Placental cadmium and progesterone concentrations in cigarette smokers.

Cadmium and progesterone concentrations were evaluated in term placentas collected from 56 healthy parturients in the city of Zagreb. Concentrations of lead, iron, zinc, and copper in placentas were analyzed. Data collected by questionnaire identified 29 nonsmoking and 27 smoking women. From each placenta, three samples from different locations were taken. Metals were measured by atomic absorption spectrometry. Progesterone was determined by specific radioimmunoassay in homogenized and lyophilized tissue samples after steroid extraction with ethanol. No effect of sample location was found. In placentas of smoking women an increase in cadmium, reduced progesterone and a decrease in iron concentrations were found. Placental copper and zinc concentrations were not altered. In conclusion, the results present new evidence that maternal smoking reduces placental progesterone content and support the established association of smoking with placental cadmium.

Succimer treatment during ongoing lead exposure reduces tissue lead in suckling rats.

There is a concern that oral treatment with succimer (meso-2, 3-dimercaptosuccinic acid, DMSA) can promote gastrointestinal lead absorption if not performed in a lead-safe environment. The scope of our investigation was to evaluate the efficacy of oral DMSA treatment during oral lead exposure on tissue lead in suckling rats. Six-day-old Wistar rats of both genders were divided into two groups-untreated (Pb) and treated (Pb + DMSA)-with 10 animals per group. Lead (as acetate) was given orally at a dose of 2 mg kg(-1) body weight day(-1) for eight consecutive days (total dose 16 mg kg(-1), i.e. 0.08 mmol kg(-1)). During this period the treated group received a daily dose of 0.5 mmol DMSA kg(-1) body weight p.o. six times on days 1-3 and 6-8 of the experiment (total dose 3 mmol kg(-1)). Tissue lead was determined by means of atomic absorption spectrometry. The DMSA efficiently reduced the lead concentration in the analysed tissues (carcass, liver, kidneys and brain) by approximately 50% compared with untreated controls. The pups' growth and organ weights were not affected. In conclusion, our results indicate that DMSA is an efficient oral lead chelator in sucklings even if challenged with ongoing lead exposure.

Calcium supplementation efficiently reduces lead absorption in suckling rats.

The effect of calcium supplementation on tissue lead was evaluated in suckling Wistar rats. Such data are not yet available in the literature. The following artificial feeding regimen was used for calcium supplementation: cow's milk by addition of 1%, 3% or 6% Ca as CaHPO(4)x2H(2)O suspension to increase the daily calcium intake about 1.4, 2 or 3 times above control values. Artificial feeding was applied during 7 hr each day for nine consecutive days (from day 6 through 15 after birth). The effect of such treatment on lead absorption and elimination was evaluated in two separate experiments: calcium supplementation during oral lead exposure (as acetate; daily dose 2 mg Pb/kg body wt.; total Pb dose 18 mg/kg body wt.) or after a single intraperitoneal lead administration (5 mg/kg body wt.). At the end of experiments, lead in tissues (liver, kidneys, brain and carcass), and essential elements (Ca, Fe, Zn, Cu) were analysed by atomic absorption spectrometry. Calcium supplementation caused a statistically significant decrease of lead in all tissues of sucklings orally exposed to lead. This decrease was dose-related being about 1.3, 1.5 and 2 times lower in groups supplemented with 1%, 3%, or 6% calcium compared to controls, respectively. Increased calcium intake had no effect on incorporated lead after parenteral lead exposure. Calcium supplementation increased carcass calcium and had no effect on trace elements in tissues, pups' general appearance and body weight gain. It is concluded that higher calcium intake might be a way of efficient reduction of lead absorption during the suckling period.

Mobilisation of cadmium by meso- and racemic-2,3-dimercaptosuccinic acid (DMSA) in rats.

A higher efficiency of cadmium binding with racemic than with meso-2,3-dimercaptosuccinic acid (rac-DMSA; meso-DMSA) was found in an in vitro speciation model by Fang et al. (1996). This finding has not yet been tested in vivo. This paper presents results on mobilisation of cadmium by meso- and rac-DMSA in rats. Cadmium chloride was administered as the radioactive isotope 109Cd intraperitoneally to all animals. One group was an untreated control and two groups were treated with meso- and rac-DMSA, respectively. Treatment with chelators was applied twice, immediately after 109Cd and 24 hr afterwards intraperitoneally at the dose of 1 mmol/kg, each. Six days later radioactivity was measured in the liver and kidneys. Whole-body counting was carried out on days 1, 2, 3 and 6 of the experiment. At the end of the experiment, both treatments caused a decrease in 109Cd whole-body retention with rac-DMSA being more efficient (decrease from 83% in control to 74% and 64% in groups treated with meso- and rac-DMSA, respectively). The same reduction of 109Cd was obtained by both chelators in the liver (from 57% to about 47%). In the kidney only rac-DMSA produced significant reduction of 109Cd (from 5.3% to 3.5%). In conclusion, these results show modest reduction of cadmium in the body by two isoforms of DMSA with rac-DMSA being slightly more efficient than meso-DMSA.

Chelation of aluminium by combining DFO and L1 in rats.

The hypothesis that two known chelators 1, 2-dimethyl-3-hydroxypyrid-4-one (L1) and desferrioxamine (DFO) might be more efficient as combined treatment than as monotherapies in removing aluminium from the body was tested in a new acute rat model. Five-week old female rats received chelators: L1 (p.o.), DFO (i.p.) or L1+DFO as 100 or 200 mg/kg dose half an hour after a single i.p. administration of 6 mg Al/kg body weight in the form of chloride. Serum aluminium concentration and urinary aluminium and iron excretions were determined by electrothermal or flame atomic absorption spectrometry. Both chelators were effective only at the higher dose level. While DFO was more effective than L1 in enhancing urinary aluminium excretion, L1 was more effective than DFO in enhancing urinary iron excretion. In the combined treatment group L1 did not increase the DFO effect on aluminium and DFO did not increase the effect of L1 on iron elimination. However, in this group a simultaneous increase in both aluminium and iron elimination was observed. Our results support the usefulness of this animal model for preliminary in vivo testing of aluminium chelators. Urinary values were more useful because of the high variability of serum results. Result of combined chelators treatment should be confirmed in a different experimental model before extrapolation to other systems. This testing procedure of course does not provide all the relevant answers for evaluating the efficiency of chelating agents in aluminium toxicity.

Combined chelation therapy in reducing tissue lead concentrations in suckling rats.

The very young are more prone to lead poisoning than adults, and the treatment with chelating agents, either as monotherapy or combined treatment, is still a matter of dispute. The purpose of this work was to evaluate the efficiency of three chelating agents administered either as monotherapies or as combined treatments in sucklings. Lead acetate (5 mg Pb kg(-1) i.p.) was administered to the 7-day-old rat pups in eight litters on experimental day 1 and chelating agents on experimental days 2 and 3. Pups were divided into six groups: (1) untreated control; (2) EDTA (calcium disodium ethylendiaminetetraacetate, 0.3 mmol kg(-1) i.p. at 4 p.m.); (3) meso-DMSA (meso-2,3-dimeracaptosuccinic acid, 0.5 mmol kg(-1) p.o. at 10 a.m.); (4) rac-DMSA (racemic-2,3-dimeracaptosuccinic acid, 0.5 mmol kg(-1) p.o. at 10 a.m.); (5) EDTA+meso-DMSA; and (6) EDTA+rac-DMSA. Rats were killed on experimental day 5. Tissue element concentrations were analyzed by atomic absorption spectrometry. Treatment with EDTA did not affect tissue Pb, but it reduced Zn in the carcass and liver. Meso-DMSA reduced Pb in the kidneys and brain, and it did not affect organ essential elements. Rac-DMSA most efficiently reduced Pb concentrations in the carcass, kidneys and brain, but it also reduced Zn and Cu in the liver and Zn in the kidneys. Combined treatments with EDTA never improved the efficiency of either DMSA isoform in decreasing tissue Pb but they did reduce tissue Zn concentrations. All treatments caused the same decrease in the carcass Ca concentrations. The results do not support combined treatment in this age group, which is especially sensitive to trace element deficiencies, and suggest that meso-DMSA might be the treatment of choice in acute lead poisoning in infants.

Combined oral treatment with racemic and meso-2,3-dimercaptosuccinic acid for removal of mercury in rats.

Racemic dimercaptosuccinic acid (DMSA) was found more efficient than the meso-isoform in enhancing the removal of mercury in rats. However, racemic-DMSA has recently been found more toxic. The efficiency of combined oral treatment with the two isoforms of DMSA for removal of mercury has now been evaluated. Female albino rats were treated orally for four days with meso- (M) and/or racemic- (R) DMSA (1 mmol/kg each), five days after a single intraperitoneal administration of 203Hg with 0.5 mg HgCl2/kg. The animals were divided into six groups according to the number of treatments with each isomer: control (untreated), 4M, 1R + 3M, 2R + 2M, 3R + 1M, and 4R. Whole body, kidney, liver and brain mercury contents were measured nine days after 203Hg administration. In all treated groups retention in the whole body and kidneys was greatly reduced. The groups treated with racemic-DMSA, regardless of the number of doses, showed a greater removal of mercury than the group treated with meso-DMSA alone (4M). All treatments were less efficient in reducing liver retention, and the brain retention was not affected. It was concluded that even a single application of the more toxic racemic-DMSA during a four-day oral treatment regimen is sufficient to improve the removal by meso-DMSA of mercury from rats.

Comparative in vivo lead mobilization of meso- and rac-2,3-dimercaptosuccinic acids in albino Wistar rats.

Comparison of the racemic and meso forms of 2,3-dimercaptosuccinic acid (DMSA) in lead mobilization from lead-loaded albino Wistar rats demonstrates that the racemic form is significantly more effective in reducing femur lead levels. After four oral doses at 0.5 mmol/kg, femur lead levels were reduced to 87% of control values by meso-DMSA and to 50% of control levels by rac-DMSA. Similarly, when the dose was increased to 1.0 mmol/kg, femur lead levels were reduced to 69% of control levels by meso-DMSA and to 45% of control levels by rac-DMSA. A similar pattern was found for renal lead levels. Brain lead concentrations were significantly lower in treated groups than in control groups, but no differences were found between rac- and meso-DMSA. Rac-DMSA is more soluble than meso-DMSA in acetonitrile, ethyl acetate, and ethyl ether. The partition coefficient of rac-DMSA in the n-octanol/water system was found to be about 2.8. These results indicate that rac-DMSA deserves further attention as a possible substitute for meso-DMSA.

Racemic-2,3-dimercaptosuccinic acid for inorganic mercury mobilization in rats.

The efficiency of racemic-2,3-dimercaptosuccinic acid (rac-DMSA) compared with meso-2,3-dimercaptosuccinic acid (meso-DMSA) in mobilizing inorganic mercury was evaluated in female rats. Chelators were administered orally at a dose of 0.5, 1.0 or 2.0 mmol kg-1 on four consecutive days, 5 days after a single intraperitoneal 203Hg injection (with 0.5 mg HgCl2 kg-1). Both chelators reduced 203Hg retention in whole body and kidney and at higher doses also in the liver. Racemic-DMSA was more efficient at lower dose levels and equal to meso-DMSA at the highest dose level. Kidney retention decreased after rac-DMSA to 27, 10 and 10% of controls and after meso-DMSA to 68, 39 and 10% of control values at the 0.5, 1.0 and 2.0 mmol kg-1 dose level, respectively. Since meso-DMSA is already approved for human use, its stereoisomeric form, rac-DMSA, deserves further attention for treatment of mercury poisoning.

Biomarkers of heavy metal reproductive effects and interaction with essential elements in experimental studies on female rats.

Experimental studies in laboratories in Croatia and U.S.A. were conducted on female rats exposed to lead or cadmium to evaluate effects on the female reproductive integrity. The health condition of the offspring and relationship with essential elements were also evaluated. By using simple biomarkers of reproductive effects it was found that subchronic oral exposure to lead (1500-5500 ppm) or cadmium (50 ppm) during pregnancy and lactation decreased pup body weight, and that lead also decreased pup viability. Acute exposure to cadmium (3 or 5 mg/kg body weight s.c.) in vivo suppressed serum concentrations of progesterone and estradiol depending on the reproductive stage. Organ accumulations of lead or cadmium were accompanied by changes in the concentrations of iron and zinc in both mother and pups. Future research should focus on the effects of metals on endocrine disruption in the ovary and placenta, and on concomitant interaction of toxic and essential metals in mother and offspring.

Combined treatment with a new biscarbodithioate C9G2DTC and BGDTC for mobilizing cadmium deposits in rats.

The cadmium mobilizing efficiency of a combined treatment with a novel cadmium chelating agent disodium N,N'-bis(D-glucosyl)-1,9-nonanediamine-N,N'-biscarbodithioate++ + (C9G2DTC) and with sodium N-benzyl-D-glucamine-N-carbodithioate (BGDTC) was evaluated in albino rats. They received 109Cd intraperitoneally once and 1 week later chelation therapy six times over 12 days at 2-day intervals. The treatment groups were: 1, control; 2, BGDTC six times; 3, C9G2DTC six times; 4, C9G2DTC three times followed by BGDTC three times; 5, C9G2DTC twice followed by BGDTC four times; 6, C9G2DTC once followed by BGDTC five times. The radioactivity in liver, kidney and brain was determined 19 days after 109Cd administration. Results were expressed as a percentage of the 109Cd dose and differences were analyzed by Duncan's multiple range test (P < 0.05). Treatment with C9G2DTC resulted in higher Cd reduction in the liver and lower in the kidney than with BGDTC, which is in agreement with our previous findings. Combined treatment resulted in a greater reduction of Cd in the liver and kidney than by using either chelating agent alone, irrespective of the number of C9G2DTC or BGDTC treatments, and without causing redistribution to the brain. The important aspect of this work is that C9G2DTC--the novel cadmium chelating agent which is extremely efficient in reducing Cd liver deposits and about three times more toxic than BGDTC--has to be used only once at the beginning of the treatment to obtain optimal reduction of aged organ cadmium deposits.

In vivo cadmium mobilization by three novel bis(carbodithioates).

Four novel cadmium-chelating agents N,N'di(D-glucosyl)alkanediamine-N,N'-bis(carbodithioates) 4a-e were prepared as disodium salts of the general formula (CH2)n[N(CS2Na)CH2(CHOH)4CH2OH]2, where n = 7, 8, 10, and 12. They were synthesized by the reductive coupling of 2 mol of alpha-D-(+)-glucose (1) with 1 mol of the corresponding alkanediamines 2a-e followed by reaction with CS2 in a basic medium. The elemental analyses of the Cd complexes 5a, b, d, and e prepared revealed that these bis(carbodithioates) form 1:1 complexes with Cd2+. The in vivo cadmium-mobilizing efficacy of three of the new chelators (4a, b, and d) was determined in rats pretreated ip with CdCl2.H2O containing 2 microCi of 109Cd (74 kBq), and comparable data were obtained on a previously reported member of this series (4c, n = 9), and with BGDTC (sodium N-benzyl-D-glucamine-N-carbodithioate, 6), all given once at 1.0 mmol/kg ip. The compound with n = 12 (4e, C12G2DTC) proved to be too toxic in the preliminary study and was not evaluated further. A single injection of the 4a, b, and d caused a reduction in Cd levels of the whole body to ca. 50% and liver to ca. 12% of control levels. Comparable experimental data on BGDTC resulted in a reduction of whole-body cadmium to only 78% of the control levels and a reduction in liver cadmium to only 56% of control. After one and six injections at the same dosage, the new chelators (4a, b, and d) and C9G2DTC (4c, n = 9) significantly surpassed BGDTC for whole-body and liver Cd depletion but caused only a very modest depletion of renal Cd. While these compounds were designed to allow the two dithiocarbamate groups to coordinate to the same Cd2+ in vivo, the data do not prove that the two > NCS2Na groups bind to the same cadmium ion in vivo. The very rapid reduction in liver cadmium levels following only a single injection indicates that these -2 anions rapidly gain access to intracellular hepatic sites by some transport system.

Prolonged oral treatment with two monoesters of meso-2,3-dimercaptosuccinic acid for depleting inorganic mercury retention in suckling rats.

Two monoesters of meso-2,3-dimercaptosuccinic acid (DMSA), monoisoamyl meso-2,3-dimercaptosuccinate (Mi-ADMS) and mono-n-hexyl meso-2,3-dimercaptosuccinate (Mn-HDMS) were compared to DMSA in their efficiency to mobilize 203Hg in mercury-laden suckling rats. Seven-day-old pups were given 203Hg (18.5 kBq) with a dose of 0.5 mg Hg/kg/day as HgCl2 for five days. Seven days after the beginning of Hg loading a ten-day oral treatment with DMSA, Mi-ADMS, or Mn-HDMS was administered at a dose of 0.25 mmol/kg/day. At the end of experiment, radioactivity was measured in the whole body, liver, both kidneys, and brain. Monoesters of DMSA were superior to DMSA in decreasing body and organ Hg retention. The highest reduction in comparison to controls in groups treated with DMSA, Mi-ADMS, or Mn-HDMS occurred in the kidneys (48%, 97%, and 96%), followed by reduction in the liver (24%, 84%, and 83%), and in the brain (8%, 23%, and 23%, respectively). For both, Mi-ADMS and Mn-HDMS, the reductions in the whole body and organs were significantly greater than in controls or DMSA-treated rats. No difference between the efficiency of the two DMSA-monoesters was found.

Monoisoamyl and mono-n-hexyl meso-2,3-dimercaptosuccinate in mobilizing 203Hg retention in relation to age of rats and route of administration.

Monoisoamyl (Mi-ADMS) and mono-n-hexyl (Mn-HDMS) monoesters of meso-2,3-dimercaptosuccinic acid (DMSA) were given orally or parenterally for the mobilization of inorganic mercury in suckling and older rats. Chelators were administered at a dose of 2 x 0.5 mmol kg-1 on two consecutive days 2 weeks after a single 203Hg injection. Six days later, whole-body, kidney, liver and brain radioactivities were determined in gamma scintillation counters. Both Mi-ADMS and Mn-HDMS were found to be superior to DMSA in mobilizing mercury from body and organs. The results were similar after oral or parenteral treatment. The efficiency of both monoesters was even higher in younger than in older rats. This is the first report on the mobilization of mercury from the body of sucklings under conditions of late oral treatment.

Reduction of lead retention by mono-3-methylbutan-1-yl meso-2,3-dimercaptosuccinate in suckling rats.

The mono-3-methylbutan-1-yl (monoisoamyl) ester of meso-2,3-dimercaptosuccinic acid (Mi-ADMS) was previously found to be superior to meso-2,3-dimercaptosuccinic acid (DMSA) in mobilizing cadmium and mercury deposits in young and adult mice and rats. It was also tested to mobilize lead in and adult mice. It was also tested to mobilized lead in adult mice. The purpose of this study was to evaluate the ability of Mi-ADMS to chelate lead at a very young age, in sucking rats. Lead was applied intraperitoneally at the dose of 5 mg kg-1 in the form of lead acetate to six-day-old rats. Treatment with DMSA and Mi-ADMS was administered orally at the dose of 0.25 mmol kg-1, either as early (0.5 and 24 h) or a delayed (4th and 5th day after lead application) therapy. At the end of the experiment (6th day) lead was determined by atomic absorption spectrometry in the skeleton, liver, kidney and brain of the animals. Results showed that Mi-ADMS was more efficient than DMSA after early application in reducing the skeletal, kidney and brain content of lead. After delayed application it was either (skeleton and kidneys) or better (brain) than DMSA. There was no statistically significant influence of either chelator on liver lead content. The major finding is that Mi-ADMS at low doses causes a much higher reduction in brain retention of lead in sucklings than DMSA. This is important because the brain is considered to be the target organ of lead toxicity in the youngest age group.

Molecular-modeling design of cadmium-mobilizing agents: a novel biscarbodithioate.

This report describes the design, synthesis, characterization, and in vivo cadmium-mobilizing properties of a novel biscarbodithioate chelating agent, namely, disodium N,N'-diglucosyl-1,9-nonanediamine-N,N'-biscarbodithioate+ ++ (C9G2DTC), HOCH2(CHOH)4CH2(CS2Na)N(CH2)9N(CS2-Na)CH2( CHOH)4CH2OH, which can coordinate to a single cadmium ion with both of its carbodithioate groups (CS2Na) in its folded configuration. When evaluated for its cadmium efficacy at 1.0 mmol/kg x 5 ip in 109Cd-pretreated rats against sodium N-benzyl-D-glucamine-N-carbodithioate (BGDTC) as standard, the biscarbodithioate was found to reduce the whole-body levels of cadmium more rapidly in the rat than BGDTC which contains only one CS2Na group. The whole-body Cd depletions after the first ip injection of the new and the standard compound were 52% and 23%, respectively. The C9G2DTC was found to be more effective in removing cadmium from the liver (% Cd reductions compared to controls: C9G2DTC, 94, and BGDTC, 85), but slightly less effective in reducing renal cadmium levels (% Cd-reductions: C9G2DTC, 44, and BGDTC, 60). The ip LD50 of the bis-DTC was estimated to be slightly in excess of ca. 4.0 mmol/kg in the rat. A molecular model of this chelating agent indicates that, because of the flexibility of the nonane chain, both carbodithioate groups can approach closely enough to each other to permit complexation with the same cadmium ion to give a resulting structure without significant strain. A mechanism for the removal of Cd from CdMT by C9G2DTC is also proposed.

Monoisoamyl meso-2,3-dimercaptosuccinate as a delayed treatment for mercury removal in rats.

Monoisoamyl meso-2,3-dimercaptosuccinate (Mi-ADMS) was found to be superior to meso-2,3-dimercaptosuccinic acid (DMSA) in decreasing the body burden of 203Hg in rats under conditions of early treatment. In this experiment Mi-ADMS was used as late treatment for mercury removal. Albino rats aged 6 weeks and 7-day-old sucklings received a single intraperitoneal injection of 203Hg (as nitrate). Two weeks later they were treated with DMSA or Mi-ADMS (0.25 mmole/kg bw) on two consecutive days. The radioactivity in the carcass (whole body after removal of the gastrointestinal tract), liver, kidneys and brain was determined by solid crystal gamma scintillation counting six days after chelation therapy administration (3 weeks after 203Hg application). Both chelators reduced the body burden of mercury compared to controls. The effect of Mi-ADMS was superior to DMSA treatment in older rats for decreasing carcass and kidney retention, and in suckling rats for decreasing carcass, liver, and kidney retention. They were equally effective in decreasing brain retention in older rats and had no effect on brain retention in sucklings. The efficiency of Mi-ADMS in reducing the body burden of mercury was generally higher than the efficiency of the DMSA treatment. Therefore, Mi-ADMS deserves further attention as a late treatment for mercury removal.

Superiority of Mi-ADMS to DMSA as parenteral treatment for decreasing mercury (203Hg) body burden in rats.

The efficiency of meso-2,3-dimercaptosuccinic acid (DMSA) and the monoisoamyl ester of meso-2,3-dimercaptosuccinic acid (Mi-ADMS) in decreasing 203Hg retention was evaluated in rats in relation to age and time of treatment. The experiments were performed on six-week- and seven-day-old Wistar rats, which received 203Hg by intraperitoneal administration. The chelators DMSA or Mi-ADMS were also administered intraperitoneally, twice, on two consecutive days, in doses of 0.25 mmol/kg body weight as early (0.5 and 24 h) or delayed treatment (24 and 48 h, or 48 and 72 h) after 203Hg administration. The retention of 203Hg was determined in the carcass, liver, kidneys and brain six days after administration using gamma scintillation counters (double crystal, well type). In all experimental conditions, regardless of the animals' age and time of chelation therapy, Mi-ADMS was found to be superior to DMSA in reducing the body burden of 203Hg in whole body and organs. Mi-ADMS therefore seems to be a very promising chelator in the treatment of mercury poisoning.