Subcellular Distribution Of Metals Research Articles

Relationship between Subcellular Cadmium Distribution in Prey and Cadmium Trophic Transfer to a Predator

We tested the hypothesis that exposure-related alterations in the subcellular Cd distribution in prey relate to changes in Cd absorption by a predator. Oligochaete worms,Limnodrilus hoffmeisteri were exposed for 1 wk or 6 wk to 0.5 μg Cd 1−1, 47 μg Cd 1−1, or 140 μg Cd 1−1 (including109Cd as a tracer) and relationships between oligochaete subcellular Cd distribution and Cd absorption by a predator, the grass shrimp (Palaemonetes pugio), were determined. Concentration and duration of Cd exposure had direct effects on oligochaete subcellular Cd distribution. Changes in oligochaete subcellular Cd distribution were characterized by increases in both the amount and proportion of Cd bound to the cytosolic fraction. The induction of Cd-binding proteins (e.g., metallothioneins) were suspected to be responsible for these changes. We found 1∶1 relationships between the amount and percentage of Cd in oligochaete cytosol and the amount and percentage of Cd adsorbed by shrimp. These results demonstrate that only metal bound to the soluble fraction of prey is available to higher trophic levels, and that factors influencing subcellular metal distribution in prey will directly alter metal trophic transfer to predators.

Accumulation and subcellular distribution of metals (Cu, Fe, Mn, Pb and Zn) in the Mediterranean mussel Mytilus galloprovincialis during a field transplant experiment

Marine mussels are generally used as biomonitors of heavy metal pollution in coastal areas. However, the time-integration capacity of these molluscs may vary from different metals and this fact should be considered when interpreting heavy metal concentrations in natural mussel populations. The aim of this work was to investigate the uptake-excretion kinetics and the subcellular distribution of metals in field conditions: the results were expected to provide useful information on the different time-integration capacities of mussels for various elements. Mussels from a clean site were transplanted to a heavy metal polluted environment where they accumulated Pb, Fe, and Mn. The accumulation was not linear but a steady state was reached after only 2 weeks, indicating that mussels can rapidly equilibrate with enhanced environmental levels of these pollutants. Copper and zinc were not accumulated by transplanted mussels, suggesting a similar bioavailability in the two environments or a certain regulation capability of molluscs for these essential elements. Polluted mussels, allowed to depurate in clean seawater, showed excretion rates which were different between elements. Moreover the subcellular distribution was characteristic for each metal but the patterns were similar in wild populations as well as in transplanted and depurating mussels, indicating that the same subcellular fractions are involved in the uptake, storage and excretion of metals. From the results, the different time-integration capacities of mussels for various elements appear to be related to the cellular mechanisms involved in their detoxification and/or excretion.

Cadmium accumulation in organs of the scallop Mizuhopecten yessoensis—II. Subcellular distribution of metals and metal-binding proteins

1. Cd accumulation in the hepatopancreas and gills of the scallop resulted in an increase of metal concentration in the cytoplasm, while in control animals the general amount of Cd in the hepatopancreas was concentrated in the microsomes and cytoplasm. 2. Cd appears to be equally distributed among high molecular weight proteins and metallothioneins in control animals. 3. It was shown that during the experiment the metal was bound mainly to high molecular weight proteins. 4. After 30 days of exposure of scallops to flowing water Cd was redistributed to metallothioncin (MT)-like proteins. 5. Cd concentration in the lipids of the hepatopancreas of control and experimental scallops was equal.

Subcellular distribution of heavy metals in liver and kidney of a narwhal whale ( Monodon monoceros): An evaluation for the presence of metallothionein

1. The subcellular distribution of Zn, Cd, Cu and Hg in liver and kidney from a narwhal was determined by ultracentrifugation and gel filtration. 2. Most of the total mercury in the liver and kidney was bound by the cellular pellet (88 and 73%, respectively). Of the total mercury, 7 and 11% was in the form of methylmercury in the liver and kidney, respectively. 3. More than half (74%) of the total Zn and Cu in the kidney was in the cytosol and somewhat less than this was in the cytosol of the liver. 4. Almost all of the cadmium in liver and kidney (88 and 92%, respectively) was in the cytosol. 5. Cytosolic fractions from liver and kidney were evaluated for the presence of metallothionein by analysing for Zn, Cd, Hg, Cu, Fe and —SH groups, by molecular weight estimation and by u.v. absorption spectra. Metallothionein was found in these organs in estimated concentrations similar to those present in terrestrial and other marine mammals.

Subcellular distribution of trace metals in the normal and in the copper treated human secretory endometrium

The subcellular distribution of some metals has been studied in the normal human secretory endometrium and in the secretory endometrium of women wearing a copper-T intrauterine device. The sustained release of copper inside the uterine cavity induces some significant changes in the metal composition of this tissue; Mg, Ca and Cu increase while Zn decreases. Neither Na nor K concentrations show any significant change. Under these conditions, endometrial nuclei concentrations seem to be able to passively come to equilibrium with the tissue concentrations of the elements studied, showing only a significant retention of Ca. On the contrary, mitochondria show differential concentrations of all metals. Ca is retained, but all the other elements remain at low levels. Copper is significantly increased in all fractions, but the relative increase is particularly noticeable in the microsomes (6 x). Zinc tends to decrease in all fractions but reaches statistical significance only in the microsomes and the supernatant. These results are analyzed in relation to the mechanism of action of the Cu-T.

Subcellular distribution of metals (sodium, potassium, calcium and magnesium) in rat liver, kidney and intestinal mucosa

1. 1. The subcellular distribution of sodium, potassium, calcium and magnesium has been investigated in rat tissues. 2. 2. Any one metal was usually distributed very similarly between the corresponding fractions in the three tissues examined. 3. 3. The supernatant contained 73–85 per cent of the total sodium and potassium but only 23–42 per cent of the calcium and magnesium. Appreciable proportions of the divalent metals were present in both nuclear, mitochondrial and microsomal fractions. 4. 4. The concentrations of potassium, calcium and magnesium were considerably higher in intestinal mucosa than in liver or kidney. 5. 5. Potential sources of error were investigated and it is concluded that the results are likely to indicate the distribution in the intact cell.

The Effect of Carbon Tetrachloride Poisoning on Subcellular Metal Distribution in Rat Liver

The Effect of Carbon Tetrachloride Poisoning on Subcellular Metal Distribution in Rat Liver