Influence of selenium dose on mercury distribution and retention in suckling rats.

It is well known that metal-metal interactions in the body are age-dependent. We studied the influence of increasing selenium (Se) doses on mercury (Hg) distribution and retention in the postnatal period in Hg-exposed suckling rats. Seven-day-old Wistar pups were pretreated with three different oral doses of Se as sodium selenite (6.45, 12.9 and 19.4 micromol Se kg(-1) b.w.) over 3 days. This was followed by simultaneous Se (as sodium selenite) and Hg (as mercury chloride) oral administration over 4 days. The molar ratio between Se and Hg given to pups was 1:1, 2:1 and 3:1, respectively. Mercury and Se were measured in brain, kidneys, liver, plasma, erythrocytes and urine of pups on the day after the last administration by atomic absorption spectrometry. Results showed that in all samples Se concentrations rose almost proportionally to the dose of Se given to pups. Mercury concentration in organs, plasma and urine decreased with higher oral doses of Se. However, Hg concentration in erythrocytes increased with increasing Se dose. There was evidently a redistribution of Hg from plasma to erythrocytes at higher ratio of Se:Hg. Approximately equimolar doses of Se and Hg are necessary to produce maximum uptake of Hg by plasma and liver and minimum retention of Hg in the kidney and erythrocytes.

Comparison of calcium, magnesium, sodium, potassium, zinc, and creatinine concentration in 24-h and spot urine samples in women.

BACKGROUND: The 24-h urine sample is considered as the most reliable material for testing many but not necessarily all constituents in urine. However, its collection is tedious for both patients and research participants. The aim of this study was to compare concentrations of essential elements calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), and zinc (Zn) in 24-h and spot urine samples. METHODS: Urine samples were collected from 143 generally healthy women, aged 30-79 years. Fasting spot urine was collected immediately after the end of the 24-h collection, therefore being of the same content as the first morning urine which ended the 24-h collection. Elements were analyzed by flame atomic absorption/emission spectrometry and expressed as mg/g and/or mmol/mol of creatinine (Cr). Spearman rank order correlations between 24-h and spot urine were carried out for each element. Ratios of elements in 24-h to spot urine samples were calculated to estimate the element-proportion of spot in the 24-h sample. RESULTS: All coefficients of correlation between 24-h and spot urine of measured elements and Cr were significant (p<0.05): Zn (0.637), Mg (0.623), Ca (0.603), Na (0.452), K (0.396), and Cr (0.217). Ratios of 24-h to spot urine samples for each element (except K) were similar and close to 2, indicating uniform proportion of elements from spot urine sample in the 24-h sample. In addition, a high correlation between various pairs of elements was obtained in both 24-h and spot urine; the highest being between Na/Ca (0.435) and (0.578), respectively. This is in accordance with theoretical presumptions and previous findings regarding those relationships. CONCLUSIONS: Although replacing burdensome 24-h urine collection with spot urine sampling might not provide the solution in all cases, our results show that for the elements analyzed, spot urine could be a reliable alternative.

Comparison of organic and inorganic mercury distribution in suckling rat.

Thiomersal is used as a preservative in vaccines given to small children. The metabolic product of thiomersal is ethylmercury and its distribution and kinetics are still not known, especially at this early age. The purpose of this study was to compare the body distribution of two forms of mercury: organic (thiomersal) and inorganic (mercury(2+) chloride) in very young, suckling rats. Mercury was applied subcutaneously three times during the suckling period on days 7, 9 and 11 of pups age, imitating the vaccination of infants. A single dose of mercury was equimolar in both exposed groups, i.e. 0.81 micromol Hg kg(-1). At 14 days of age the animals were killed and the total mercury analysed in blood and organs (kidney, liver and brain). The analytical method applied was total decomposition, amalgamation, atomic absorption spectrometry. The results showed that the level of mercury was higher in the liver and kidney of the inorganic mercury group than in the thiomersal exposed group. However, the brain and blood concentrations of mercury were higher in the thiomersal exposed group. These results need to be clarified by additional data on the kinetic pathways of ethylmercury compared with inorganic mercury.

Chelators as antidotes of metal toxicity: therapeutic and experimental aspects.

The effects of chelating drugs used clinically as antidotes to metal toxicity are reviewed. Human exposure to a number of metals such as lead, cadmium, mercury, manganese, aluminum, iron, copper, thallium, arsenic, chromium, nickel and platinum may lead to toxic effects, which are different for each metal. Similarly the pharmacokinetic data, clinical use and adverse effects of most of the chelating drugs used in human metal poisoning are also different for each chelating drug. The chelating drugs with worldwide application are dimercaprol (BAL), succimer (meso-DMSA), unithiol (DMPS), D-penicillamine (DPA), N-acetyl-D-penicillamine (NAPA), calcium disodium ethylenediaminetetraacetate (CaNa(2)EDTA), calcium trisodium or zinc trisodium diethylenetriaminepentaacetate (CaNa(3)DTPA, ZnNa(3)DTPA), deferoxamine (DFO), deferiprone (L1), triethylenetetraamine (trientine), N-acetylcysteine (NAC), and Prussian blue (PB). Several new synthetic homologues and experimental chelating agents have been designed and tested in vivo for their metal binding effects. These include three groups of synthetic chelators, namely the polyaminopolycarboxylic acids (EDTA and DTPA), the derivatives of BAL (DMPS, DMSA and mono- and dialkylesters of DMSA) and the carbodithioates. Many factors have been shown to affect the efficacy of the chelation treatment in metal poisoning. Within this context it has been shown in experiments using young and adult animals that metal toxicity and chelation effects could be influenced by age. These findings may have a bearing in the design of new therapeutic chelation protocols for metal toxicity.

Sodium and calcium intakes and bone mass in rats revisited.

OBJECTIVE: High sodium intake accompanied by insufficient dietary calcium may have detrimental effects on bone mass. Our study evaluated the effects of increased sodium and decreased calcium intakes on bone mineral density (BMD) and bone mineral content (BMC) in rats. METHODS: Four-month-old female Wistar rats were given deionized water or 1.8% solution of sodium chloride in deionized water and fed normal (1.2%) or marginal (0.33%) calcium in the diet for 2 mo. At the end of the experiment, BMD and BMC of the whole body and urinary sodium and calcium excretion were evaluated. All rats were killed and right femurs were removed to assess dry and ash weights. Two-way analysis of variance was used to evaluate effect of salt intake and effect of dietary calcium on these parameters. RESULTS: Salt-loaded animals had greater water consumption during the entire 2-mo period and significantly lower body weight from week 5 of the experiment. High salt intake increased urine volume and urinary excretion of sodium and calcium. Urinary calcium was about five times higher in salt-loaded animals than in rats on deionized water irrespective of dietary calcium content. Calcium in diet itself had no significant effect on these parameters. High salt intake slightly, but not significantly, decreased BMD, BMC, and femur weights. Lower calcium in diet significantly decreased BMD, and its effect on femur ash weight almost reached a level of significance. CONCLUSION: We confirmed the benefit of adequate calcium intake to BMD. Under our experimental condition, high salt intake in rats for 2 mo had no statistically significant effect on femur weights, BMD, or BMC even with marginal calcium in the diet.

Regulation of manganese accumulation in perinatally exposed rat pups.

The risk of manganese (Mn)-related ill effects in the neonate has been the topic of several investigations because in formula-fed infants Mn intake is much higher than in breast-fed infants. In the young, when Mn homeostasis is not yet developed, increased Mn intake might pose a neurotoxic risk. Our work aimed at collecting new data on Mn accumulation during the perinatal period by using an experimental rat model in pups whose mothers were exposed orally to Mn in drink (as manganese chloride; dose of 2000 ppm Mn) throughout pregnancy and 11 days of lactation. Pups were cross-fostered at birth and placental and mammary transfer of Mn at birth and at the age of 11 days was evaluated. The total pup body burden of Mn was analysed by atomic absorption spectrometry. Concentrations of iron (Fe), zinc (Zn) and calcium (Ca) also were analysed at the end of the experiment. The concentration of Mn in perinatally exposed pups was 6-8 times higher than in controls, irrespective of the period and duration of exposure. After cessation of exposure, the Mn concentration decreased almost to control levels. Concentrations of other essential elements (Fe, Zn, Ca) were not affected by Mn exposure. Our results indicate the existence of an accurate regulation of Mn accumulation in pups exposed to Mn during the perinatal period.

Simultaneous administration of sodium selenite and mercuric chloride decreases efficacy of DMSA and DMPS in mercury elimination in rats.

Two chelating agents meso-2,3-dimercaptosuccinic acid (DMSA) and sodium 2,3-dimercapto-propane-1-sulphonate (DMPS) were tested for their efficiency in mercury removal from the body of rats in the presence and in the absence of selenium. Female Wistar rats were given a single intraperitoneal injection of mercuric chloride or an equimolar mixture of mercuric chloride and sodium selenite (1.5 micromol/kg body weight). The chelating agents were given orally, in excess (500 micromol DMSA/kg body weight; 300 micromol DMPS/kg body weight), 30 min after the administration of mercury and selenium. The animals were euthanized 24 h after the treatment and mercury in the kidney, liver, and 24 h urine was determined using cold vapour atomic absorption spectrometry (CV-AAS). The simultaneous administration of mercuric chloride and sodium selenite led to a redistribution of mercury in the organs, so that accumulation of mercury in the kidneys was decreased and in the liver increased. Selenite also caused decrease in the level of urinary mercury excretion. Both chelating agents were effective in mercury removal from the body, by increasing its urinary excretion. However, when animals were simultaneously treated with mercury and selenite, the rise of mercury excreted in the urine due to the treatment with chelating agents was lower when compared to animals receiving mercury without selenite. It is concluded that sodium selenite decreases the efficiency of DMSA and DMPS in mercury removal from the body of rats.

Succimer treatment and calcium supplementation reduce tissue lead in suckling rats.

The effect of combined treatment with meso-2,3-dimercaptosuccinic acid (DMSA) and calcium supplementation in reducing lead absorption and enhancing lead elimination was evaluated in suckling rats under two experimental conditions: during ongoing oral lead exposure (lead acetate, 2 mg Pb kg(-1) day(-1), total dose 16 mg Pb kg(-1)) or after lead exposure (72 h after a 2-day lead exposure, total dose 12 mg Pb kg(-1) s.c.). The artificial feeding method was used for calcium supplementation, with 6% Ca (as CaHPO(4)) suspension in cow's milk to increase the daily calcium intake about three times above control values. Artificial feeding lasted for 7 h a day over eight consecutive days. During this period DMSA was administered on 6 days twice a day (0.5 mmol kg(-1) day(-1) p.o.). At the end of the experiments, Pb, Ca and Zn in the carcass and Pb, Fe and Cu in the liver, kidneys and brain were analysed by atomic absorption spectrometry. Calcium supplementation during lead exposure reduced tissue lead but had no effect when applied after lead exposure, and DMSA administered either during or after lead exposure lowered the tissue lead. Combined treatment during ongoing lead exposure caused a greater reduction in tissue lead than either DMSA or calcium treatment alone. When administered after lead exposure, it had no advantage over DMSA treatment alone but did not impair its efficacy. Combined treatment had no influence on growth and did not seriously disturb essential element status. It is concluded that calcium supplementation could be applied during DMSA therapy, when indicated.

Combined early treatment with chelating agents DMSA and CaDTPA in acute oral cadmium exposure.

The influence of chelating agents: meso-2,3-dimercaptosuccinic acid (DMSA); calcium trisodium diethylenetriaminepentaacetate (CaDTPA) and their combination on mobilisation of cadmium (Cd) was compared in female albino rats. After oral Cd administration chelators were applied either orally (DMSA) or intraperitoneally (CaDTPA) at various short time intervals after Cd. Three experiments were carried out with four treatment groups in each: 1) Cd (control); 2) Cd+DMSA; 3) Cd+CaDTPA; 4) Cd+DMSA+CaDTPA. Time intervals for chelator treatment after Cd administration were: immediate application in the first, half an hour in the second and one hour in the third experiment. At the end of each experiment cadmium was analysed in kidney and liver. Additionally in experiment 3 essential elements (Fe, Cu, Zn) were also determined in the same organs. In experiment 2 the effect of the treatment on urinary elimination of cadmium, copper and zinc were analysed. Results showed that the efficiency of Cd removal from the body (kidneys and liver) is lower when the time between Cd and chelating agents administration is longer. The two chelators differ in efficiency in mobilizing Cd, with DMSA being more efficient than CaDTPA. The combined therapy with the two chelators gave generally better results. It seems that DMSA which is given orally after oral Cd administration removes this element very efficiently from the gastrointestinal tract. CaDTPA, however, which is given parenterally removes absorbed Cd less efficiently, Organs are not significantly depleted in iron and copper after chelation treatment. Only zinc concentration was, however, significantly lower in the liver and higher in kidneys only after CaDTPA and combined DMSA+CaDTPA chelation.

Low iron diet and parenteral cadmium exposure in pregnant rats: the effects on trace elements and fetal viability.

The effects of latent iron deficiency combined with parenteral subchronic or acute cadmium exposure during pregnancy on maternal and fetal tissue distribution of cadmium, iron and zinc, and on fetal viability were evaluated. Timed-pregnant Sprague-Dawley rats were fed on semisynthetic test diets with either high iron (240 mg kg) or low iron (10 mg kg), and concomitantly exposed to 0, 3 or 5 mg cadmium (as anhydrous CdCl2) per kilogram body weight. Animals were exposed to cadmium from gestation day 1 through 19 by subcutaneously implanted mini pumps (Subchronic exposure) or on gestation day 15 by a single subcutaneous injection (Acute exposure). All rats were killed on gestation day 19. Blood samples, selected organs and fetuses were removed and prepared for element analyses by atomic absorption spectrometry. Low iron diet caused decreases in maternal body weight, maternal and fetal liver weights, placental weights and tissue iron concentrations. By cadmium exposure, both subchronic and acute, tissue cadmium concentrations were increased and the increase was dose-related, maternal liver and kidney zinc concentrations were increased, and fetal zinc concentration was decreased. Cadmium concentration in maternal liver was additionally increased by low iron diet. Acute cadmium exposure caused lower maternal body and organ weights, high fetal mortality, and decreased fetal weights of survivors. In conclusion, parenteral cadmium exposure during pregnancy causes perturbations in essential elements in maternal and fetal compartments. Acute cadmium exposure in the last trimester of gestation poses a risk for fetal viability especially when combined with low iron in maternal diet.

The effect of dietary supplementation with calcium salts on skeletal calcium in suckling rats.

This study aimed at identifying a calcium compound which could serve as an effective and safe dietary supplement in suckling rats over the period of intense growth and development. The main objective was to assess the effect of additional calcium intake on skeletal calcium in suckling pups. Suckling Wistar rats were fed using a pipettor with one of the following calcium salts from day 6 to 14 after the birth: gluconate, hydrogenphosphate, carbonate (each suspended in cow's milk), or chloride (in demineralized water). Control rats received only cow's milk. Calcium in the carcass (body without organs and skin) was analysed by atomic absorption spectrometry. The only effective dietary supplement that produced no risk for the suckling pups' growth was calcium hydrogenphosphate in cow's milk in the total amount of 340 mg. That dose increased the daily calcium intake 3 to 4 times compared to non-supplemented controls, increasing carcass calcium content by about 16 per cent. Other calcium compounds were either inefficient (carbonate) or had adverse effects on pups' growth (chloride and gluconate).

Ascorbic acid supplementation does not improve efficacy of meso-dimercaptosuccinic acid treatment in lead-exposed suckling rats.

It was suggested that ascorbic acid as a natural chelating agent can influence lead toxicokinetics and improve chelating properties of dimercaptosuccinic acid (DMSA) in adult rats. In this paper potential benefits of ascorbic acid supplementation, alone or combined with DMSA, in decreasing lead retention in suckling rats were evaluated. Such data in young mammals are not available. L-Ascorbic acid (daily dose 650 mg/kg b.wt.) and/or DMSA (daily dose 91 mg/kg b.wt.) were administered orally to suckling Wistar rats either during ongoing 8-day oral lead exposure (as acetate; daily dose 2 mg lead/kg b.wt.) or after 3-day lead exposure (total dose 12 mg lead/kg b.wt.). Lead concentrations were analysed in the carcass (skeleton), liver, kidneys and brain by atomic absorption spectrometry. By ascorbic acid supplementation lead retention was not reduced under either lead exposure condition. Lead concentration was even increased in the carcass. Treatment with DMSA under both exposure conditions significantly reduced lead in all analysed tissues. Combined treatment with ascorbic acid and DMSA during ongoing lead exposure was substantially less effective than DMSA treatment alone, and did not affect DMSA efficacy when administered after lead exposure. It was concluded that ascorbic acid administered either during or after lead exposure in suckling rats has no beneficial effect on either lead retention or DMSA chelation effectiveness.

Assessment of steroid disruption using cultures of whole ovary and/or placenta in rat and in human placental tissue.

OBJECTIVES: The paper presents results of collaborative research on cadmium as an endocrine disruptor. To detect steroidogenic alterations in cycling and pregnant rats following cadmium exposures in vivo (at 3 or 5 mg/kg as a single s.c. dose) and in vitro (from 0 through 2000 microM Cd(2+)) whole-ovary culture was used. To evaluate steroid productions in rats fed low iron (10 ppm) and concomitantly exposed to cadmium (5 mg/kg total dose by s.c.-implanted osmotic pumps) during 19 days of pregnancy whole-placenta culture was also used. In human placental tissue cadmium and progesterone concentrations were assessed in relation to cigarette smoking. METHODS: Cultures of minced ovaries were evaluated for 1-h basal steroid production and following 1-h production stimulated with either human chorionic gonadotropin (hCG) or hCG and pregnenolone. Placental cultures were evaluated for average 1-h progesterone production following 3 h of unstimulated production. Steroid hormones were evaluated by specific radioimmunoassay. Placental cadmium concentrations were analyzed by atomic absorption spectrometry. RESULTS: In-vivo cadmium exposure interfered with normal steroidogenesis in cycling rats and in early pregnancy, with ovarian estradiol production the most affected. Under in-vitro cadmium exposure the most affected was ovarian production of progesterone and testosterone in cycling (proestrous) rats with medial inhibitory concentrations under 500 micro M Cd(2+). Cadmium interfered with the steroidogenic pathway at more than one site. Linear and additive effects of low-iron feeding and concomitant cadmium exposure during pregnancy on placental progesterone production were found. In humans, we found that the placentas of smoking mothers contained twice as much cadmium and approximately half the amount of progesterone than did the placentas of non-smoking mothers. CONCLUSIONS: Results of the research on cadmium-induced steroidogenic effects using cultures of whole rat ovary and/or placenta as well as human placental tissues point to cadmium as an endocrine disruptor that may compromise pregnancy outcome and fetal viability.

Effect of dietary calcium on cadmium absorption and retention in suckling rats.

The effect of calcium supplementation on absorption and retention of cadmium in the suckling period was evaluated in Wistar rat pups of both sexes. Animals were maintained in the litters with the mother rats and supplemented with 1%, 3% or 6% calcium (as CaHPO4 x 2H2O) in cow's milk by artificial feeding from day of birth 6 through 14. All rats were exposed to cadmium (as CdCl2 x H2O) either orally or parenterally. Oral cadmium dose of 0.5 mg/kg body weight a day was administered through nine-day period of calcium supplementation and parenteral cadmium dose was injected subcutaneously in a single dose of 0.5 mg Cd/kg body weight prior to calcium supplementation. On experimental day 10 (at the age of pups of 15 days) all animals were killed and the liver, kidneys, brain and carcass (body without organs and skin) were removed for element analyses. Cadmium and essential elements calcium, zinc and iron were analysed in the tissues by atomic absorption spectrometry. Results showed that after oral exposure cadmium concentrations in all calcium-supplemented groups were significantly decreased in the organs and carcass and that the effect was dose-related. No such effect of calcium was found after parenteral cadmium exposure. Calcium supplementation per se significantly increased calcium concentration in the carcass and had no effect on iron in organs and zinc in carcass. It was concluded that calcium supplementation during the suckling period could be an efficient way of reducing oral cadmium absorption and retention without affecting tissue essential trace element concentrations.