The effects of titanium nanoparticles on enzymatic and non-enzymatic biomarkers in female Wistar rats.

Titanium dioxide (TiO2) nanoparticles (NPs) are widely used in industry, pharmacy, medicine, and food sectors. Therefore, this study deals with the effects of TiO2 NPs in female rats following oral administration in differing doses for 14 days (0, 0.5, 5, and 50 mg/kg b.w./d). The response of enzymatic biomarkers (Na,K-ATPase, Mg-ATPase, and AChE) was measured in the brain, kidney, and small intestine, while non-enzymatic biomarker levels, such as different forms of glutathione (GSH) and thiobarbituric acid reactive substances (TBARSs) were measured in the liver. The images of the tissues were obtained using a transmission electron microscope (TEM) to demonstrate TiO2 NP accumulation. Data showed that brain AChE activity decreased at all TiO2 NP doses, though brain ATPase activities increased. However, ATPase activities in the intestine and kidney did not change significantly. Levels of GSH forms did not change significantly, though there was a significant decrease in TBARS level at the highest NP dose. TEM images demonstrated that TiO2 NPs accumulated in a dose-dependent manner in the tissues. Data emphasized that the brain was the most sensitive organ against the effects of TiO2 NPs. This study suggests the need for further studies to evaluate better the toxic effects of TiO2 NPs.

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.

Accumulation and Distribution of Nanoparticles (Al2O3, CuO, and TiO2) in Tissues of Freshwater Mussel (Unio tigridis).

Freshwater mussels are used as an effective bioindicator of metal pollution. There is no data on the accumulation of any metal-oxide nanoparticles (NPs) in tissues of Unio tigridis. Thus, this study was undertaken to investigate accumulation of Al2O3, CuO, and TiO2 NPs following exposure to different concentrations (0, 1, 3, and 9 mg/L) of NPs for 14 days. Metal concentrations in tissues were determined by ICP-MS, while NP presence was demonstrated by transmission electron microscope (TEM) images. During the experiments, mussels were fed with cultured algae (Chlorella vulgaris). TEM images demonstrated the presence of NPs in digestive gland and muscle. TEM images also suggested that NPs were taken via the lysosomes or endosomes. Highest mean concentrations (µg/g d.w.) of aluminium (76.51), copper (111.63) and titanium (113.83) occurred in the gills and followed by the digestive glands and muscles. Algae consumption of mussels did not significantly differ among controls and NP-exposed groups.

Antioxidant system biomarkers of freshwater mussel (Unio tigridis) respond to nanoparticle (Al2O3, CuO, TiO2) exposures.

PURPOSE: Mussels are known as the natural filters of the aquatic systems and are accepted as one of the best bioindicator organism. There is no data on the response of Unio tigridis to metal-oxide nanoparticle (NP) exposures. This study aimed to investigate the response of the antioxidant enzymes of U. tigridis following exposure to NPs. MATERIALS AND METHODS: The mussels were exposed to different concentrations (0, 1, 3, 9 mg NP/L) of Al2O3, CuO and TiO2 NPs for 14 days and subsequently, the activities of CAT (catalase), SOD (superoxide dismutase), GPx (glutathione peroxidase), GST (glutathione S-transferase) and GR (glutathione reductase) were measured in the gill and digestive gland. Mussels were fed with cultured unicellular algae (Chlorella vulgaris) during experiments. RESULTS: Data showed that algae consumptions of mussels were not significantly (p>0.05) altered by NPs. However, all enzyme activities in the digestive gland and gill altered significantly (p<0.05) after NP exposures. The activities of CAT and SOD decreased, while the activities of enzymes belonging to glutathione metabolism (GPx and GST) increased in both tissues. CONCLUSION: This study representing the first record on the antioxidant system response of U. tigridis toward NP exposures suggests that NP toxicity should be investigated thoroughly in organisms and some regulations must be done on their usages.

Characterization of antioxidant system parameters in four freshwater fish species.

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

Response of antioxidant system of tilapia (Oreochromis niloticus) following exposure to chromium and copper in differing hardness.

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

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

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

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

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

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

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

Effects of Cd, Zn and Cd + Zn combination on ATPase activitiy in the gill and muscle of tilapia (Oreochromis niloticus).

This study investigated the responses of Na(+)/K(+)-ATPase, Mg(2+)-ATPase and Ca(2+)-ATPase in the gill and muscle of a freshwater fish Oreochromis niloticus exposed to 1 µg/mL of Cd and Zn and their mixture for different periods (0, 7, 14, 21 and 28 days). At the end of experimental periods, the activities Na(+)/K(+)-ATPase, Mg(2+)-ATPase and Ca(2+)-ATPase in gill tissues and only Ca(2+)-ATPase activity in muscle tissues were measured. Gill Na(+)/K(+)-ATPase activity generally decreased following single metal exposures, whereas their combinations increased its activity. Gill Ca(2+)-ATPase activity decreased relative to the control at most exposure times for single exposures of Zn and Cd, as well as for the combined exposure. There was no gill Ca(2+)-ATPase activity after 28 days of exposure to Zn and Cd combined. Mg(2+)-ATPase activity was not affected significantly in gill tissue by exposure to Zn and Cd individually or in combination. Muscle Ca(2+)-ATPase activity also decreased significantly following metal exposure, but not as greatly as in the gill tissue. Tissue protein levels were mostly unaffected by metal exposures. This study showed that certain ATPases are highly sensitive to metal exposure whether the metals are essential or non essential, and suggests using gill tissue Na(+)/K(+)-ATPase and Ca(2+)-ATPase as sensitive biomarkers in metal contaminated waters.

Responses of oxidative stress biomarkers of freshwater fish (Oreochromis niloticus) exposed to Cr6+, Hg2+, Ni2+ and Zn2+ in differing calcium levels.

Freshwaters from different geographical locations show different hardness, affecting metal uptake and toxicity in fish. The most important ion that determines water hardness is calcium. In this study, acute and chronic effects of metals on the oxidative stress biomarkers in the liver of freshwater fish (Oreochromis niloticus) were investigated in differing Ca2+ (30, 60 and 120 mg Ca2+/L) levels. Fish were exposed to Cr6+, Ni2+ and Zn2+ (30 µM) and Hg2+ (0.3 µM) for 3 days in acute experiments, while they were exposed to Cr6+, Ni2+ and Zn+2 (10 µM) and Hg2+ 0.03 µM) for 30 days in chronic experiments. Data showed that the oxidative stress biomarkers significantly (p < 0.05) altered after metal exposures at all calcium levels, though there was no significant change (p > 0.05) among calcium controls. In both acute and chronic exposures, catalase CAT) and superoxide dismutase (SOD) activities increased significantly, while glutathione peroxidase (GPX), glutathione reductase (GR) and glutathione S-transferase (GST) activities decreased. There were significant decreases in total glutathione (GSH) levels in acute exposures, though GSH levels increased in chronic exposures. Malondialdehyde (MDA) levels significantly increased in both durations. The highest significant alterations in the biomarkers occurred at the lowest Ca2+ levels. GPX and GST were found to be the most sensitive enzymes in all exposures and the least alterations in biomarker response occurred in fish exposed to Ni2+. This study demonstrated that calcium levels (hardness) were important factors in the evaluation of metal toxicity for freshwater fish.

Changes in energy reserves and responses of some biomarkers in freshwater mussels exposed to metal-oxide nanoparticles.

In this study, responses of various biomarkers in the digestive gland and foot muscle of freshwater mussels (Unio tigridis) were investigated following exposure to Al2O3, CuO and TiO2 nanoparticles (NPs) for 14 days at different concentrations (0, 1, 3 and 9 mg NP/L). Mussels were fed on unicellular algae (Chlorella vulgaris) cultured in the laboratory. NP exposures caused significant increases (p < 0.05) in the levels of total glutathione (GSH), reduced-glutathione (rGSH), oxidized-glutathione (GSSG) and malondialdehyde (MDA) in the digestive gland. Oppositely, there were significant (p < 0.05) decreases in acetylcholinesterase activity in the foot muscles. Total energy reserves of the digestive gland and foot muscle significantly (p < 0.05) decreased, but only at the highest NP exposures. Nevertheless, NP exposures did not alter (p > 0.05) the algae filtering capacity of mussels. This study demonstrated that the biomarkers belonging to different metabolic systems responded to NP exposures, suggesting their usage in the monitoring studies for freshwater systems.

Salinity and/or nanoparticles (Al2O3, TiO2) affect metal accumulation and ATPase activity in freshwater fish (Oreochromis niloticus).

The osmoregulation system of freshwater fish is sensitive to salinity increase in water. There is no satisfactory data to our knowledge on the accumulation of metal-oxide nanoparticles (NPs) in tissues of O. niloticus and their effects on ATPases (Na,K-ATPase, Mg-ATPase, Ca-ATPase) in differing salinities. Thus, this study investigated the effects of salinity (0 and 10 ppt) and Al2O3 and TiO2 NPs (1 and 10 mg NPs/L) on the response of ATPases in acute (2 days) and chronic (20 days) durations. Data showed that nanoparticles accumulated in the tissues of fish, gill tissues having the highest levels of Al and Ti in both acute and chronic durations. Interestingly, the higher salinity significantly increased (P < 0.05) NP accumulations in the tissues in acute exposures, whereas it significantly decreased (P < 0.05) in chronic exposures. Salinity increase caused significant decreases (P < 0.05) in ATPase activities (up to 54 %) in control fish from both exposure protocols. Likewise, NP alone exposures (up to 80 %) and salt+NP (up to 83 %) exposures generally caused significant (P < 0.05) decreases in ATPase activities compared to their controls. Similarly, salt+NP exposures also decreased ATPase activities compared to NP exposures alone. The present data demonstrated that salinity and/or NP exposures decreased ATPase activities in the gill of freshwater fish, emphasizing the possible hazardous consequences of salt inputs and NP discharges into freshwater systems.

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

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

Characterization of ATPases in the gill of freshwater mussel (Unio tigridis) and effects of ionic and nanoparticle forms of aluminium and copper.

Mussels are often used to monitor the aquatic systems for different ecological aims, as they are one of the best bioindicator animals. However, the characterization of biomarkers should be known before using them in environmental monitoring and toxicology studies. There is no study to our knowledge on the characterization of Na-ATPase and Ca-ATPase in tissues of freshwater mussel (Unio tigridis). Thus, this study was undertaken to characterize the optimum working conditions of Na-ATPase and Ca-ATPase in the gill of mussels, determining the highest levels of parameters (Na+, Mg2+, Ca2+, ATP, pH, temperature, enzyme amount, incubation time) to obtain maximum activity. The present study also aimed to investigate in vitro effects of ionic and nanoparticle (Al2O3, CuO) forms of aluminium and copper (0, 30, 90, 270 µg/L) on the activities of Na-ATPase and Ca-ATPase. Data showed that there was no ouabain-sensitive ATPase activity in the gill up to 10 mM ouabain concentrations. Na-ATPase and Ca-ATPase activities in the gill of control mussels were 5.124 ± 0.373 and 3.750 ± 0.211 µmol Pi/mg pro./h, respectively. Exposure to different concentrations of nanoparticles did not alter significantly (P > 0.05) the activities of Na-ATPase and Ca-ATPase in vitro, whereas the same concentrations of ionic aluminium and copper significantly decreased (P < 0.05) the enzyme activities. Data emphasized that there were different modes of action between ionic and nanoparticle forms of aluminium and copper. Data also suggested that in vivo studies should also be carried out to estimate better the effects of nanoparticle and ionic forms of metals on ATPases of U. tigridis.

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

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

Effects of metal (Ag, Cd, Cr, Cu, Zn) exposures on some enzymatic and non-enzymatic indicators in the liver of Oreochromis niloticus.

Freshwater fish Oreochromis niloticus exposed to 0.05 microg/mL of Cu, Cd, Zn, Ag and Cr for up to 30 days. Only Ag, which exceeded environmentally realistic concentrations by a factor of >100 caused fish mortality within this period. Metals increased aspartate transaminase (AST) activity, while they decreased alanine transaminase (ALT) activity, except Cr exposure. Concentrations of free -SH group decreased whereas protein concentrations did not alter following metal exposures. Detectable metal accumulation occurred in the liver of Cd, Cu and Zn exposed fish. This study emphasized that both enzymatic and non-enzymatic mechanisms may be useful in understanding the degree of metal toxicity in fish liver.

Responses of biomarkers belonging to different metabolic systems of rats following oral administration of aluminium nanoparticle.

Nanoparticle (NP) forms of aluminium oxide (Al2O3) are used in various fields such as engineering, pharmacy, medicine etc. Compounds containing aluminium oxide NPs may present toxic effects after certain thresholds. Thus, the present study was carried out to determine the effects of Al2O3 nanoparticles (Al-NPs) in rats. For this aim, different doses (0, 0.5, 5, 50 mg/kg b.w./day) of Al NP (˜40 nm) were orally administered to female rats (Rattus norvegicus var. albinus) for 14 days and the response of several biomarkers such as activities of ATPases (total ATPase, Na,K-ATPase, Mg-ATPase) and acetylcholinesterase (AChE), levels of different glutathione forms and thiobarbituric acid reactive substances (TBARS) were measured in different tissues. Additionally, tissue accumulation of Al-NPs was demonstrated by a transmission electron microscope (TEM). The images showed the presence of Al-NP aggregates in all the tissues at all doses. The sizes of NP aggregates were dependent on NP doses and it was a bit more loose in the brain than in the liver and kidney. AChE activity in the brain decreased significantly at all NP doses, whereas TBARS levels in the liver did not alter significantly at any NP dose. Although there was no significant change in ATPase activities in the intestine at any NP dose, there were significant decreases in the kidney and brain. There were some variations in the levels of total glutathione (tGSH), oxidized glutathione (GSSG) and reduced glutathione (rGSH), though these variations were not significant (P > 0.05). Likewise, the ratio of rGSH/GSSG also did not differ significantly among NP doses and control. The brain seems most affected organ following Al-NP administration. This study demonstrated that most biomarkers in the tissues of rats were affected by Al-NP, showing the signal of toxic effects and suggests further studies to understand better the effects of Al NPs, especially in their use for pharmacology.

Response of the antioxidant enzymes of rats following oral administration of metal-oxide nanoparticles (Al2O3, CuO, TiO2).

Metal-oxide nanoparticles (NPs), as a new emerging technological compound, promise a wide range of usage areas and consequently have the potential to cause environmental toxicology. In the present work, aluminum (Al2O3), copper (CuO), and titanium (TiO2) nanoparticles (NPs) were administered via oral gavage to mature female rats (Rattus norvegicus var. albinos) for 14 days with a dose series of 0 (control), 0.5, 5, and 50 (mg/kg b.w./day). Enzyme activities of the antioxidant system such as catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione S-transferase (GST), and glutathione reductase (GR) in the liver were measured. Transmission electron microscope (TEM) images of the liver were taken to demonstrate NP accumulation and distribution in liver tissue. Data showed that all NPs caused some significant (P > 0.05) alterations in the activities of antioxidant enzymes. CAT activity increased after CuO and TiO2 administrations, while SOD activity decreased after Al2O3 administration. The activities of enzymes associated with glutathione (GR, GPx, GST) metabolisms were also significantly altered by NPs. GPx activity increased in rats received Al2O3, CuO NPs, while GR activity increased only by Al2O3. However, there were increases (TiO2) and decreases (CuO) in GST activity in the liver of rats. TEM images of the liver demonstrated that all NPs accumulated in the liver, even at the lowest dose. This study indicated that the antioxidant enzymes in the liver of rats were affected by all NPs, suggesting the antioxidant system of rats suffered after NP administration.

Changes in serum biochemical parameters of freshwater fish Oreochromis niloticus following prolonged metal (Ag, Cd, Cr, Cu, Zn) exposures.

Fish serum may reflect status of many biochemical processes in the metabolism. Heavy metals, as environmental stressors, may alter serum biochemical parameters in fishes. Thus, freshwater fish, Oreochromis niloticus, were exposed to low levels (0.05 mg/L) of metals (silver [Ag], cadmium [Cd], copper [Cu], chromium [Cr], zinc [Zn]) to investigate responses of serum biochemical parameters over different exposure periods (0, 5, 10, 20, 30 d). Fish mortality occurred only in Ag exposure, as all fish died between days 12 to 16. Activities of alkaline phosphatase (ALP), alanine transaminase (ALT), and aspartate transaminase (AST) were altered only in Cu- and Cd-exposed fish. Both Cd and Cu exposures decreased the activity of ALP, although they increased the activities of ALT and AST. Glucose concentrations increased in Ag-, Cd-, and Cu-exposed fish, with a sharp increase occurring in Ag-exposed fish before mortality began. Total protein and triglyceride concentrations increased in Ag-exposed fish, although they decreased in Cu-exposed ones. However, all metal exposures increased cholesterol concentration in the serum. Concentration of blood urea nitrogen increased in Ag-, Cd-, and Cu-exposed fish, although it decreased in Cr-exposed ones. Calcium level decreased only in Cu-exposed fish, and Cl(-) level decreased in Ag-exposed fish. Silver and Cu exposures also decreased Na(+) level in the serum. Cadmium and Cu exposures increased serum K(+) levels. The present study, investigating the effects of environmentally realistic metal exposures on serum biochemical parameters, demonstrated that fish serum could sensitively reflect environmental metal stress. Thus, it suggests that serum biochemical parameters could be used as important and sensitive biomarkers in ecotoxicological studies concerning the effects of metal contamination and fish health.