Bioaccumulation of metals and induction of metallothioneins in selected tissues of common carp (Cyprinus carpio L.) co-exposed to cadmium, mercury and lead

Abstract

The concentrations of mercury (Hg), cadmium (Cd) and lead (Pb) at various exposure periods were determined in the gill, kidney, liver and muscle of common carp (Cyprinus carpio L.) co-exposed to 1.0 μg ml-1 each of Cd2+, Hg2+ and Pb2+ for up to 10 days. Metallothionein fractions (MTs) in these organs were characterized using the hyphenated technique of size-exclusion chromatography (SEC) and inductively coupled plasma mass spectrometry (ICF-MS). After 10 days of exposure, maximum toxic metal concentrations of Hg, Cd and Pb were 10.7 (gill), 0.145 (kidney) and 0.112 μg g-1dry weight (gill), respectively. The pattern of accumulation of Hg and Pb was in the order gill > kidney > liver > muscle. In the case of Cd, accumulation was in the order kidney > gill > liver > muscle. Cd and Hg binding MTs were significantly induced in the gill, kidney and liver of all the exposure groups in comparison with the control group (p < 0.05), and the amounts of them increased with the longer exposure time. Despite the higher intracellular Hg concentration and the stronger Hg-SH binding affinity, the amount of Cd-binding MTs was much higher than that of Hg-binding MTs. The results indicate that MT synthesis in these organs was clearly metal-specific. MTs in gill may be used as a bio-marker to detect the metal pollution caused by Hg and Cd. Zinc and copper binding MTs in the organs of the exposed fish were also increased. This may be due to the MTs' important role in the homeostatic regulation of essential metals and their protective role against the acute toxicity of non-essential metals. Even though there was considerable accumulation of lead in the organs of the exposed fish, Pb-binding MT synthesis was non-significant. Copyright © 2006 John Wiley & Sons, Ltd.