Metallothionein levels in liver and kidney of Canadians--a potential indicator of environmental exposure to cadmium

Liver and kidney cortex samples were obtained from 89 human autopsies for the determination of metallothionein (MT), cadmium (Cd), zinc (Zn), and copper (Cu). An age-dependent increase of Cd, Zn, and Cd/Zn was observed in the kidney; increases peaked at mid-age and were followed by a decline. Cadmium was present at a low constant level in the liver at all ages. The mean concentrations of Cd and Zn were 18.0 and 40.1 micrograms/g wet weight, respectively, in the kidney, and for the liver the values for Cd and Zn were 2.0 and 79.0 micrograms/g wet weight, respectively. A positive linear relationship was observed between Cd or Zn and MT in the kidney and between Zn and MT in the liver. No other correlation was found between Cu and MT in either organs. Similar values were obtained for MT when estimated by Ag-hem and Cd-hem methods.     

Induction and metal speciation of metallothionein in wood mice (Apodemus sylvaticus) along a metal pollution gradient

We investigated the binding of Cd, Cu, and Zn to metallothionein (MT) and other metal-binding proteins in free-living wood mice (Apodemus sylvaticus L.) captured in four areas along a metal pollution gradient. We measured total and cytosolic Cd, Cu, and Zn concentrations in mouse liver and kidney by means of inductively coupled plasma-mass spectrometry (ICP-MS). Total (Cu, Cd, Zn)-MT levels were determined in the same tissues by means of the cadmium thiomolybdate saturation assay. Metal speciation of metalloproteins was studied by means of size-exclusion high-performance liquid chromatography-ICP-MS. Liver and kidney of wood mice from the site adjacent to the pollution source showed the highest Cd and Zn concentrations (total and cytosolic) and (Cu, Cd, Zn)-MT levels compared to the other sites farther away from the pollution source. No or only small site differences in tissue Cu concentrations were observed. Almost all the variation (85-95%) in hepatic and renal (Cu, Cd, Zn)-MT levels was explained by the total or cytosolic hepatic Zn and Cd concentration or the renal Cd concentration, respectively. An analysis of the cytosolic metal speciation showed that the Cd-MT, Cu-MT, and Zn-MT fractions in liver and kidney increased significantly with increasing cytosolic metal concentrations. Metals associated with the other cytosolic protein fractions did not increase with increasing exposure. These results illustrate the important role of MT in metal homeostasis and detoxification processes. We conclude that MT is a useful biomarker for environmental metal contamination in free-living wood mice.     

Hepatic Metal and Metallothionein Levels in a Potential Sentinel Teleost,Dulesauriga, from a Southeastern Brazilian Estuary

The identification of estuarine sentinel species is of paramount importance. The potential of the species Dules auriga sampled from Guanabara Bay, Brazil regarding metal contamination was assessed. Hepatic metallothionein (MT) and Fe, Zn, Cu, Mn, Cd and Ag concentrations were determined in cytosolic fractions (S50 and HT S50) by polarography and ICP-OES, respectively. HT S50 Fe, Mn and Zn were lower than in the S50 fraction, indicating MT-detoxification. MT was correlated to HT S50 Zn, indicating Zn homeostasis. Zn was negatively correlated to weight (TW) and length (TL), suggesting environmental Zn influence. A moderate negative correlation between HT S50 Cu and the condition factor (CF) was observed, indicating that increasing environmental Cu concentrations may decrease D. auriga CF. Several inter-elemental correlations were observed. No MT, TW and TL correlations were found. Thus, MT variability is probably linked to environmental metal concentrations. D. auriga fulfills most sentinel requisites, and MT may be an adequate metal contamination biomarker in this species.

     

Metal and metallothionein concentrations in Scoter (Melanitta spp.) from the Pacific northwest of Canada, 1989-1994

Eighty-six surf ( Melanitta perspicillata) and nine white winged (M. fusca) scoters were collected from 1989-1994 at 11 locations in British Columbia and the Yukon. Their kidney and liver tissues were analyzed for cadmium (Cd), copper (Cu), zinc (Zn), and metallothionein (MT) concentrations. Individual kidney Cd values ranged from 2.4 microg/g dry weight (DW) in birds from northern Vancouver Island to 390.2 microg/g (DW) in birds from the Queen Charlotte Islands, which is in the range of values potentially associated with kidney damage. Birds from the Queen Charlotte Islands also had high kidney Zn concentrations, which were significantly higher than values in birds from Naniamo and Westham Island on the south coast of BC. Cd values were significantly (p < 0.001) correlated with both Zn and MT concentrations in kidney tissue (r = 0.66 and 0.62, respectively). Male surf scoters had significantly higher kidney Cd and Zn levels than females, with mean Cd values of 47.3 and 19.7 microg/g DW (p < 0.002) for males and females, respectively. Mean Zn values were 120.8 and 108.0 microg/g DW (p < 0.05) for males and females, respectively. However, no sex differences were observed for either Cu or MT concentrations in kidney tissue. Individual MT values ranged from 2.7 to 416.8 microg/g wet weight (WW). Individual kidney Cu values ranged from 15.1 to 48.4 microg/g DW for both sexes. Kidney and liver Cd concentrations were significantly correlated (r = 0.90, p < 0.05) with kidney levels almost always higher than liver values. Although Cd accumulation by the Skidegate scoters was high, comparable tissue Cd values have been documented in other seabirds collected from the same general area, indicating elevated Cd concentrations in marine food chains around the Queen Charlotte Islands (Haida Gwaii) region of the Pacific coast.     

Variations in metallothionein, Zn, Cu, and Fe concentrations and ceruloplasmin activity in pregnant rat dams and their fetuses

Growing rat fetuses have great need for Zn, Cu, and Fe. In fetal livers (FL) large accumulations of Zn and Cu connected with increased metallothionein (MT) synthesis take place. In dams, serum changes in metals concentrations with increased ceruloplasmin (Cp) activity are observed. The aim of this study was to determine (1) mutual relationships in the accumulation of MT, Zn, Cu, and Fe in fetal livers; (2) changes in Zn, Cu, and Fe concentrations in dam serum; and (3) the day with the maximum Cp activity. Sections of rat dams were taken on 16th-21st day of gestation, twice a day, and MT, Zn, Cu, and Fe concentrations in liver, spleen, kidneys, and placenta of dams and in liver and brain in fetuses were determined. In fetal livers high correlations between MT and Zn and between Zn and Cu were obtained. The investigated Cp activity was always high, reaching its maximum on the 20th day and minimum on the 21st day. Significant correlation between Cp activity and Cu concentration in dam serum was also revealed. In conclusion it is suggested that Zn accumulation in FL is strictly connected with MT synthesis but Cu content in FL is rather dependent on Cp activity in dam serum. Iron accumulation in fetal livers is connected with the diminution of iron concentrations in dam serum.     

Variation of metallothionein and metal concentrations in the digestive gland of the clam Ruditapes decussatus: sex and seasonal effects

Metallothionein (MT) and metal (Cd, Cu, and Zn) concentrations were determined in the digestive gland of male and female Ruditapes decussatus. Clams were collected monthly during the period of sexual development, from June to September, at two different sites of a coastal lagoon, the Ria Formosa Lagoon, on the south coast of Portugal. The MT concentrations were determined in the heat-treated cytosolic fraction of the digestive gland of both male and female clams. Total metal (Cd, Cu, and Zn) concentrations in the heat-treated cytosol of the digestive gland were also determined in both sexes. The MT and metal concentrations in the digestive gland were not sex dependent in this species. Therefore, these results suggest that random samples can be used to determine MT and metal concentrations in the digestive gland of R. decussatus. Seasonal and site-specific dependency, however, were detected for MT, Cd, and Cu concentrations. The maximum concentration levels of MT, Cd, and Cu were detected in July and August for both sexes in the same area. Zinc concentrations, however, did not show marked seasonal variations, indicating that this species is able to regulate zinc concentrations. The highest MT concentrations were significantly related to the highest metal concentrations.     

Comparative study of effect of acute administration of cadmium and silver on ceruloplasmin and metallothionein: Involvement of disposition of copper,iron, and zinc

Male ICR mice were subcutaneously injected with either aqueous Ag (1.5 or 5.0 mg/kg) or Cd (1.5 or 2.5 mg/kg) for 2 consecutive days. Body fluids and livers were collected 24 hr after the second dose. In the hepatic supernatant, Ag and Cd were recovered at 2 and 36–46% of the total dose, respectively. Ag-metallothionein (MT), which is associated with Ag, Cu, and Zn, and Cd-MT, which is associated with Cd, Cu, and Zn, were induced in the liver by the injection of Ag and Cd, respectively. The supernatant Ag and Cd existed in the MT fraction at 34–61 and 97% levels, respectively. Cu concentration in the hepatic supernatant was increased by the Ag and Cd injections. The increased Cu was due to the appearance of Ag-MT and Cd-MT, respectively. Microsomal concentrations of Cu increased in the Cd groups, but decreased in the Ag groups. Serum ceruloplasmin (Cp) activity was remarkably increased by the injection of Cd, but severely decreased by the injection of Ag. These opposing changes in Cp activity induced by Cd and Ag may be due not to the sequestering of Cu in MT, but to the alteration of microsomal Cu concentration and/or the difference in affinity of the induction metals to MT. Hepatic Fe concentration was increased by the Ag injection, but was decreased by the Cd injection. These changes may not be related to induction of MT, but to Cp synthesis in the liver.     

Concentrations and correlations for eight metals in human liver

This study was undertaken to determine concentrations for eight metals in human liver and investigate correlations among these metals as well as subject age. Autopsy specimens from 32 males, ranging from 38–88 years of age, were analyzed for calcium (Ca), cadmium (Cd), copper (Cu), iron (Fe), mercury (Hg), magnesium (Mg), lead (Pb), and zinc (Zn). Respective mean concentrations were 49.6, 2.1, 4.9, 318.7, 0.72, 135.2, 0.19, and 53.4 μg/g wet wt., and 209.2, 8.8, 20.6, 1342.2, 0.81, 569.4, 3.1 and 228.8 μg/g dry wt. Variables, including age and metal concentrations, were subjected to simple and multiple correlation analysis. Four metal pairs Zn-Cd, Fe-Pb, Mg-Hg, and Mg-Zn gave significant positive correlations. Age and Cu correlated negatively. Multiple correlations were found for Mg with Hg and Zn, Pb with Fe and age, Pb with Fe and Cu, and Zn with Mg and Cd. Results are discussed within the context of relevant literature.     

Environmental Cd and Zn Concentrations in Liver and Kidney of European Hare from Different Serbian Regions: Age and Tissue Differences

A total of 84 European hares collected from eleven Serbian regions investigated upon cadmium (Cd) and zinc (Zn) presence. Strong statistically significant correlations between Cd concentrations in kidney and liver were registered in animals older than 12 months. Significant differences between Zn concentrations in liver in comparison to kidney were found within every single age group with exception of the oldest. Negative correlation (Ps—Pearson’s correlation) between Zn and Cd concentrations were found in liver samples within the age group of 12 months (Ps = ?0.67, p = 0.004).     

Correlation of MT Levels in Livers and Gills with Heavy Metals in Wild Tilapia (Oreochromis mossambicus) from the Klang River,Malaysia

Metallothionein (MT) concentrations in gill and liver tissues of Oreochromis mossambicus were determined to assess biological response of fish to levels of some metals. Metal concentrations in gill and liver tissues of O. mossambicus ranged from 0.6 to 2.6 for Cd, 16 to 52 for Zn, 0.5 to 17 for Cu and 2 to 67 for T–Hg (all in μg/g wet weight, except for T–Hg in ng/g wet weight). Accumulation of Cd, Zn, Cu and Hg (μg/g wet weight) in the liver and gills of O. mossambicus were in the order of liver > gills. The concentrations of Cd, Zn, Cu and Hg in fish tissues were correlated with MT content. The increases in MT levels from the reference area Puchong Tengah compared to the polluted area Kampung Seri Kenangan were 3.4- and 3.8-fold for gills and livers, respectively. The results indicate that MT concentrations were tissue-specific, with the highest levels in the liver. Therefore, the liver can act as a tissue indicator in O. mossambicus in the study area.     

Metal and Metallothionein Concentrations in Scoter (Melanitta spp.) from the Pacific Northwest of Canada, 1989–1994

Eighty-six surf (Melanitta perspicillata) and nine white winged (M. fusca) scoters were collected from 1989–1994 at 11 locations in British Columbia and the Yukon. Their kidney and liver tissues were analyzed for cadmium (Cd), copper (Cu), zinc (Zn), and metallothionein (MT) concentrations. Individual kidney Cd values ranged from 2.4 μg/g dry weight (DW) in birds from northern Vancouver Island to 390.2 μg/g (DW) in birds from the Queen Charlotte Islands, which is in the range of values potentially associated with kidney damage. Birds from the Queen Charlotte Islands also had high kidney Zn concentrations, which were significantly higher than values in birds from Naniamo and Westham Island on the south coast of BC. Cd values were significantly (p < 0.001) correlated with both Zn and MT concentrations in kidney tissue (r = 0.66 and 0.62, respectively). Male surf scoters had significantly higher kidney Cd and Zn levels than females, with mean Cd values of 47.3 and 19.7 μg/g DW (p < 0.002) for males and females, respectively. Mean Zn values were 120.8 and 108.0 μg/g DW (p < 0.05) for males and females, respectively. However, no sex differences were observed for either Cu or MT concentrations in kidney tissue. Individual MT values ranged from 2.7 to 416.8 μg/g wet weight (WW). Individual kidney Cu values ranged from 15.1 to 48.4 μg/g DW for both sexes. Kidney and liver Cd concentrations were significantly correlated (r = 0.90, p < 0.05) with kidney levels almost always higher than liver values. Although Cd accumulation by the Skidegate scoters was high, comparable tissue Cd values have been documented in other seabirds collected from the same general area, indicating elevated Cd concentrations in marine food chains around the Queen Charlotte Islands (Haida Gwaii) region of the Pacific coast. Received: 17 January 2002/Accepted: 2 June 2002     

Variation of metal and metallothionein concentrations in a natural population of Ruditapes decussatus

The spatial and seasonal variation of total and subcellular distribution of Cd, Cu, and Zn was followed in different tissues (gills, digestive gland, and remaining tissues) of the clam Ruditapes decussatus collected along a metal contamination gradient in the Ria Formosa lagoon (southern Portugal) and compared with metallothionein (MT) concentrations.Total metal concentrations decreased according to the sequence digestive gland > gills > remaining tissues for Cd, digestive gland approximately gills > remaining tissues for Cu and gills > digestive gland > remaining tissues for Zn. MT concentrations in these tissues decreased according to the same sequence observed for Cd. In all the tissues, the highest subcellular concentration was in the cytosol for Cd and Cu and in the pellet for Zn. Among the three metals, Cd concentrations showed the most evident spatial variation. In all tissues, total and subcellular Cd concentrations decreased from the inner parts of the lagoon toward the ocean. However, no significant spatial or seasonal variation occurred in clam tissues for the other two metals, though marginal elevated Cu concentrations were observed in the inner parts of the lagoon. Therefore, Cu subcellular distribution in clam tissues was not significantly altered by Cu changes in the lagoon and are the baseline levels for normal metabolism of this clam population. The fact that total Zn concentrations remained unchanged both spatial and seasonal suggested that these clams regulate Zn in their tissues.In the three tissues, MT bind most significantly to Cd and Cu, while Zn, although binding to MT, is preferably bound to other ligands. MT concentrations showed the same spatial and seasonal variation of Cd and were significantly related with total and heat-treated cytosolic Cd in all tissues. For Cu a significant relationship between MT and total or cytosolic Cu was only observed in the remaining tissues. No relationship was observed between MT and total or cytosolic Zn concentrations. Metals and MT concentrations increased with the increase in the condition index for the gills and the digestive gland and decreased from the remaining tissues.Cd concentrations in the gills increased only in the heat-treated cytosolic fraction while Zn in this fraction decreased. Thus Cd concentrations in this tissue displaced Zn from the MT-fraction, leading to a modification of the soluble/insoluble Zn ratio once total Zn concentrations remained unchanged. This modification reflects a perturbation in the normal metabolism in this tissue due to the excess of Cd present. With the exception of the gills, Zn subcellular distribution in the other two tissues was similar among sites and season.The model that describes the relationship between MT, metals, and weight in the gills, digestive gland and remaining tissues also indicates that Cd was the only metal that influence MT synthesis significantly in all the tissues. The induced and/or existent MT was sufficient to bind free Cd ions present in the cells, preventing any damage to cellular metabolism in this clam population. Therefore, MT in the gills and digestive gland of R. decussatus can be used as an early warning signal for Cd exposure and are a useful biomarker to assess the toxicological status of this population in the Ria Formosa lagoon.     

Trace element and metallothionein concentrations in seabirds from the Canadian Arctic

Livers and kidneys were collected for five seabird species from the Canadian Arctic during the 1983 and 1991 to 1993 breeding seasons. Livers were analyzed for Cd, Hg, Pb, and Se, and kidneys were analyzed for Cd, Cu, Zn, and metallothionein (MT). Concentrations of the essential elements, Cu and Zn, were in agreement with those previously published in the literature. Thick-billed murres (Uria lomvia) from Ivujivik on the Hudson Strait/Hudson Bay coast in northwestern Quebec (Canada) had the highest mean renal concentrations of Cu, Zn, and Cd. Among the four species collected from Prince Leopold Island, northern fulmars (Fulmarus glacialis) had the highest hepatic concentrations of both Cd and Hg. The highest Se concentrations were found in northern fulmars and black-legged kittiwakes (Rissa tridactyla) from Prince Leopold Island. Hepatic Pb concentrations were low (<0.3 microg/g dry wt) in all species at all locations. Metallothionein concentrations were positively correlated with Cd and Zn for all species combined but were not correlated with Cu in any species. No significant relationships were found between MT and Cu or Zn in black guillemots (Cepphus grylle) or glaucous gulls (Larus hyperboreus). To our knowledge, this is the first report of MT concentrations and their relationships with trace metals in Arctic seabirds.     

Metallothionein concentrations in natural populations of gudgeon (Gobio gobio): relationship with metal concentrations in tissues and environment

A field monitoring campaign investigating the suitability of (Cd, Zn)-metallothionein concentrations (MTs) in different tissues of the gudgeon as a biomarker for metal contamination in the aquatic environment was conducted. Gudgeons were captured at 10 sampling sites on a river system in Flanders (Belgium). Nine sampling sites were situated along a Cd and Zn gradient with a nearby tributary as the reference site. Cadmium, Cu, and Zn concentrations were measured in the water and sediments. Concentrations of (Cd, Zn)-MT were measured in different organs (gill, liver, kidney) of gudgeon (Gobio gobio). The hepatic and gill Cd and Zn concentrations, as well as the hepatic (Cd, Zn)-MT concentrations, reflected the polymetallic contamination gradient. Moreover, the hepatic Cd and Zn concentrations could describe 72% of the variance in the (Cd, Zn)-MT concentrations in the liver, illustrating the possible use of hepatic MT concentrations as a biomarker for environmental metal contamination. In this way a dose-response relationship could be established under natural conditions. However, a poor negative relation between the Cd and Zn concentrations in the gills and the corresponding (Cd, Zn)-MT concentrations was found. No relation between the Cd and Zn concentrations in the kidney tissue and the corresponding (Cd, Zn)-MT concentrations could be established. These results clearly illustrate the tissue-specificity of the MT concentrations, thus for monitoring purposes MT concentrations should be measured in liver tissues, rather than in kidney or gill tissues.     

The relationship of the increased level of metallothionein with heavy metal levels in the tissue of the harbor seal (Phoca vitulina)

The relationship between age, heavy metal levels, and a heavy-metal binding protein, metallothionein (MT), in the liver and kidney of the harbor seal (Phoca vitulina) was studied. The cadmium (Cd) level in the liver and the Cd, inorganic mercury (I-Hg), and zinc (Zn) levels in the kidney were increased with body length, suggesting an age-related accumulation of these metals. The MT levels determined by an MT radioimmunoassay showed concentrations of 240 +/- 139 micrograms/g in the liver and 343 +/- 219 micrograms/g in the kidney. These MT levels were shown to be correlated with age. The statistically significant relationship of the MT levels with the levels of Cd and Zn in the liver and those of Cd, Zn, and I-Hg in the kidney suggested that the protein is responsible for the sequestration of these metals as already observed in terrestrial animals.     

Effect of zinc deficiency on the accumulation of metallothionein and cadmium in the rat liver and kidney

The effects of zinc (Zn) deficiency and repeated exposure to cadmium (Cd) on the accumulation and distribution of metallothionein (MT), Cd and Zn in the liver and kidney were studied. Male Sprague-Dawley rats were fed either a Zn-deficient (1 ppm) or a Zn-adequate (40 ppm) diet during the experiment, and the rats were injected subcutaneously with a cadmium chloride solution (1.0 mg Cd/kg of body weight, 5 days a week) for 4 weeks. Cadmium, Zn, and Cd-induced MT concentrations in the liver and kidney were lower in the Zn-deficient rats (–Zn + Cd) than in the Zn-adequate rats (+ Zn + Cd), while the content of Cd bound to high molecular weight proteins (HMWP) was greater in the Zn-deficient rats (–Zn + Cd). The Zn bound to Cd-induced MT was reduced to 30% in the liver and to 60% in the kidney of the Zn-deficient rats (–Zn + Cd) as compared with that of the Zn-adequate rats (+ Zn + Cd). In the kidney of Zn-deficient rats, exposure to Cd caused a decrease in essential Zn associated with HMWP as compared with that of Zn-adequate rats (+ Zn + Cd). Thus, Zn-deficiency affected the distribution of Cd in tissues, MT and HMWP and accelerated substantially Cd-induced Zn-deficiency in the kidney. Although the renal Cd concentration was lower in the Zn-deficient rats (–Zn + Cd) than in the Zn-adequate rats (+ Zn + Cd), exposure to Cd for four weeks resulted in glucosuria and an increase in liver and kidney weights in the Zn-deficient rats (–Zn + Cd), but not in the Zn-adequate rats (+ Zn + Cd). These results suggest that development of Cd toxicity is related to the Zn status of the body, to the accumulation of Cd in HMWP and to the amount of essential Zn associated with HMWP.     

Variation of Metal and Metallothionein Concentrations in a Natural Population of <Emphasis Type="Italic">Ruditapes decussatus</Emphasis>

The spatial and seasonal variation of total and subcellular distribution of Cd, Cu, and Zn was followed in different tissues (gills, digestive gland, and remaining tissues) of the clam Ruditapes decussatus collected along a metal contamination gradient in the Ria Formosa lagoon (southern Portugal) and compared with metallothionein (MT) concentrations. Total metal concentrations decreased according to the sequence digestive gland > gills > remaining tissues for Cd, digestive gland ≈ gills > remaining tissues for Cu and gills > digestive gland > remaining tissues for Zn. MT concentrations in these tissues decreased according to the same sequence observed for Cd. In all the tissues, the highest subcellular concentration was in the cytosol for Cd and Cu and in the pellet for Zn. Among the three metals, Cd concentrations showed the most evident spatial variation. In all tissues, total and subcellular Cd concentrations decreased from the inner parts of the lagoon toward the ocean. However, no significant spatial or seasonal variation occurred in clam tissues for the other two metals, though marginal elevated Cu concentrations were observed in the inner parts of the lagoon. Therefore, Cu subcellular distribution in clam tissues was not significantly altered by Cu changes in the lagoon and are the baseline levels for normal metabolism of this clam population. The fact that total Zn concentrations remained unchanged both spatial and seasonal suggested that these clams regulate Zn in their tissues. In the three tissues, MT bind most significantly to Cd and Cu, while Zn, although binding to MT, is preferably bound to other ligands. MT concentrations showed the same spatial and seasonal variation of Cd and were significantly related with total and heat-treated cytosolic Cd in all tissues. For Cu a significant relationship between MT and total or cytosolic Cu was only observed in the remaining tissues. No relationship was observed between MT and total or cytosolic Zn concentrations. Metals and MT concentrations increased with the increase in the condition index for the gills and the digestive gland and decreased from the remaining tissues. Cd concentrations in the gills increased only in the heat-treated cytosolic fraction while Zn in this fraction decreased. Thus Cd concentrations in this tissue displaced Zn from the MT-fraction, leading to a modification of the soluble/insoluble Zn ratio once total Zn concentrations remained unchanged. This modification reflects a perturbation in the normal metabolism in this tissue due to the excess of Cd present. With the exception of the gills, Zn subcellular distribution in the other two tissues was similar among sites and season. The model that describes the relationship between MT, metals, and weight in the gills, digestive gland and remaining tissues also indicates that Cd was the only metal that influence MT synthesis significantly in all the tissues. The induced and/or existent MT was sufficient to bind free Cd ions present in the cells, preventing any damage to cellular metabolism in this clam population. Therefore, MT in the gills and digestive gland of R. decussatus can be used as an early warning signal for Cd exposure and are a useful biomarker to assess the toxicological status of this population in the Ria Formosa lagoon. Received: 31 January 2002/Accepted: 29 July 2002     

Cadmium,Copper, Lead and Zinc Concentrations in Female and Embryonic Pacific Sharpnose Shark (Rhizoprionodon longurio) Tissues

In this work we compared the cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) contents of muscle, liver and placenta of gestating females of the viviparous shark Rhizoprionodon longurio and of muscle, liver and umbilical cord of their respective embryos. The higher values of the essential Cu and Zn were in embryonic or embryo-related tissues (placenta and umbilical cord). Maternal muscle and liver had the highest values of Pb and Cd, respectively. There were significant direct correlations between the Zn and Cd concentrations of placenta and umbilical cord, as well as between maternal muscle and embryonic livers for Pb and Cd, but the relation between these tissues was inverse in the case of Zn. All correlations between the metal content of embryonic tissues and size of the embryos were negative, suggesting an inverse relation between the rate of mother-to-embryo metal transfer and embryonic growth.     

Cadmium turnover and changes of zinc and copper body status of rats continuously exposed to cadmium and ethanol

The effects of continuous exposure to cadmium (Cd) and ethanol on Cd turnover and zinc (Zn) and copper (Cu) body status of male Wistar rats were studied. The animals received an aqueous solution of 10% (w/v) ethanol and/or 50 mg Cd/l as the only drinking fluid for 12 weeks. The concentrations of Zn, Cu and Cd in the serum (or blood), liver, kidneys, spleen, brain, heart, femoral muscle and femur as well as in 24-h urine and faeces specimens were assessed by atomic absorption spectrometry (AAS). Ethanol alone had no effect on Cd accumulation or excretion. By contrast, co-administration of ethanol with Cd influenced the turnover of this toxic metal. Long-term consumption of ethanol alone caused a decrease in femur Zn and liver Cu concentrations. Moreover, the urinary loss of both bioelements decreased, whereas their faecal excretion was increased. Exposure to Cd resulted in an increase in liver and kidney and in a decrease in femur and 24-h urine Zn concentrations. An increase in Cu concentration in the kidney and a decrease in the brain were also noted. Moreover, Cd increased the total pool of Zn in organs (kidneys, liver, spleen, heart and brain), but did not influence that of Cu. Zn concentration in the liver, kidney and spleen of rats co-exposed to Cd and ethanol were increased, but were decreased in the brain and femur, compared to controls. The concentrations of Cu in livers and brains of these rats were decreased, whereas those in kidney, spleen and heart were increased. The urinary excretion of the elements was decreased, whereas their faecal excretion was increased. Moreover, the total amount of Cu in organs decreased below the control value and that of Zn was in the normal range. These changes in Zn and Cu levels could be explained by different effects of both toxic substances, differences in bioelement intakes (due to reduced consumption of drinking solutions and food), and the modifying effect of ethanol on Cd turnover. Our results suggest that alcoholics may be more susceptible to Cd accumulation and its effects on body Zn and Cu.     

Correlation of cadmium-induced nephropathy and the metabolism of endogenous copper and zinc in rats

Female Wistar rats were injected (sc) every second day for 8 weeks with Cd (0.25 mg/kg) as CdCl2. After only a 2-week exposure, when cadmium (Cd) concentration in liver was about 13 micrograms/g, ultrastructural examinations revealed some irregular ergastoplasm systems and significant proliferation of smooth endoplasmic reticulum in the hepatocyte ultrastructure. The increase in Zn content occurred simultaneously with the increase in Cd concentration in the liver (Zn to Cd ratio was 1:1). In the kidneys after a 3-week exposure, when Cd concentration was 7 micrograms/g, the concentration of endogenous Cu increased. At the same time the urinary excretion of that metal was considerably higher than that of the control group. In the kidneys after a 4-week exposure, when Cd concentration in this organ exceeded 10 micrograms/g tissue, injured brush border microvilli and swollen mitochondria in the proximal convoluted tubular cells were seen. In renal corpuscules, fusion between the podocyte pedicles was also found. The changes in renal cortex ultrastructure became more pronounced when Cd concentration in kidney was increasing. Necrotic changes in the examined organ were observed when Cd concentration increased to about 30 micrograms/g tissue. The critical concentration in renal cortex of about 200 micrograms/g tissue should be revised. The present margin of safety with regard to risk of renal effects is small.