The influence of cadmium and zinc on cadmium turnover in the zebrafish,Brachydanio rerio

A study was made of the dynamics of non-dietary cadmium in fish exposed to different concentrations of cadmium and zinc in water. Zebrafish,Brachydanio rerio, were exposed to Cd and Zn for various periods. The fate of a short pulse of the radioactive tracer¹⁰⁹Cd (3 or 9 days) was studied during a post-pulse period of 53 or 83 days. The tracer elimination and accumulation were described by exponential equations. The constants obtained from regression analysis of the results were used as a tool for evaluation of the findings.The majority of the¹⁰⁹Cd taken up in the gills during the pulse period was retained in the gill tissue and slowly transferred to the internal organs or lost to the water during the post-pulse period. The retention of tracer in the gills after a 3-day¹⁰⁹Cd pulse was increased by Zn but not influenced by Cd. Continuous exposure to stable Cd increased the rate of turnover of the retained¹⁰⁹Cd. Both Cd and Zn increased the tracer accumulation in the liver and kidney. The results also indicated that the effect of Zn on the Cd turnover might be lost if the environmental Zn is withdrawn before the start of the¹⁰⁹Cd pulse.A tendency of increased mortality of the fish exposed to 1 g Cd/L for 2–3 months suggested that low concentrations of Cd is toxic to the fish during chronic exposure. The increased Cd uptake and transfer in the gills, caused by Zn, could have deleterious effects on the fish. It might also reflect a change in the form of transport and in the intracellular handling of the metal, which protects the fish from Cd toxicity. However, a Zn pre-exposure did not decrease the mortality, which suggests that Zn did not protect the fish from Cd toxicity.     

Metal-metal interactions of dietary cadmium, copper and zinc in rainbow trout, Oncorhynchus mykiss

The influence of metal-metal interactions on uptake, accumulation, plasma transport and chronic toxicity of dietary Cu, Cd and Zn in rainbow trout (Oncorhynchus mykiss) was explored. Juvenile rainbow trout were fed diets supplemented with (μg/g) 500 Cu, 1000 Zn and 500 Cd singly and as a ternary mixture at 2.5% body weight daily ration for 28 days. Complex interactions among the metals dependent on the tissue/organ, metals ratios and duration of exposure were observed. While Zn did not accumulate, whole-body Cd and Cu concentrations increased following linear and saturation patterns, respectively. Early enhanced whole-body Cu accumulation in fish exposed to the metals mixture was correlated with reduced Cd concentration whereas late enhancement of Cd accumulation corresponded with elevated Cd concentration. This suggests early mutual antagonism and late cooperation between Cd and Cu probably due to interactions at temporally variable metal accumulation sites. At the level of uptake, Cd and Cu were either antagonistic or mutually increased the concentrations of each other depending on the duration of exposure and section of the gut. At the level of transport, enhanced Cd accumulation in plasma was closely correlated with reduced concentrations of both Zn and Cu indicating competitive binding to plasma proteins and/or antagonism at uptake sites. Compared to the Cu alone exposure, Cu concentrations were either lower (gills and carcasses) or higher (liver and kidney) in fish exposed to the metals mixture. On the other hand, Cd accumulation was enhanced in livers and carcasses of fish exposed to the mixture compared to those exposed to Cd alone, while Zn stimulated Cu accumulation in gills. Chronic toxicity was demonstrated by elevated malondialdehyde levels in livers and reduced concentrations of Zn and Cu in plasma. Overall, interactions of Cd, Cu and Zn are not always consistent with the isomorphous competitive binding theory.     

Cadmium and zinc accumulation and elimination by freshwater crayfish

A theoretical compartment model for the uptake of Cd and Zn by the freshwater crayfish,Procambarus acutus acutus (Girard), was constructed, and included a factorially designed experiment to study the relative importance of food and water as uptake vectors for¹⁰⁹Cd and⁶⁵Zn. Food and water were important pathways for Cd accumulation and the two uptake vectors were first order, independent, and additive. The rate of Cd elimination was not significantly different from zero during either the uptake or depuration phases. Rate constants for uptake from 5 and 10 g Cd · L^–1, calculated on a concentration basis, were 0.84 ± 0.031 and 0.83 ± 0.029 day^–1, respectively. Although there was no measurable Cd elimination, crayfish reached a steady state concentration of about 12.5g Cd · g^–1, dry weight. A small amount of Zn was accumulated via food, relative to that accumulated from water; the former had a much longer retention time than the latter, which was lost rapidly. When Zn in food was the only source, steady state was reached rapidly; Zn accumulation from food and water was not additive. Zn accumulated from water, reached no steady state. Zn uptake was proportional to water concentrations within the fed treatment groups and those not fed Zn-contaminated food. Zn elimination was first order to Zn concentration in the crayfish. Rate constants for Zn accumulation from 50 and 100 g Zn · L^–1 when fed Zn-contaminated food were 1.34 ± 0.064 and 1.46 ± 0.073 day^–1 (estimate ± 95% CI based on concentration), respectively, while rate constants for Zn elimination were 0.034 ±0.0021 and 0.05 ± 0.0032, respectively.     

Effects of environmental parameters on the elimination of cadmium by eastern oysters,Crassostrea virginica

Laboratory studies were conducted to test the effects of salinity, humic acid, and temperature on the rate of elimination of¹⁰⁹Cd from laboratory-dosed juvenile oysters,Crassostrea virginica. After 140 days, oysters maintained at 34 parts per thousand (ppt) salinity retained 67% of the¹⁰⁹Cd dose (CPM), oysters in 20 ppt salinity retained 72% and those in 6 ppt salinity retained 80%. The presence of humic acid in 14 ppt salinity water enhanced the amount of¹⁰⁹Cd eliminated in 140 days relative to oysters in control tanks without humic acid: oysters exposed to 10 parts per million (ppm) humic acid retained 65%, oysters exposed to 1 ppm humic acid retained 67%, controls retained 72%. Temperature had a significant effect on the rate of Cd elimination. Oysters held at 28°C and 20 ppt for 28 days retained 75%, oysters at 20°C and 20 ppt retained 81% and those at 12°C and 20 ppt retained 88% of¹⁰⁹Cd dose. The effects of a strong Cd-chelator, ethylenediamine tetraacetic acid-sodium salt (EDTA), were compared with those of the relatively weaker chelator, humic acid, on the rate of Cd elimination by oysters. No difference was observed between the two chelators over a 28 day depuration period. Cadmium concentrations were monitored in the water and Cd, Cu, Zn, Mg, and Fe concentrations were determined in the animals on the final day of the studies. Particle clearance assays were performed to determine if the rate of filtration by the oysters held in each of the test treatments correlated with the rates of Cd depuration. No direct correlation was observed.     

Cadmium uptake and depuration in different organs ofLymnaea stagnalis L. and the effect of cadmium on the natural zinc level

The uptake of cadmium (0.1 mg/L) into various organs of the pond snailLymnaea stagnalis L., the depuration of accumulated Cd, and the change in the natural Zn level under the influence of Cd treatment were investigated during a 2 month period. The snails were fed with lettuce (Latuca sativa). The concentrations of Cd were measured in the whole soft body, various organs (liver, viscera, foot), the shell and the lettuce; and zinc concentrations were measured in various organs and the lettuce. As its Cd concentration remained at 10 g/g, which was much lower than the initial value for the soft body (69.4±5.71 g/g), the shell, according to our results, is incapable of accumulating Cd. The uptake pattern of the soft body showed a correlation with the initial Cd levels depending on differences in the Cd concentration of the lettuce. At the higher initial value (69.4±5.71 g/g) the linear Cd uptake began later then it did at the lower initial value; afterwards the snail was saturated with Cd. In the case of the lower, 9.02±1.3 g/g initial concentration, a rapid linear Cd uptake occurred till the 7th day, then the intensity of the uptake decreased. Saturation occurred at 200 g/g Cd concentration, regardless of the initial value. At the lower initial tissue level, the foot and the viscera showed a linear uptake pattern, while the liver, which has the greatest accumulation ability, displayed a logarithmic uptake pattern. The initial and the final Cd concentrations in the foot, viscera, and liver of theL. stagnalis were as follows: 10.3±2.15–60.1±7.13, 5.15±1.04–156±27.2, 14.1±3.09–430±23.3 g/g respectively. The bioconcentration factors (CF) were in the 10² (foot) and 10³ (viscera, liver, soft body) orders of magnitude. Forty to 45% of the accumulated Cd was depurated in Cd-free tap water; during the first three days of the uptake period, a negative linear correlation was found between Cd and Zn levels in the snail organs.     

Cadmium kinetics in freshwater clams. III. Effects of zinc on uptake and distribution of cadmium inAnodonta cygnea

Freshwater clams (Anodonta cygnea) were exposed to Cd²⁺ (25 g/L) or to Cd²⁺ (25 g/L) plus Zn²⁺ (2.5 mg/L). In the presence of zinc, uptake of cadmium in whole clam was halved. In organs such as the gills, mantle, and labial palps a still larger reduction of Cd accumulation occurred. By contrast, accumulation in midgut gland and kidney was hardly affected by the presence of zinc. It is shown that in the gills zinc competes with cadmium for metal binding sites both within the particulate fraction and the high-molecular weight fraction of the cytosol. Zinc probably did not induce an enlarged synthesis of specific metal-binding, metallothionein-like, proteins. In conclusion, zinc exerts antagonistic effects on uptake of cadmium by gills, and accelerates Cd transport from the gills towards the internal organs.     

The disposition of cadmium and zinc inPandalus montagui

Cadmium uptake rates in various tissues ofPandalus montagui exposed to sea water containing 37 gCd/L for 14 days ranged from 0.002–0.06 g/g dry tissue/hr. During depuration for 57 days, the levels in most tissues decreased slightly, but continued to rise in the hepatopancreas indicating Cd redistribution. Exposure to 65 g Zn/L produced no substantial change in Zn content of the tissues. An increase occurred in eggs and hepatopancreas during the first six days of depuration. During exposure to Cd and Zn combined (40 g Cd/L + 70 g Zn/L), tissue Zn levels responded as with Zn alone. In the presence of Zn, Cd concentration was doubled in the hepatopancreas, depressed by one-third in the carcass, and did not change in the other tissues. Increased amounts of Zn (up to 410 g Zn/L) had no effect on the Cd levels of the tissues except that the Cd level in the hepatopancreas was depressed, although the level was still greater than in the case of exposure to Cd alone. The possible role of metallothionein is discussed.     

Tissue-specific cadmium accumulation, metallothionein induction, and tissue zinc and copper levels during chronic sublethal cadmium exposure in juvenile rainbow trout

Juvenile rainbow trout, on 3% of body weight daily ration, were exposed to 0 (control) or 3 μg/L Cd (as Cd(NO₃)₂· 4H₂O) in moderately hard (140 mg/L as CaCO₃), alkaline (95 mg/L as CaCO₃, pH 8.0) water for 30 days. Particular attention focused on Cd burden in tissues (gills, liver, kidney, and whole body) and induction of metallothionein (MT) in gills, liver, and kidney during chronic Cd exposure. Mortality in Cd-exposed fish was minimal (∼10%), and no growth effects occurred over the 30-day exposure. Cd accumulated in a time-dependent fashion to 9 times (gills), 3 times (liver), 20 times (kidney), 2 times (carcass), and 2 times (whole body) control levels by 30 days; absolute concentrations were in the order kidney > gill > liver > whole body > carcass. Tissue (gills, liver, and kidney) Zn and Cu burdens were not altered by chronic exposure to 3 μg/L Cd. MT concentrations in all tissues increased over the 30 days of Cd exposure, but the increases were much less than those of Cd on a molar binding site basis. Absolute MT concentrations were in the order liver > kidney > gill, but relative increases were greatest in kidney (fourfold), followed by gills (twofold) and liver (1.3-fold). MT levels were sufficient to bind all Cd in gill, liver, and kidney under control conditions, and after chronic Cd exposure remained sufficient in liver and kidney, but not in gills. Total metal levels (Cd + Zn + Cu) greatly exceeded MT binding capacity in all tissues under all conditions. Received: 20 February 2001/Accepted: 20 May 2001     

Marginal nutritional status of zinc, iron, and calcium increases cadmium retention in the duodenum and other organs of rats fed rice-based diets

Dietary minerals Zn, Fe, and Ca are antagonistic to Cd absorption. We showed earlier that rats fed a rice-based diet with a marginal content of these nutrients absorbed more Cd than rats fed adequate Zn-Fe-Ca (Environ. Sci. Technol., 36 (2002) 2684-2692). The present experiment was designed to determine the effects of marginal dietary Zn, Fe, and Ca on the uptake and turnover of Cd in the gastrointestinal tract. Two groups of weanling female rats (six per treatment) were fed a diet containing 40% cooked, dried rice containing 0.6 mg Cd/kg. The diet of one group contained adequate Zn (35 mg/kg), Fe (30 mg/kg), and Ca (5000 mg/kg), while that of the other group contained marginal Zn (6 mg/kg), Fe (9 mg/kg), and Ca (2500 mg/kg). Rats were fed for 5 weeks and then orally dosed with 1g of diet containing rice extrinsically labeled with 109Cd. From 0.25 to 64 days after dosing, 109Cd and total Cd concentrations were determined in intestinal segments. Shortly after dosing, 109Cd, as a percentage of the dose, was about 4 times higher in the duodenum of marginally fed rats than in that of control rats (10% vs 40%, respectively). Sixty-four days after dosing, 109Cd was 10 times higher in marginally fed rats than in controls; however, of the amount at day 1, <0.1% remained at day 64. After 5 weeks, the concentration of elemental Cd in the duodenum of the marginally fed rats was 8 times higher than that of control rats (24 microg/g dry wt. vs 2.9 microg/g dry wt., respectively). Cd concentrations in liver and kidney were 5 times higher in the marginally fed rats than those in controls (liver, 0.81 microg/g dry wt. vs 0.14 microg/g dry wt.; kidney, 4.7 microg/g dry wt. vs 0.92 microg/g dry wt., respectively). These data suggest that marginal intakes of Zn, Fe, and Ca cause the accumulation of Cd in the duodenum, which results in a greater rate of Cd absorption and a greater accumulation in the internal organs. Results are discussed in relation to mineral nutrient status and risk assessment of Cd in natural food sources.     

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.     

Uptake and absorption of zinc in perfused rat jejunum: The role of endogenous factors in the lumen

These studies tested whether jejunal uptake and absorption of zinc in the rat occurs in the absence of soluble endogenous factors (including putative Zn-binding ligands) in the lumen. Using isolated segments of the adult rat proximal jejunum in situ, washed free of luminal contents and perfused with a recirculating glucose-saline medium containing 20 μM Zn+⁶⁵Zn, we observed rapid mucosal uptake and efficient transmural transport of ⁶⁵Zn. Similar experiments using a non-recirculating single-pass perfusion actually revealed a somewhat greater uptake of ⁶⁵Zn making it unlikely that a factor essential for ⁶⁵Zn uptake was being secreted into the lumen by the tissue itself. The uptake and absorption of ⁶⁵Zn, ⁶⁷Cu, and ¹⁰⁹Cd in this system were all consistent with in vivo studies. We conclude that endogenous luminal factors are not an essential component of the Zn uptake system. The enhancement of Zn absorption in the intact animal by some low molecular weight Zn-binding ligands may therefore be due to their interaction with dietary Zn resulting in a more absorbable form of the metal, rather than due to replacement of a missing component of the uptake system.     

Accumulations of naphthalene and cadmium after simultaneous ingestion by the Black sea bass,Centropristis striata

Black sea bass,Centropristis striata, were daily force-fed capsules containing oyster,Crassostrea virginica, tissues previously exposed to¹⁰⁹Cd in the presence and absence of¹⁴C-naphthalene (NPH). Black sea bass were sacrificed at 24, 72, and 336 hr, and values for radioactivity associated with Cd and total NPH compounds (including NPH cellular metabolites) determined for various tissues and body fluids. Results indicated that concentrations of tissue Cd were significantly higher when both Cd and NPH were ingested simultaneously. Tissue concentrations of total NPH compounds were generally not affected by the presence of Cd.     

Alteration of dissolved cadmium and zinc uptake kinetics by metal pre-exposure in the Black Sea bream (Acanthopagrus schlegeli)

We first examined the uptake kinetics of Cd and Zn in the juvenile marine black sea bream (Acanthopagrus schlegeli) over a wide range of ambient Cd and Zn concentrations, and the relationships with metal accumulation (uptake rate and amount of nonexchangeable surface binding) were established for different fish tissues. Both Cd and Zn accumulation in the body increased linearly with exposure time after the initial metal surface binding. The dissolved Cd and Zn uptake rate constants were 2.64 and 6.50 L/kg/d, respectively, and the kinetics followed a first-order process. No evidence of biphasic transport was found, in contrast to the situation in freshwater fish. Viscera were the most important sites of metal uptake, and gills were the second most important sites. The black sea breams were then acclimated at different Cd or Zn concentrations from either waterborne or dietary source for one week, and the alteration of metal uptake kinetics or subcellular distribution and metallothionein (MT) induction were further quantified. The Cd body burden was enhanced up to 8.6- and 49-fold after waterborne and dietary Cd pre-exposure, respectively. Cadmium pre-exposure also altered the tissue-specific subcellular Cd distribution and significantly elevated tissue MT levels. In contrast, the black sea breams were able to regulate Zn accumulation, and waterborne or dietary Zn pre-exposure had only weak influences on Zn body burden and redistribution. Both Cd and Zn pre-exposures enhanced the metal uptake rate constants, whereas the nonexchangeable surface bindings were less impacted by these pre-exposures. We demonstrated a positive relationship between the Cd uptake rate and Cd or MT concentration in the fish. Pre-exposure to metals may substantially modify the kinetics of metal uptake.     

The effect of EDTA on cadmium and zinc uptake and toxicity in Lemna trisulca L.

Lemna trisulca was grown in axenic cultures with regular replacement of a filter-sterilized medium. The effect of EDTA on the uptake and toxicity of Cd and Zn was examined using a two-way factorial design of varying Cd or Zn concentrations and available EDTA. When the level of available EDTA was in excess of the Cd or Zn concentration, uptake in Lemna trisulca was reduced by 96 to 99%, and correspondingly, multiplication rates were unaffected by elevated Cd or Zn concentrations. The proportion of EDTA available for chelating Cd and Zn was the amount of EDTA in excess of the Fe concentration. The antagonistic effect of the chelator EDTA suggests that, for L. trisulca, it is the free ion activity and not the total metal concentration which determines Cd and Zn uptake and toxicity.Chelators are an essential component of a complete nutrient medium and should be included when measuring metal toxicity in aquatic plants, since Lemna trisulca grown without EDTA had low multiplication rates and appeared stunted and chlorotic. The chelator : Fe ratio, however, should be defined and controlled to avoid confounding the measurement of metal toxicity with metal-chelator interactions.     

Toxicity, accumulation, and retention of zinc by carp under normoxic and hypoxic conditions

Zinc is an essential micronutrient that becomes toxic at elevated concentrations. Under hypoxic events, i.e., temporal depletion of oxygen, the toxicity of Zn increases for fish, apart from the direct effects of the reduced oxygen levels. This enhanced toxicity currently is explained by the increased ventilation rates under hypoxia, causing a higher water flow over the gills. However, the few experimental studies available on the uptake of heavy metals under hypoxia draw contradictory conclusions. The present study verifies the enhanced zinc toxicity under hypoxia and tests whether accumulation of zinc is increased in common carp, Cyprinus carpio (L.). Second, the effect of acclimatization to three oxygen levels (100, 50, and 25% saturation) on the zinc uptake and elimination was studied in a standard radiotracer uptake-and-elimination study for 63 d at 100 nmol/L Zn and 25 degrees C. The sensitivity of carp for Zn was threefold higher under hypoxia than at normoxic conditions. The lethal concentration for 50% of the population after 96 h (96-h LC50) for normoxia and hypoxia (25%) were 149 (91-317) and 55 (30-100) micromol/L Zn, respectively. However, the kinetic data indicate that zinc uptake and elimination are not altered under hypoxia for common carp. Moreover, observed uptake rates are considerably lower than predicted from a ventilation-and-diffusion-regulated uptake mechanism. Setting these results in the framework of similar experiments of other investigators, we conclude that, in general, metal uptake in fish is not related to its ventilation rate within a normal physiological range.     

Toxicity of copper,lead, and zinc mixtures to Ceriodaphnia dubia and Daphnia carinata

Acute and chronic bioassays were conducted to determine the effects of copper, lead, and zinc mixtures on Ceriodaphnia dubia and Daphnia carinata. Copper, lead, and zinc combined at up to 5.2, 4.5, and 51.8 μg/L, respectively, did not cause significant mortality during acute exposures, although mixtures of 10.6, 9, and 101.1 μg/L and higher resulted in 65–100% mortality. Binary combinations of Cu+Zn (1.3+13.0 μg/L) and Cu+Pb (1.3+1.1 μg/L) and ternary combinations of Cu+Pb+Zn (1.3+1.1+13.0 μg/L) had a significant effect on reproduction of C. dubia. Toxic units and associated confidence intervals were calculated to characterize the nature of metal interactions. In most cases, and based on confidence intervals encompassing a value of 1, most of the metal interactions would be classified as additive. However, a more than additive effect was indicated by the acute tests for both species exposed to Cu+Pb, for D. carinata exposed to Cu+Zn, and for C. dubia exposed to all three metals.     

Low iron stores are related to higher blood concentrations of manganese, cobalt and cadmium in non-smoking, Norwegian women in the HUNT 2 study

Low iron (Fe) stores may influence absorption or transport of divalent metals in blood. To obtain more knowledge about such associations, the divalent metal ions cadmium (Cd), manganese (Mn), cobalt (Co), copper (Cu), zinc (Zn) and lead (Pb) and parameters of Fe metabolism (serum ferritin, haemoglobin (Hb) and transferrin) were investigated in 448 healthy, menstruating non-smoking women, age 20-55 years (mean 38 years), participating in the Norwegian HUNT 2 study.The study population was stratified for serum ferritin: 257 were iron-depleted (serum ferritin <12 μg/L) and 84 had iron deficiency anaemia (serum ferritin <12 μg/L and Hb<120 g/L). The low ferritin group had increased blood concentrations of Mn, Co and Cd but normal concentrations of Cu, Zn and Pb. In multiple regression models, ferritin emerged as the main determinant of Mn, Co and Cd (p<0.001), while no significant associations with Cu, Zn and Pb were found. Adjusted r² for the models were 0.28, 0.48 and 0.34, respectively. Strong positive associations between blood concentrations of Mn, Co and Cd were observed, also when controlled for their common association with ferritin. Apart from these associations, the models showed no significant interactions between the six divalent metals studied. Very mild anaemia (110≤Hb<120 g/L) did not seem to have any effect independent of low ferritin. Approximately 26% of the women with iron deficiency anaemia had high concentrations of all of Mn, Co and Cd as opposed to 2.3% of iron-replete subjects.The results confirm that low serum ferritin may have an impact on body kinetics of certain divalent metal ions, but not all. Only a fraction of women with low iron status exhibited an increased blood concentration of divalent metals, providing indication of complexities in the body's handling of these metals.     

Evidence of zinc deficiency in competitive swimmers

ObjectiveThe aim of this study was to assess the nutritional zinc (Zn) status of elite swimmers during different training periods.MethodsA longitudinal paired study was performed at the University of Sao Paulo in eight male swimmers 18 to 25 y old who had been swimming competitively at the state and national levels for at least 5 y. The swimmers were evaluated over a total period of 14 wk: before the basic and specific preparatory period (BSPP-baseline), at the end of the basic and specific preparatory period (post-BSPP), and at the end of the polishing period (PP). Levels of Zn were determined in the plasma, erythrocyte, urine, and saliva by atomic absorption spectrophotometry. Anthropometric measurements and a 3-d food record were also evaluated.ResultsThe median plasma Zn concentration was below the reference value in all training periods (BSPP-baseline 59 μg/dL, post-BSPP 55.9 μg/dL, after PP 58.8 μg/dL, P > 0.05), as were threshold values for erythrocytes (BSPP-baseline 36.5 μg of Zn/g of hemoglobin, post-BSPP 42 μg of Zn/g of hemoglobin, after PP 40.7 μg of Zn/g of hemoglobin, P > 0.05), urinary Zn (BSPP-baseline 280 μg/24 h, post-BSPP 337 μg/24 h, after PP 284 μg/24 h, P > 0.05), and salivary Zn (BSPP-baseline 66.1 μg/L, post-BSPP 54.1 μg/L, after PP 79.7 μg/L, P > 0.05). Salivary Zn did not correlate with plasma and erythrocyte Zn levels.ConclusionThe results suggest that the elite swimmers studied presented a possible Zn deficiency and that salivary Zn was not adequate to evaluate the Zn nutritional status.     

Biological Difference Cadminum and Zinc Turnover

In rat plasma, ¹⁰⁹Cd was mainly associated with α-globulin fraction and ⁶⁵Zn was bound to and β-globulins. Subcutaneously injected cadmium chloride Cd 109 and zinc chloride Zn 65 resulted in rapid clearance of ¹⁰⁹Cd from blood plasma, as compared to ⁶⁵Zn. Blood cells accumulated ⁶⁵Zn more rapidity than ¹⁰⁹Cd. Greatest uptakes of ¹⁰⁹Cd per unit weight of tissue were by liver, kidneys, and pancreas, but that of ⁶⁵Zn was by the pancreas. From all tissues, ⁶⁵Zn was depleted eventually. In the first six hours after isotope dose, testis tissue concentrated more ¹⁰⁹Cd than ⁶⁵Zn. In testes, ⁶⁵Zn-influx continued for 168 hours, without further ¹⁰⁹Cd increase. Both isotopes were excreted predominantly via intestinal tract. Fecal and urinary excretion of ¹⁰⁹Cd and ⁶⁵Zn was accelerated by 2,3-dimercapto-1-propanol Results Indicate ¹⁰⁹Cd follows metabolic pathways different from those of ⁶⁵Zn.     

Cadmium uptake by the crayfish, Orconectes propinquus propinquus (Girard)

Orconectes propinquus was exposed to 10, 100, and 1000 ppb Cd(Cl₂) containing 0.09 μCi/liter ¹⁰⁹ Cd(Cl₂) for 1.5, 4.5, 10.5, 22.5, 46.5, 94.5, and 190.5 hours. At 10 ppb, total Cd uptakes between 1.5 and 94.5 hours were not significantly different. By 190.5 hours, the organisms had accumulated a mean concentration of 18.4 ppm Cd, which was significantly higher than the concentrations accumulated at earlier times. At 100 ppb, Cd uptake at 1.5 hours was significantly less (P < 0.05) than that at 22.5–190.5 hours and uptake at 4.5 hours was significantly less than that at 94.5 and 190.5 hours. Also, uptake at 10.5 hours was significantly less than that at 190.5 hours. Uptakes were not significantly different between 22.5 and 94.5 hours; but were significantly higher than at 1.5 hours and lower than at 190.5 hours. At 1000 ppb, uptake increased with time and was significantly greater (P < 0.05) at every time interval monitored. By 190.5 hours, the organisms had accumulated a mean Cd concentration of 534.4 ppm. At all time intervals at 1000 ppb, Cd uptake was significantly higher (P < 0.01) than that at 100 and 10 ppb. Uptakes at 100 and 10 ppb were not significantly different.