Sublethal Levels Of Copper Research Articles

Influence of preexposure to sublethal levels of copper on 64Cu uptake and distribution among tissues of the European eel ( Anguilla anguilla)

The effect of preexposure to copper was examined in European eels with respect to uptake and distribution of 64Cu among tissues. Eels were exposed in freshwater to 8 and 64 μg Cu · L −1 for 0, 6 and 28 days before 64Cu incubation. The accumulation of copper in gill, liver and muscle tissue was studied by the uptake of 64Cu during 67 hr of exposure to 8 and 64 μg · L −1. The Cu accumulation rate in muscle tissue was inversely related to bodyweight. Although the accumulation rates in liver and muscle tissues were significantly reduced after 6 and 28 days of preexposure to 64 μg · L −1 (but not to 8 μg · L −1), the accumulation rates in the gills were not affected by preexposure. We suggest that the excretion rate of copper was stimulated by the applied preexposure to 64 μg Cu · L −1.

Brain monoamine levels and energy status in common carp ( Cyprinus carpio) after exposure to sublethal levels of copper

Serotonin (5-hydroxytryptamine, 5-HT) and dopamine (DA) are two major monoamine neurotransmitters with a multitude of functions in the vertebrate brain. In fish, the 5-HT system has been shown to be sensitive to various forms of stress, but very few studies have examined the effects of toxic metals on these monoamine systems. Juvenile common carp were exposed to copper levels of 0.22, 0.34 and 0.84 μM during 1 week. In telencephalon, dose-dependent falls in 5-HT and DA levels were observed, with approximately 50% losses of these neurotransmitters at the highest copper concentration. Although less dramatic, falls were also seen in 5-HT and DA levels in hypothalamus and brain stem. No changes in 5-hydroxyindoleacetic acid (5-HIAA, the main 5-HT metabolite), AMP, ADP, ATP, adenylate energy charge or lactate levels were observed in brain. However, lactate levels in blood plasma increased with copper concentration. A significant copper accumulation only occurred in the liver, while no changes in brain or muscle were seen. It is concluded that copper exposure of common carp causes decreased brain 5-HT and DA levels, two neurotransmitters involved in, for example, feeding behaviour and locomotor control in fish. In fact, in telencephalon a fall in 5-HT levels was seen already at a copper concentration below that where food intake and movement were impaired.

Plasma ammonia concentration in brown trout in soft acidic water and its relationship to decreased swimming performance

Adult brown trout (300­600 g) were acclimated for 2 weeks to an artificial soft water (Ca2+, 50 µmol l-1) and maintained at either 5 °C (October to March) or 15 °C (May to August). Following insertion of a cannula into the dorsal aorta under MS-222 anaesthesia and a recovery period of 2 days, the fish were exposed to a 4 day episode of sub-lethal copper levels at pH 5 or kept at control conditions of pH 7 without copper. The copper concentrations had been predetermined by toxicity testing and were approximately 0.47 µmol l-1 at 5 °C and 0.08 µmol l-1 at 15 °C. At 5 °C, a group of fish was also exposed to approximately 0.08 µmol l-1 copper at pH 5. Plasma total ammonia (Tamm) concentration was significantly elevated by exposure to copper and pH 5. In resting trout exposed to the appropriate sub-lethal copper concentration at pH 5, Tamm was six and 7.5 times greater at 5 and 15 °C, respectively, than those of control trout at the respective temperatures. Although unconfirmed, an elevation of ammonia production alone seems unlikely to account for such substantial increases. From previous studies, there is little evidence of impairment of respiratory gas exchange in trout exposed to these copper concentrations and yet, in the acidic test waters, the gradient of NH3 partial pressure between fish and water was 5.5­6 times greater than that under control conditions. Swimming performance determined by the critical swimming speed (Ucrit) was reduced by copper and acid exposure, and a significant relationship existed between Ucrit and the plasma ammonia concentration of exercised trout. Ammonium ions influence several key enzymes involved in energy metabolism, and elevated ammonia levels might, therefore, reduce the capacity of muscle to exercise. Alternatively, ammonia may have affected the nervous coordination of exercise either centrally or by disrupting peripheral motor innervation.

The effect of sublethal levels of copper on oxygen consumption and ammonia excretion in the common carp, Cyprinus carpio

Common carp ( Cyprinus carpio) of 15–30 g body weight were exposed to copper levels of 0.22 ± 0.07, 0.34 ± 0.12 and 0.84 ± 0.35 μmol · l −1. Oxygen consumption and nitrogen excretion were determined repeatedly for up to 2 weeks of exposure to copper. Critical oxygen concentrations for oxygen consumption as well as for ammonia excretion were determined after 1 week of exposure to copper. Oxygen consumption dropped significantly immediately after exposure to 0.34 and 0.84 μmol · l −1 of copper whereas nitrogen excretion remained stable. After 1 week of continuous exposure to 0.34 μmol · l −1 of copper the oxygen consumption showed an apparent recovery, while the ammonia quotient (AQ = mole to mole ratio of ammonia excreted to oxygen consumed) did not. At a copper concentration of 0.84 μmol · l −1, no recovery was observed. The critical oxygen concentration for oxygen consumption shifted from 45 μmol · l −1 (1.4 mg · l −1) in copper-free water to 126 μmol. l −1 (3.9 mg · l −1) at a copper concentration of 0.34 μmol · l −1. At 0.84 μmol · 1 −1, regulation of oxygen consumption was lost. Also ammonia excretion showed a decline at lower oxygen concentrations and a critical oxygen concentration for ammonia excretion was determined. For the nitrogen excretion, loss of regulation already occurred at copper concentrations of 0.34 μmol · l −1. For the AQ, no critical oxygen concentration was found. The results obtained in this study suggest that measurements of oxygen consumption in combination with measurements of nitrogen excretion can be useful indicators of stress. Furthermore, it is shown that a critical oxygen concentration for ammonia exists in carp and that the critical oxygen concentrations for oxygen consumption and for ammonia excretion are affected by exposure to copper.

Electrophoretic analysis of polypeptides of Prorocentrum micans Ehrenberg exposed to toxic levels of copper

The effects of toxic levels of copper in the dinoflagellate Prorocentrum micans Ehrenberg were investigated by analysis of SDS-PAGE polypeptide profiles. Sublethal levels of copper added to exponentially growing batch cultures induced evident alterations in the growth of the cultures and in the soluble protein concentration per cell (51% reduction of the number of cells and 36% of the total soluble protein content, after 14 days of 3.94 μM copper exposure). The highest copper concentration (7.87 μM) clearly inhibited the culture growth. The SDS-PAGE polypeptide profiles of control and 14 days copper treated cultures extracts, showed the presence of similar polypeptides between ca. 30 and 110 kDa, but the relative amounts of some of them was changed. Using as reference in each profile the most preeminent polypeptide (33.5 kDa), a reduction of the amounts of the 35 and 39.5 kDa polypeptides and an increase of the 42, 46, 47.5 and 104 kDa ones were observed when compared to the control. The results indicate the occurrence of copper toxicity at the protein level in P. micans, as well as interference in the growth of the cultures.

The effect of sublethal levels of copper and cyanide on some biochemical parameters of rainbow trout along subacute exposition

1. The stress responses of juvenile rainbow trout ( Oncorhynchus mykiss) sublethally exposed to copper and cyanide was studied. 2. Copper and cyanide caused rapid elevations ( p < 0.0001) of plasma cortisol levels (185ng/ml for copper, 305 ng/ml for cyanide) observed in 1 hr and maintained throughout the experiment. 3. Cholesterol in both exposed groups showed increases for the first 15 days and decreases at day 21. 4. Different time evolution in the control and in the treated group was observed. 5. Plasma sodium only showed a significant decrease ( p < 0.001) from 1 to 7–15 days of copper exposure.

Effect of Copper on the interaction between the PredatorDidinium nasutumand its PreyParamecium caudatum

Tests to determine acute copper toxicity levels demonstrated that the protozoan predator Didinium nasutum were more susceptible to copper stress than its prey Paramecium caudatum Thus we predicted that Paramecium and Didinium densities, at the equilibrium point of their interaction, would be higher at sublethal copper levels due to a decrease in the predator's efficiency. This situation is likely to produce a decrease in the stability of the system. However, isocline analysis did not support the predictions based on the acute lethality tests. Equilibrium densities of both predator and prey did not change at copper levels between 30 and 180 μg/L. The mathematical analysis suggested that the interaction became less stable with increasing copper concentrations. However, stability decreased due to hormesis in Didinium at sublethal copper levels and not due to a reduction in predator efficiency as expected. At 300 μg Cu/L, densities of both species at equilibrium were higher and the stability of the system decreased. This decrease in stability resulted from a reduction in predator efficiency, as 300 μg Cu/L is not sublethal for Didinium.

Increased Susceptibility of Rainbow Trout to Infectious Hematopoietic Necrosis Virus After Exposure to Copper

Exposure of rainbow trout to sublethal levels of copper in water increased their susceptibility to infectious hematopoietic necrosis virus. In most instances, the percent mortality was twice as great in the stressed groups compared with those groups which were not stressed but received the same virus dose. Although the level of copper in the water influenced the mortality rates, the length of exposure did not prove to be critical, as similar results were obtained after 1, 3, 5, 7, or 9 days of exposure. When different virus challenges were employed, the percent mortalities were again greater in the stressed fish at all virus doses tested, and at one dose level mortalities were noted in the stressed group but not in the untreated group.