Cadmium accumulation and biochemical responses in Sparus aurata following sub-lethal Cd exposure

Cadmium (Cd), a heavy metal with limited biological function, is widely distributed in the aquatic environment as a result of natural and anthropogenic activities. The effect of 4 and 11 days exposure of gilthead sea bream Sparus aurata to sub-lethal concentrations of Cd was evaluated as levels of Cd content and Cd-metallothionein (MT) presence in different organs. The possible genotoxic effect was also evaluated in erythrocytes by using the "comet assay", a promising tool for estimating DNA damage at the single-cell level. The results obtained show that in the controls, Cd content was significantly higher in gills compared to in liver, but the treatment of fish with 0.1mg/l Cd induced a stronger accumulation of metal in liver depending on the length of the exposure period. Cd traces were found in plasma, muscle and kidney. Cd forms complexes in the cytosol with MT only in the liver but Cd-MT content significantly increased after 11 days of exposure to the metal, while after 4 days of treatment the protein level was similar to the control. The "comet assay" performed on S. aurata eryhtrocytes isolated from fish treated for 4 and 11 days with 0.1mg/l Cd, showed that there was no DNA damage at both exposure periods.

Trace metals in arcid clam Scapharca inaequivalvis: effects of molluscan extracts on bioluminescent bacteria

The relationship between a supposed effect of molluscan extracts on bioluminescent bacteria and metal concentrations in the extracts was investigated. For this purpose a biotoxicological assay based on bioluminescent bacteria (BLB) and extracts from metal exposed molluscs, Scapharca inaequivalvis, was optimized to monitor Cd and Cu marine pollution. Cu and Cd concentrations increased in tissues of experimentally exposed molluscs. Molluscan extracts inhibited the bacterial luminescence, the inhibition decreasing as the time of mollusc exposure to metals increased, suggesting a reduction of the "bioactive" metals. In regard to the use of BLB test in environmental monitoring, the analysis of Cu, Cd, and metallothionein (MT) was first performed in tissues from molluscs collected in three different areas of Northern Adriatic Sea. Metal concentrations reached maximum values in the gills, while Cd was mostly bound to MT in the kidney. Significant differences in metals and MT concentrations were found depending on the sampling sites. The biotoxicological assay resulted slightly correlated with the biochemical parameters.

Localization of metallothionein I-II immunoreactivity in bovine pituitary gland

Metallothioneins belong to a family of shock proteins characterized by an unusual high content of cystein, absence of aromatic amino acids and high metal content (Zinc and Copper). Metallothioneins are ubiquitously present in a large variety of prokaryotic and eukaryotic species as well as in all mammalian organs and tissues examined thus far. To the best of our knowledge this is the first report describing the presence of metallothioneins in the pituitary gland. Metallothioneins were identified immunohistochemically and chromatographically both in the neuro and adenohypophysis of the bovine pituitary gland. Metallothioneins are highly expressed in the neurohypophyseal glial cells, and in a subpopulation of folliculo-stellate cells located in the pars intermedia of the adenohypophysis. While the specific role of these proteins in the pituitary gland remains to be established, we hypothesize that, besides their protective action against free radicals, hypophyseal metallothioneins might be involved in the regulation of metal ion homeostasis with putative implication in release of hypothalamic peptide hormones in the neurohypophysis and synthesis/release of alpha-MSH by POMC-cells located in the pars intermedia of the adenohypophysis.

Seasonal dependence of cadmium accumulation and Cd-binding proteins in Mytilus galloprovincialis exposed to cadmium

At different periods of the year specimens of Mytilus galloprovincialis were exposed to 0.5 microg Cd/ml seawater for 7 days. Concentrations of trace elements (Cd, Zn, Cu and Fe) and Cd-binding proteins in gills, viscera, muscle and mantle were determined after 1 weeks exposure. Cadmium accumulation was higher in May and June and was tissue dependent; it was highest in the gills and decreased in the order: gills > viscera > mantle and adductor muscle. Significant seasonal variations of zinc, copper and iron, were also found, in both exposed and control molluscs. The percentage of Cd distribution between cytosol and pellet changed during the year; a clear shift from the particulate fractions to the cytosolic fractions was measured during May and June, especially in the gills. Metallothionein (MT) was the main ligand responsible for Cd accumulation, and this protein reached a maximum between May and June. Inclusion of mercaptoethanol during the purification procedure was found to improve MT isolation by gel chromatography. In the absence of mercaptoethanol, MT showed polymerization patterns which were season dependent and temperature independent, whereas its concentration was increased in mussels kept at higher temperature.

Effects of different levels of dietary zinc on the gilthead, Sparus aurata during the growing season

Gilthead were fed three diets. Diet A was the control diet, whereas diets B and C were supplemented with 300 and 900 mg Zn/kg, respectively. Fish fed with diet C, at the end of the experiment, showed the lowest weight. Zinc concentrations presented the higher values in gills, liver, and kidney. Muscle and brain had the lower mean values and showed a tight control of zinc levels. These results reinforce the hypothesis that zinc in the CNS should be strictly controlled in order to maintain the functional role of the metal. Significant differences in tissue zinc concentrations were obtained between fish fed different amounts of zinc, the metal concentrations being higher in tissues of fish fed diet C. The tissue decrease of zinc, found at the end of the experiment, may depend on a lower feed consumption or on different zinc requirements during the cold season. These changes, even if not univocal among the three diets, may be associated with the life cycle of fish. Furthermore, copper concentrations were little affected by the different concentrations of zinc in the three diets; liver and kidney presented the highest concentrations; liver showed a significant decrease in copper content at the end of the experiment. We conclude that: zinc concentrations of the diet may affect the gilthead weights and the tissual metal content; and zinc concentrations in the diets, depending on the growth rate, may be varied depending on the season.

Cd-metallothionein in liver and kidney of goldfish (Carassius auratus): effects of temperature and salinity

Treatment of goldfish with Cd, by intraperitoneal injection, resulted in Cd-metallothionein (Cd-MT) synthesis mainly in liver and kidney. The relative amount of Cd sequestered by liver metallothionein was always greater in fish maintained at 20 degrees C compared to those reared at 10 degrees C, indicating a temperature dependence of metallothionein biosynthesis; in the kidney this dependence was not so clearly evident. Changes in MT levels induced by adapting fish to different salinities did not correlate with the salinity change.

Isoelectric focusing of lateral muscle myogen and haemoglobins of two species of Mugilidae

1. The myogen protein patterns of lateral muscle of Liza ramada (Risso) and Chelon labrosus (Risso), revealed by isoelectric focusing, are reported. Specific differences are noted both in the white and in the red muscle (where they are more evident). 2. Red muscle shows the presence of a chromoprotein, found to be myoglobin, with a pI characteristic for the species. 3. Blood haemoglobins were examined with the same technique and also found to be species specific.