Inorganic mercury exposure, mercury-copper interaction, and DMPS treatment in rats.

The aim of this study was to evaluate the efficiency of oral treatment with sodium 2,3-dimercaptopropane-1-sulfonate (DMPS) on reducing mercury deposits in rat kidney after chronic exposure to inorganic mercury. The effect on kidney copper levels was also evaluated. The results showed that after two months of exposure to 50 ppm of mercury (as mercuric chloride) the concentration of mercury in the kidney was 124 micrograms/g wet tissue. At the same time copper concentration rose from 11 to 77 micrograms/g. DMPS treatment caused 2- and almost 4-fold reduction of mercury and copper, respectively. This study demonstrates that chronic exposure to inorganic mercury may alter metabolism of copper and that DMPS is an effective means for reduction of both mercury and copper.

Influence of some factors on cadmium pharmacokinetics and toxicity.

Cadmium metabolism in the young and in conditions of dietary contamination with ash from coal gasification were investigated. The experiments were performed in adult rats which received ash in the diet (5%) and/or cadmium in drinking water (100 ppm) over a period of five weeks and in sucklings whose mothers were given the same treatment throughout pregnancy and lactation. In pharmacokinetic studies, (115m)Cd was administered orally or intraperitoneally to determine the intestinal absorption, retention, and distribution. Cadmium toxicity (LD(50)) was determined in different age groups of animals treated with ash for five weeks before a single oral or intraperitoneal administration of cadmium chloride. After intraperitoneal administration, (115m)Cd body retention decreased with age and was independent of the dietary treatment. Sucklings had a higher retention in the blood, carcass, and gut than adults. After oral administration, sucklings had a much higher body retention than adults regardless of the dietary treatment of their mothers. Cadmium toxicity was also independent of the dietary treatment. Most striking was a very high oral toxicity of cadmium in sucklings. It is concluded that the young might be at a special risk at the same level of environmental cadmium exposure because of the high oral cadmium toxicity at this age which is most probably due to a high cadmium retention in the gut. It is also concluded that the mixture of elements contained in ash is not likely to influence cadmium metabolism and toxicity in conditions of dietary exposure.

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.

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.

More data on mercury absorption in relation to dietary treatment in rats.

The kinetics of mercury (Hg) absorption in relation to diet by determining whole body (WB), carcass (C) and gut (G) retention in control and milk-fed rats 6, 9, 12 and 15 days after oral administration of 203Hg have been studied. All retention values were higher in the milk-fed than in control rats during the experimental period. The higher WB retention in the milk-fed animals was primarily due to increased G retention especially at shorter time intervals. Animals on the milk diet had in the C, higher retention values, and in the G, higher retention and longer residence time. There was no evidence that Hg from the gut compartment entered into other parts of the body within the observation period. More evidence is needed about the effect of other dietary treatments on Hg metabolism.

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.

Comparison of dry and wet ashing procedures for cadmium and iron determination in biological material by atomic-absorption spectrophotometry.

A possible loss of cadmium and iron from the sample during dry ashing of the kidney, liver or carcase was examined by the radioactive isotope labelling technique. Cadmium-115 m or iron-59 was administered to rats 4-7 days before the rats were killed and samples collected. Dry ashing in different types of dishes and wet digestion with nitric acid were compared. There was no loss of cadmium or iron by volatilization during dry ashing at 600 degrees or 450 degrees respectively, but a significant amount of iron was bound on glass or porcelain crucibles. Storage of ashed and dissolved samples (in 10 nitric acid) did not show any change of cadmium or iron concentration up to 9 days.

Elimination of mercury from amalgam in rats.

The aim of this study was to measure the urinary mercury excretion in rats exposed to amalgam over a two months period. Animals were either exposed to mercury from 4 dental amalgams or fed the diet containing powdered amalgams. The results showed significantly higher mercury amount in urine of both exposed groups than in control. Even two months after the amalgam had been placed in rats teeth, the amount of mercury in the urine remained 4-5 times higher than in control, and 4 times higher than in rats exposed to diet containing powdered amalgam. The elevated urinary Hg amount was accompanied by an increased level of total protein in urine. In the same exposure period the excretion of total protein in urine of rats with amalgam fillings was 2 times higher than in control and 1.5 times higher than in rats exposed to amalgam through diet. Concentrations of mercury in the sera of all groups were below the detection limit of the method. The results show that amount of mercury and protein in the urine of rats were related to the mercury release from dental malgam.

Chronic and reproduction studies in rats exposed to gasifier ash leachates.

Ash from the coal gasification process contains a broad spectrum of elements which through leaching (gasifier ash leachates) may enter into the environment. The health effect of such leachates i.e. complex mixtures of inorganic elements is insufficiently known. We investigated the effect of gasifier ash leachates in a chronic-(9-month) and in a three-generation reproduction study. The leachates were prepared weekly by water extraction of ash from a Lurgi coal gasification plant in Yugoslavia, and given to experimental animals instead of drinking water. In the chronic experiment exposed animals showed no changes in mortality rate, haematological findings, concentration of Fe, Zn, Mn in kidneys, liver, testicles and femur, as well as in femur composition and morphometry, gross pathology and organ histology. In the reproduction study the number of pregnancies, weight and number of newborns, and concentration of Fe, Zn, Mn in carcasses of sucklings were the same in control and experimental animals.

Simultaneous reduction of radioactive strontium, caesium and iodine retention by single treatment in rats.

The effect of a mixture of calcium alginate, iron (III) ferrocyanide and potassium iodide added to rat diet on 85Sr, 137Cs and 131I metabolism and health was investigated in female rats after four weeks of treatment. The retention of these radioisotopes was determined in the whole body and critical organs six days after 85 Sr and 137CS and one day after 131I oral administration. The health effect of the mixture was evaluated by measuring body weights, haematological parameters, concentrations of iron, zinc and manganese in the kidneys, liver and femur, bone parameters (femur composition and morphometry) and by a histopathological examination. The mixture reduced 85Sr retention in the femur 11 times, 137Cs retention in the thigh muscle 102 times and 131I retention in the thyroid 134 times. Treated animals were in good health and the only differences found between the control and experimental rats were slightly lower haemoglobin values in the blood and a slightly lower iron concentration in the liver. It is concluded that the mixture was very efficient for decreasing body retention of three important fission products and that it can be used over long periods without causing adverse health effects.

Interaction of lead with some essential elements in rat's kidney in relation to age.

The aim of this study was to evaluate the interaction of lead given orally with Fe, Zn, and Cu in adult female rats and in their pups. Kidney was chosen for studying this interaction. Four different doses of lead (acetate) from 1500 to 7500 ppm were administered to mature female albino rats in beverages during 6 wk. The exposure lasted from mating up to 3 wk after delivery. Pb, Fe, Zn, and Cu were determined in kidneys of mothers and pups. Histopathological examinations were also performed. Results showed significantly lower concentrations of Fe, Zn, and Cu in kidneys of mothers on all lead levels. Their pups showed no change in concentrations of essential elements and even increased Fe at the highest exposure level. Concentrations of Pb and histopathological changes in the kidney were similar in mothers and offspring, although pups received only a fraction of the mothers' doses. Our results indicate that in immature animals the interaction of Pb with essential elements in the kidney is different from that in their mothers.

Uptake of cadmium, copper, iron, manganese, and zinc in mushrooms (Boletaceae) from Croatian forest soil.

The concentration of trace elements (Cd, Cu, Fe, Mn, and Zn) was measured in different species of mushrooms (Boletaceae) and correlated with corresponding elements in soil. Five different species of Boletaceae mushrooms and soil samples were collected from forests of Varazdin county in Croatia. Trace elements were analyzed by atomic absorption spectrometry in mushrooms and in EDTA-extracted soil. The results showed that Cd, Cu, and Zn are concentrated in mushroom tissue from soil with transfer factors (mushroom/soil) of 27.0,10.5, and 12.5, respectively. Cadmium incorporated much less in Leccinum (mean 0.73 mg/kg dry weight) than in Boletus, Xerocomus, or Gyroporus (respective means, 6.8, 8.4, and 12.3 mg/kg). Copper and Zn were accumulated in all collected mushrooms (14.7-35.6 and 109-179 mg/kg, respectively) with no difference among species. There was no accumulation of Fe and Mn in mushrooms, but concentrations differed between species, with lowest values in Leccinum. Iron varied from 31 to 878 mg/kg and Mn from 2.9 to 409 mg/kg. Correlations between elements in mushrooms and soil were significant only for Mn. Because no significant correlations for Cd, Cu, Zn, and Fe between mushrooms and soil were found, more studies are needed with only one species of mushrooms collected at locations with different levels of soil contamination. In spite of higher concentrations of Cd in some Boletaceae species, it is assumed that Cd intake through moderate mushroom consumption remains below suggested Provisional Tolerable Weekly Intake (FAO/WHO).

Dietary calcium and blood lead levels in women.

Nutritional factors are known to influence metabolism and toxicity of several metals in animal experiments, but relevant human data are scarce and inconclusive. In this work, we tested the hypothesis that dietary calcium influences lead metabolism in humans. Blood lead concentrations were used as indicators of lead exposure and metabolism. Two groups of peasant women living in similar conditions in two different regions in Yugoslavia (100 in each) were chosen as subjects for this purpose. In region A, the dietary calcium intake was about 940 mg, and in region B about two times lower, i.e., 450 mg/day. The average blood lead concentration was significantly lower in women from region A (69 micrograms/L) than from region B (83 micrograms/L). Our results support the assumption that adequate calcium intake might be one of the preventive measures for decreasing lead absorption. This new evidence, sought for some time by nutritionists and toxicologists, needs further international confirmation.

Lead, cadmium, and mercury dietary intake in Croatia.

This paper gives an overview of published data on levels of lead, cadmium, total and methyl-mercury in various food items, and of a daily dietary intake assessment in Croatia focusing on the last 10 years. It briefly describes the most reliable methods for quantitative analysis of lead, cadmium, and mercury in biological material. Lead and cadmium concentrations in vegetables and in organs of domestic animals refer to non-exposed rural areas. Mercury concentrations in fish and mussels refer to industrially polluted and non-polluted areas of the Adriatic. The daily dietary intake of lead and cadmium was assessed on the basis of duplicate-diet-collection and food-disappearance method. The assessment of the total and methyl-mercury dietary intake was based on dietary surveys of family seafood consumption. Lead and cadmium intake through food in the general population was 6-40% of the Provisional Tolerable Weekly Intake (PTWI), depending on the assessment method. The only Croatian population consuming more mercury through seafood is the one living in Dalmatia, approaching the PTWI defined by WHO.

Comparison of two methods for destruction of biological material for determination of selenium.

The purpose of the study was to compare two methods for destruction of biological material for selenium (Se) analysis: wet digestion by conductive heating in programmed digestion block and digestion in microwave oven. In both methods samples were prepared in a closed system using nitric acid. Selenium was analysed by electrothermal atomic absorption spectrometry. The results have shown that both methods are convenient for complete mineralisation and are accurate in determining selenium in a variety of foodstuffs. Microwave digestion, however, has the advantage of speed and simplicity over the conventional heating procedure.

Comparison of two extraction procedures for determination of trace metals in soil by atomic absorption spectrometry.

The study compares nitric acid and ethylenediaminetetraacetic acid (EDTA) extraction of forest soils for the analysis of trace metals Fe, Mn, Zn, Cu, Pb, and Cd. Fifty forest soil samples from ten different locations were extracted using both methods. The two extraction procedures were compared through regression analysis for each element. All elements were analysed by flame atomic absorption spectrometry method (AAS). The results show that both extracting procedures are only partially effective for most of the measured trace elements in soil. The extraction with diluted HNO3 was incomplete, as large amounts of siliceous material remained undigested. Recoveries obtained by this method for Fe, Mn, Zn, Cu, Pb, and Cd on certified reference material (San Joaquin Soil) were 34, 79, 47, 56, 71, and 102%, respectively. EDTA extraction was even less effective and is considered to reflect the quantity of bioavailable metals. The respective recoveries were 2, 45, 7, 20, 38 and 74%. The regression analyses performed for EDTA-extractable vs. HNO3-extractable metals of forest soils showed high and significant correlation for all examined metals, except Fe.

Validation of microwave digestion method for determination of trace metals in mushrooms.

A microwave digestion method for mushrooms, developed in the study, allows fast preparation of samples and reduces the contamination risk in the process of determining trace metals. Concentrations of six trace elements, Fe, Mn, Cu, Zn, Pb, and Cd were measured in 50 samples of different species of edible mushrooms (fam. Boletaceae) using atomic absorption spectrometry after microwave and dry ashing procedure. The methods were validated through certified Standard Reference Material SRM 1577b (Bovine Liver) which was treated and analysed using the same procedures as for the mushrooms. The samples were either digested with concentrated HNO3 in closed Teflon PFA vessels in a microwave oven, or ashed in quartz crucibles at 450 degrees C. The respective recoveries of Fe, Mn, Zn, Cu, Pb, and Cd obtained by measuring SRM were 112, 107, 104, 115, 111 and 95% after microwave digestion procedure and 86, 101, 109, 111, 98, and 110% after dry ashing procedure. The correlation between concentrations obtained by the two different methods of sample preparation was high for all metals.

Decomposition of fish samples for determination of mercury.

The aim of the study was to compare the efficiency of acid and alkaline decomposition of biological materials using an open and a closed system for total mercury determination. Acid digestion was performed with concentrated HNO3 in tubes at 80 degrees C and lasted five hours. Alkaline digestion was performed with a 45% NaOH and a 1% cysteine, heated at 120 degrees C for 20 minutes. Total mercury was measured by atomic absorption spectrometry using the cold vapour technique (CVAAS). The average recovery obtained for analysis of certified reference material in closed tubes for acid digested sample was superior to the alkaline one, 103 +/- 4% vs. 70 +/- 3%, respectively. In addition, the recoveries through the open system acid digestion (90 +/- 8%) and the open system alkaline digestion (57 +/- 2%) were lower than through the respective closed system digestions. Reproducibility of the acid decomposition method was superior to the alkaline one.

Comparison of two methods using atomic absorption spectrometry for determination of selenium in food.

This study describes and compares two methods of atomic absorption spectrometry (AAS) for the selenium (Se) analysis in food: electrothermal AAS (ET AAS) and hydride generation method of AAS (HG AAS). The accuracy of the two methods was established by analysing two biological reference materials: Wheat Flour 1567a and Bovine Liver 1577b from the National Institute of Standards and Technology, USA. Good agreement with certified values was obtained for both methods. The accuracy of ET AAS method is 109% and 103% for Wheat Flour and Bovine Liver, respectively. The respective accuracies for HG AAS method were 88% and 87%. The detection limit obtained for ET AAS was 1 microgram Se/L and for HG AAS 0.02 microgram Se/L. The repeatability of ET AAS method was 5-11% and that of HG AAS 14-17%. Both methods are similar in accuracy and repeatability, but hydride generation (HG AAS) is more sensitive than graphite furnace technique (ET AAS) for determination of selenium in food.

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.