (109Cd and 14C-BaP). Our results showed that Cd uptake rate increased significantly in the gills when animals were pre-exposed to both toxicants simultaneously, resulting in an increased maximum uptake rate (Jmax). The increased Cd uptake rate did not correspond to increased expression of gill Cd transporters such as the epithelium calcium channel (ECaC) or the divalent metal transporter 1 (DMT1). Furthermore, BaP uptake rate increased significantly at the whole-body level when animals were exposed to both 5.03 nM 14C-BaP and 89.3 nM Cd concurrently. Additionally, we ran a time-course and observed BaP uptake rate is highest in the 6–12 hrs following the beginning of the exposure. Our results provide evidence that the increased bioaccumulation of Cd and BaP observed during co-exposures is at least in part due to an increase in uptake rate and is driven by separate mechanisms.

Elements in Mediterranean mussels from Istanbul and exposure assessment

ABSTRACT In this study, concentrations of elements were determined in edible tissues of Mytilus galloprovincialis by means of inductively coupled plasma mass spectrometry (ICP-MS). The mean levels (mg kg−1) of 0.67 for Cd, 6.9 for As, 0.79 for Pb, 2 for Ni, and 42.6 for Zn exceeded the maximum limits in the digestive glands. Also, the mean concentrations of Cd and As in muscle and of Cd and Ni in gills were above the maximum limits. The highest value was found for As in a digestive gland, with 65.4% of the Provisional Tolerable Weekly Intake. In addition, the lowest percentage belonged to Zn with 0.2% of PTWI in muscles and 0.3% of PTWI in gills of the mussels. Mercury concentrations were well below legal limits.

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.

Risk assessment of human exposure to lead and cadmium in tissues of Blackchin Tilapia (Sarotherodon melanotheron) from an intertidal creek in the Niger Delta region of Nigeria

The present study investigated the risk associated with concentrations of lead and cadmium in tissues (gills, livers and muscles) of Blackchin tilapia (Sarotherodon melanotheron) from upstream and downstream regions of an intertidal creek in Rivers State, Nigeria. The trend of Cd in fish tissues and water was as follows: muscle > liver > gills > water. The concentration of Cd in fish gills was higher in downstream fish when compared to upstream fish. The mean Cdmg kg −1 in fish gills was 0.048 ± 0.015—upstream and 0.549 ± 0.152—downstream, 0.037 ± 0.030—upstream and 0.769 ± 0.100—downstream, 0.026 ± 0.015—upstream and 0.902 ± 0.118—downstream, and 0.040 ± 0.018—upstream and 0.727 ± 0.157—downstream in December, January, February and March respectively. The trend of Pb in fish tissues and water was as follows: muscle > liver > gills > water. Pb was generally higher in fish sampled downstream when compared to those sampled upstream of the creek. Fish gills in upstream fishes had Pb of 6.324 ± 0.388 mg kg−1, 5.140 ± 1.249 mg kg−1, 5.459 ± 0.471 mg kg−1 and 5.730 ± 0.859 mg kg−1 while downstream fishes had Pb 7.732 ± 0.640 mg kg−1, 9.401 ± 0.711 mg kg−1, 7.575 ± 0.624 mg kg−1 and 7.644 ± 0.637 mg kg−1 in December, January, February and March respectively. Cdfish gills < Food and Agriculture Organization (FAO) maximum permissible limit (MPL), Cdfish muscles and Cdlivers < MPL for FAO, FAO/WHO and WHO. Pbgills upstream and downstream > MPL for FAO, FAO/WHO and WHO. Pb and Cd did not indicate non-carcinogenic risks to human health owing to the consumption of fish up- and downstream. In the present study, fishes sampled upstream showed low cancer risk in adults, however, cancer risk index (CRI) indicated moderate cancer risk in children (male and female). For fishes sampled downstream, CRI indicated low risk for adults and male children, but a moderate risk for female children.

Determination of Nickel and Cadmium in Freshwater Fishes at Sungai Kuantan, Sungai Riau And Sungai Pinang

Heavy metal exhibit toxic and persistent characteristics, can enter into the food chains and the ecosystem where they cause adverse impact on the biotic and abiotic components of ecosystem. Heavy metal pollution in Malaysia has become a major health concern for humans. Thus, this study was conducted to determine the level of cadmium (Cd) and nickel (Ni) in the muscle and gill of fishes collected from the Sungai Kuantan and Sungai Riau. Field sampling was conducted between September and December 2017. Five different species of fishes: Barbonymus gonionotus (Lampam Jawa), B. schwanenfeldii( Lampam Sungai), Hampala macrolepidota(Sebarau), Chitala chitala (Belida), and Hemibagrus nemurus(Baung) were digested by using acid digestion method and analysed with Inductively Coupled Plasma-Mass Spectrometry (ICPMS). Concentration of Cd among species were in order of: H. macrolepidota &gt;B.gonionotus&gt; B. schwanenfeldii&gt; C.chitala&gt; H.nemurus, whereas Ni level in fishes were: C. chitala&gt; H. macrolepidota&gt; B. gonionotus&gt; H. nemurus&gt; B. schwanenfeldii. Among all the species, H. macrolepidota from Sungai Kuantan had the highest Cd in both muscle (0.1761±0.0062¬mg/kg) and gills (0.2938±0.0066mg/kg) whereas the highest Ni level in muscle was noted in C. chitala from Sungai Kuantan with (0.1473±0.0755 mg/kg) and in gills of B.gonionotus (0.4544±0.0470mg/kg) from the same river respectively. It was obtained that there was a significant difference (p&lt;0.05) of Cd in muscle between species. Ni concentration in fishes was below the permissible limit stipulated by World Health Organizations WHO (1985) and Food and Agriculture Organizations (2012) but the concentration of Cd was recorded high. However, it was still below the World Health Organization (WHO) 1985 and Malaysian Food Act (MFA) 1983.

Gill Histopathological Biomarkers in Fish Exposed to Trace Metals in the Todos os Santos Bay, Brazil.

Histopathologies are widely recognized as biomarkers of environmental pollution. In this sense, we evaluated the putative relationship of gill histopathologies and distinct ecological impacts in two regions of Todos os Santos Bay (BTS), Brazil, the largest bay in Northeastern Brazil, South Atlantic. We compared the presence and concentration of metals (Al, As, Ba, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, V, and Zn) in water, sediments, and gills and gill histopathologies of a demersal fish (Diapterus rhombeus) and a benthic fish (Ogcocephalus vespertilio). As expected, fish and sediment samples from historically contaminated areas (Aratu) showed more remarkable traces of metals than apparently low-impact areas (Jaguaripe). Likewise, the DTC (degree of tissue change) index and the volume densities were higher in fish caught in Aratu. In addition, the Diapterus rhombeus species showed more potential than Ogcocephalus vespertilio for risk assessment as it showed more responses to the environment reflected on more histopathologies. These data support the effectiveness of incorporating functional gill morphology to monitor impacts on estuarine biota that can be used as a reference to improve the management of ecosystems and prevent harm to human health.

Non-enzymatic antioxidant responses of Mytilus galloprovincialis: Insights into the physiological role against metal-induced oxidative stress

The exposure to metals is known to generate oxidative stress in living organisms, which can result in the induction of protective antioxidant defences, both enzymatic and non-enzymatic. This work aims to obtain new data on the existing links among several non-enzymatic components of the antioxidant system, that are physiologically related to both metal sequestration and defense against metal-induced oxidative stress, using the blue mussels (Mytilus galloprovincialis) as a model organism. Specimens of this marine bivalve were experimentally exposed to cadmium (Cd), used as oxidative stress inducer. Cd, metallothionein (MT), glutathione (GSH), malondialdehyde (MDA) contents, and glutathione reductase (GR) activity in gills and in digestive glands were assessed at 0, 12, 24, 48, 72 and 96 h. The obtained results provide new data about the relationships among the non-enzymatic antioxidant cellular components considered in this study. These constitute the prompt physiological responses to the oxidative stress in blue mussels exposed to Cd in controlled laboratory conditions.

Levels of metals in fish tissues of Liza haematocheila and Lateolabrax japonicus from the Yellow River Delta of China and risk assessment for consumers

The Yellow River Delta (YRD) is an important spawning and nursery area for numerous fishes. The concentrations of Fe, Al, Mn, Zn, Ni, Cr, Cu, Co, Pb and Cd in muscle, liver, gills and skin of two broadly distributed commercial fish in the YRD were analyzed. The results demonstrated that liver and gills displayed higher accumulation ability of metals than other tissues, while muscle always accumulated the lowest concentrations of metals. Generally, significant opposite relationships (p < 0.05) were observed between fish size and metals in fish tissues especially in muscles of both fish species which may be explained by the lower feeding rate, stronger detoxification and elimination mechanisms in the bigger individuals. All metals in muscles were well below the proposed toxic limit. Besides, the toxic effects were not expected to occur for the consumption of muscles of studied fish according to the results of human health risk assessment.

Heavy Metals in Tissues of Blue Crabs Callinectes danae from a Subtropical Protected Estuary Influenced by Mining Residues.

This short note aims to report in detail a preliminary assessment of the concentrations of Cd, Hg and Pb in tissues of blue crabs Callinectes danae collected from the Cananéia-Iguape-Peruíbe estuarine complex (CIP), in the South of São Paulo State coast, Brazil. In October 2014, blue crabs were collected from CIP. Tissues were removed by dissection and metal determination was performed by GF-AAS and CV-AAS. According to statistical analysis, Pb and Cd concentrations in gills were significantly higher than those found in muscles and hepatopancreas, respectively. There were no significant differences in Hg concentrations between samples. Cd, Hg and Pb concentrations in gills and hepatopancreas were lower than those reported in a previous study performed at CIP. However, Cd concentration in hepatopancreas was higher than the Brazilian limit for consumption and new efforts to monitor Cd concentrations in C. danae tissues must be performed.

Larimichthys crocea is a suitable bioindicator for monitoring short-term Cd discharge along the coast: An experimental study

The present study evaluated the feasibility of using a marine cage fish Larimichthys crocea as a model for monitoring short-time Cd discharge near the sewage outlet. Fish were exposed to 0, 20, 100, 500 and 2500 μg/L for 6 h. Cd concentrations in gills, and left and right lobes of hepatopancreas were examined as well as activity levels of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathion-S-transferase (GST), glutathione reductase (GR), lipid peroxidation, glutathione (GSH) and mRNA levels of 19 genes encoding these enzymes. Cd concentrations increased at 100, 500 and 2500 μg/L Cd in gill and at 2500 μg/L Cd in hepatopancreas. Lipid peroxidation increased and GSH levels declined in gills at 2500 μg/L Cd. On the contrary, oxidative damage was not observed in hepatopancreas but GSH levels increased at all tested concentrations of Cd in the left lobe and at 20 μg/L Cd in the right lobe. The enhanced antioxidant response was confirmed in gills due to the increased activity levels of antioxidant enzymes and the up-regulated mRNA levels of most genes. However, disordered antioxidant response was observed in hepatopancreas, showing a dose- and lobe-dependent effect. RNA-seq and q-PCR analyses were performed to investigate differently expressed genes between both lobes under different concentrations of Cd. The most significantly enriched pathway term was pancreatic secretion, where the right lobe showed higher mRNA levels of 18 genes encoding pancreatic digestive enzymes than the left one under Cd stress. Interestingly, both lobes had the same mRNA levels of digestive enzyme genes and antioxidant genes in fish without Cd exposure. Overall, Larimichthys crocea is very sensitive to environmental exposure to cadmium. The present study for the first time investigates Cd-induced antioxidant response in Larimichthys crocea, also is the first to find lobe-dependent effects in fish.

Heavy Metals Content in Tissues of Feather back Fish (Notopterus notopterus) from the Sail River, Pekanbaru

This study aimed to determine the concentrations of heavy metals (Cd, Cr, Pb, Zn, Fe, and Cu) in gills, muscles, kidney, bone, liver, and reproductive organs of Notopterus notopterus from the Sail River. The results shown that the concentrations of heavy metals in each tissues of fish were as follow: muscles > reproductive organs > liver > kidney > gills and bone for Cd; liver > bone > kidney > muscles > reproductive organs > gills for Cr; gills > kidney > bone > muscles > liver > reproductive organs for Pb; gills > bone > reproductive organs > kidney > liver > muscles for Zn; gills > muscles > liver > kidney > reproductive organs > bone for Fe; bone > liver > kidney > muscles > gills > reproductive organs for Cu. Concentrations of Cr (95.62 mg/kg) was highest than 5 others heavy metals. The average of metal concentrations of Pb (35.62 mg/kg), Zn (88.47 mg/kg), and Fe (2.35 mg/kg) were highest in the gills. The estimated concentrations of Cd, Cr, Pb, Fe were higher and Zn, Cu were lower than the limits permitted.

ITRAQ-based proteomic analysis on the mitochondrial responses in gill tissues of juvenile olive flounder Paralichthys olivaceus exposed to cadmium

Cadmium (Cd) is an important heavy metal pollutant in the Bohai Sea. Mitochondria are recognized as the key target for Cd toxicity. However, mitochondrial responses to Cd have not been fully investigated in marine fishes. In this study, the mitochondrial responses were characterized in gills of juvenile flounder Paralichthys olivaceus treated with two environmentally relevant concentrations (5 and 50 μg/L) of Cd for 14 days by determination of mitochondrial membrane potential (MMP), observation of mitochondrial morphology and quantitative proteomic analysis. Both Cd treatments significantly decreased MMPs of mitochondria from flounder gills. Mitochondrial morphologies were altered in Cd-treated flounder samples, indicated by more and smaller mitochondria. iTRAQ-based proteomic analysis indicated that a total of 128 proteins were differentially expressed in both Cd treatments. These proteins were basically involved in various biological processes in gill mitochondria, including mitochondrial morphology and import, tricarboxylic acid (TCA) cycle, oxidative phosphorylation (OXPHOS), primary bile acid biosynthesis, stress resistance and apoptosis. These results indicated that dynamic regulations of energy homeostasis, cholesterol metabolism, stress resistance, apoptosis, and mitochondrial morphology in gill mitochondria might play significant roles in response to Cd toxicity. Overall, this study provided a global view on mitochondrial toxicity of Cd in flounder gills using iTRAQ-based proteomics.

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.

Macro- and trace elements in Chinese mitten crabs (Eriocheir sinensis) from Szczecin Lagoon, Poland – Implications for human health

Chinese mitten crab (Eriocheir sinensis) is a valued foodstuff in China. However, their elemental composition is still poorly understood. Therefore, the aim of this study was to quantify the concentrations of Al, As, Ca, Cd, Cu, Fe, K, Mg, Na, Ni, Pb, Se, and Zn in muscle, hepatopancreas, gonads, gills, and exoskeletons of E. sinensis caught in spring and autumn in the Szczecin Lagoon, and to compare these levels to Dietary Reference Intake. High levels of Ca (>20, 000 μg g−1) in the exoskeleton, K (5,980 μg g−1) and Zn (80.8 μg g−1) in muscle, Ni (0.678 μg g−1) and Cd (0.3278 μg g−1) in the hepatopancreas, As (0.0411 μg g−1) and Se (0.3208 μg g−1) in the gonads, Fe (204 μg g−1), Cu (59.0 mg g−1), and Pb (0.0742 mg g−1) in the gills were measured. The edible parts of E. sinensis caught in Poland can be a valuable source of macro- and microelements important in human diet. Levels of Pb and Cd did not exceed the established food safety level of 0.50 μg g−1. The results showed that introduction of commercial fishing of this species may be profitable and would also comply with the European Union's legal regulations concerning the reduction of invasive animal populations in Europe.

Metallothionein expression on oysters (Crassostrea cuculata and Crassostrea glomerata) from the southern coastal region of East Java

Background: This study aimed to analyse levels of heavy metals (Pb, Hg and Cd) in the aquatic body, gills and stomach of the oysters Crassostrea cuculata and Crassostrea glomerata, the metallothionein (MT) level in the gills and stomach of both oysters, and relationships between heavy metals level (Pb, Hg and Cd) in the gills and stomach to MT level in both types of oysters. Methods: The research method utilized was a descriptive method. The oyster samples were taken from three stations: Sendang Biru, Popoh and Prigi beaches. MT values were assessed using confocal laser scanning microscopy. The heavy metal levels were assessed using atomic absorption spectrophotometry method. Results: Both oyster heavy metal content obtained in the southern coastal waters exceeded the safe limit set by the State Minister of Environment No. 51 of 2004. In general, the expression of MT was found to be higher in gastric tissue compared to gill tissue. Conclusions: The relationship between levels of the heavy metals Pb, Hg, and Cd in oyster gills and stomach has a strong relationship with MT levels in the gills and stomach in both types of oysters.

Distribution of Al, Cd, Cu, Fe, Mn, Pb and Zn in Liver, Gills and Muscle of Early Life Stages of Atlantic Salmon (Salmo salar).

The aim of this study was to determine metal distribution in different tissues in early life stages of Atlantic salmon. The concentrations of the metals Al, Cd, Cu, Fe, Mn, Pb and Zn in liver, gills, muscle of fish and water from a salmon farm in the Region de los Lagos of southern Chile were determined. Results show that Cd and Pb had the lowest concentrations, while Zn the highest concentration, followed by Cu, Fe and Mn. Cu and Fe had the highest concentrations in liver, while Mn and Zn were the highest in gills. Cu and Fe in liver were higher in pre-smolts than in fingerlings. Cu had the highest bioaccumulation factor in pre-smolts, both in liver and gills. In conclusion the metals tend to bioaccumulate selectively in different tissues of Salmo salar. Liver is the most relevant for Cu and Fe, and liver and gills for Zn.

Toxicokinetic and toxicodynamic (TK-TD) modeling to study oxidative stress-dependent toxicity of heavy metals in zebrafish

Adverse outcome pathways (AOP) have been proposed as a new method to improve the ecological risk assessment of pollutants, but it requires quantitation linkage between exposure, biomarker response and toxicity of pollutants. A toxicokinetic and toxicodynamic (TK-TD) model was used to quantify AOP of the toxicity of Cd and Pb to zebrafish, including the quantitative relationship between Cd and Pb accumulation in gill and oxidative damage level based on ROS or MDA, and LC50 values at different times. Significant relationships were found between the oxidative damage level characterized by ROS and MDA content and Cd or Pb accumulation in gill (R2 > 0.60), and the TK model could better simulate the Pb accumulation in the gills (R2 > 0.60) than Cd. The increasing of Cd or Pb concentrations induced the generation of ROS and the formation of ROS initiated the fluctuation of MDA level in the cells as compared to controls (p < 0.05). For the individual level effect, the Damage Assessment Model (DAM) could successfully explain the change of LC50-ROS and LC50-MDA values at different times (R2 > 0.99). Our findings suggested that the TK-TD model based on ROS and MDA could be used as a quantitative AOP to predict toxicity of metals to zebrafish.

Influence of microplastics on the accumulation and chronic toxic effects of cadmium in zebrafish (Danio rerio)

As the accumulation of microplastics (MPs) in the environment continues to rise, more concerns focus on the health risk of combined exposure to MPs and other contaminants. The aim of this study is to investigate the influences of MPs on the tissue-accumulation of cadmium (Cd) in zebrafish and explore the related chronic toxic effects induced by combined exposure of Cd and MPs. After co-exposure to MPs and Cd for 3 weeks, 20 and 200 μg/L MPs increased the accumulation of Cd in zebrafish livers (46% and 184%), guts (10% and 25%) and gills (9% and 46%). The Cd accumulation was gill > gut > liver. Comprehensive analyzes of biochemical biomarkers, histopathological observation and functional gene expression firstly demonstrated that the presence of MPs enhanced the toxicity of Cd on zebrafish and the combined exposure caused oxidative damage and inflammation in zebrafish tissues. Collectively, our results highlight the chronic effects of combined exposure to MPs and heavy metals.