Abstract
Due to anthropogenic activities, heavy metals still represent a threat for various trophic levels. If aquatic animals are exposed to heavy metals, we can obviously observe considerable toxicity. It is well known that organisms treated with heavy metals synthesize low molecular mass compounds rich in cysteine. In this work the effects of cadmium chloride (2.5, 5, 7.5, 10 and 12.5 mg/L) on common carp (Cyprinus carpio) was investigated. We determined cadmium content in tissue of muscle, liver and kidney by atomic absorption spectrometry with electrothermal atomization and content of metallothionein (MT) in the same tissues by the Brdicka reaction. Electrochemical methods can be considered as suitable and sensitive tools for MT determination in carp tissues. Results of our study showed a gradually enhancing of cadmium content in muscle with time and dose of cadmium chloride in water. MT levels in liver reached both high levels (above 130 ng/g) in fish exposed to 2.5, 5 and 7.5 mg/L and low level (to 50 ng/g) in fish exposed to 10 and 12.5 mg/L of cadmium chloride. This finding confirms that the synthesis of metallothioneins and binding capacity of these proteins is restricted.
Highlights
Cadmium (Cd) belongs to the group of highly toxic heavy metals
Liver and kidney and MT in liver and kidney in fish groups exposed to different concentration of cadmium chloride for a specific period were compared by mean of KruskalWallis test, followed by multiple comparison
Cadmium content in muscle differed significantly among fish groups exposed to different concentrations of cadmium chloride for 24, 48 and 72 hours, as well as for 96 hours (Kruskal-Wallis test: comparison of fish groups exposed for 24 hours: P < 0.001; comparison of fish groups exposed for 48 hours: P < 0.01; comparison of fish groups exposed for 72 hours: P = 0.05; comparison of fish groups exposed for 96 hours: P = 0.01)
Summary
Cadmium (Cd) belongs to the group of highly toxic heavy metals. Naturally, it occurs in water only in trace amounts, but recently its levels have increased due to anthropogenic activities [1]. Most cadmium contamination comes from metal foundries, the dye industry, production of plastics and of accumulators This exposure results in pathological changes in water ecosystems, mostly demonstrated in fishes, which are affected by heavy metals through the respiratory and digestive systems and through the skin. It was discovered that organisms protect themselves against the toxic effect of metals by synthesis of extra proteins called metallothioneins (MTs), which are abundant throughout the whole animal kingdom [3]. These proteins are rich in cysteine and are able to bind metal ions [4]. The influence of cadmium chloride in water on levels of cadmium in muscles, liver and kidneys and to levels of metallothioneins in these tissues of fish was studied
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