Abstract
Exposure to environmental lead remains a widespread problem in most industrialized countries. Usage of modern agents purposed for elimination of heavy metals as well as for therapy and prevention of chronic poisoning does frequently result in toxic signs. Dietary nonstarch polysaccharides were suggested to be effective when used for this purpose. The present study was conducted to estimate metal binding capacity and effects of calcium salts of pectate and alginate on lead absorption, distribution, and removal with feces. Under in vitro conditions calcium alginate showed the highest lead-binding capacity in comparison with other agents studied. Metal binding capacity of calcium pectate was slightly lower. In rats simultaneous administration of lead acetate and suspensions containing calcium alginate or calcium pectate prevented metal absorption and significantly reduced lead accumulation in inner organs and femur. In experiments estimating lead removal from inner organs and femur in rats preliminary exposed to the heavy metal, calcium alginate and calcium pectate were the most effective agents studied in comparison with others, as indicated by reduced lead concentration in organs and femur as well as increased metal content in feces of laboratory animals. The results suggest that calcium pectate and calcium alginate may be considered perspective dietary compounds purposed for prevention and treatment of chronic lead poisoning.
Lead is a ubiquitous environmental pollutant that poses a serious threat to human health. For example, in the USA more than one million construction workers are exposed to excessive amounts of lead and other heavy metals (Levin and Goldberg 2000). The greater concern is to the high vulnerability of children to lead exposure even in small quantities. In the USA alone approximately 500,000 children aged 1 to 5 years (4.4% of children this age) were found to have elevated blood lead level (Rogan and Ware 2003). The main sources of lead in man’s environment are diet, lead-based paint in older housing, lead in soil and dust around industrial and mining areas, and continuing use of leaded gasoline in some countries (Paoliello and De Capitani 2005; Viard et al. 2004).
Excessive exposure to lead ions results in the metal entering a human body through the digestive path, lung inhalation, and skin, and provoking damage of almost all organs and systems, in particular, the central nervous system, immune system, kidneys, adrenals, and bones (Markowitz 2000). Generally the mainstays of therapy consist of the elimination of all sources of exposure, nutritional support, and the therapeutic use of specific chelators for binding of metal ions and removal of them from the body with urine or feces (Kalia and Flora 2005). Unfortunately up-to-date chelators cannot be used for a long treatment of chronic poisoning with lead due to their toxic effects on various organs and systems as well as on mineral balance (Smith et al. 2000). So new substances suitable for treatment and prevention of lead poisoning should be found.
At present attention is given to a group of substances called dietary fibers, including pectins, alginates, chitin and chitosan, carrageenans, lignin and some others, which were shown to exert beneficial influence on different organs and systems and have a capacity to bind heavy metals (Krauss et al. 2001). Alginates and pectins belong to different natural sources such as brown algae and higher plants, respectively. But both of them were shown to possess a high affinity to the lead ions (Kartel, Kupchik, and Veisov 1999).
Pectins are the ionic plant polysaccharides, which are widely used in the food industry because of their gelling and thickening properties (Thakur, Singh, and Handa 1997). The main structural features of pectin are the linear chains containing more than 100 (1–4)-linked α-
A number of studies confirm that pectin and alginate salts exert beneficial health effects related to their binding activity such as reduction of serum cholesterol levels (Gonzalez et al. 1998), enhanced fecal bile acid excretion (Garcia-Diez et al. 1996), hepatoprotective activity (Khotimchenko et al. 2004a), and interaction with metal ions (Jodra and Mijangos 2001; Kartel, Kupchik, and Veisov 1999).
In this study we estimated the influence of insoluble calcium salts of pectin and alginate on absorption of lead in intestine, its removal from inner organs and bones, and its excretion with feces. We compared the effects of pectin and alginate salts with those of lignin and activated charcoal. Lignin was shown to effectively interact with the lead ions, exhibit good absorption capacity, and may be recommended for removal of heavy metals from waste water and from living organisms (Demibras 2004). Administration of activated charcoal is currently regarded as the most effective means of reducing the systemic absorption of many ingested poisons including heavy metals (Babel and Kurniawan 2003).
Before conducting experiments on lead kinetics in rats, we determined a lead binding capacity of calcium pectate, calcium alginate, lignin, and activated charcoal under in vitro conditions.
MATERIALS AND METHODS
Polysaccharide Samples Preparation
High-esterified citrus pectin without additives was obtained from Copenhagen Pectin A/S, Lille Skensved, Denmark. The stated degree of esterification of this preparation was 60.0%. The pectin preparation contained no acetyl or amide groups. Initially pectin with a degree of esterification of approximately 1.2% was prepared. During this process 100 g of high esterified citrus pectin was de-esterified in 1600 ml 50% ethyl alcohol containing 20 g NaOH and 20 g KOH (30 min at 20°C). After acidification, pectin was isolated from ethanol by filtration. For the preparation of calcium pectate 100 g of low-esterified pectin was suspended in 500 ml 70% ethanol. Gradually 100 ml of 70% ethanol solution containing 22.6 g CaCL2·6H2O was added. After the process was finished calcium pectate was separated through a glass filter, rinsed with 800 ml 70% ethanol, and dried at 60°C.
Sodium alginate (type HV) without additives was obtained from Kelco (California, USA). Calcium alginate was prepared as follows. 200 g of sodium alginate was suspended in 1000 ml of 70% ethanol. Shaking intensively, 8 g of CaCl2·6H2O diluted preliminary in 100 ml of 70% ethanol were added. Calcium alginate obtained was separated with a porous glass filter with a mesh of 40 μm, rinsed with 500 ml of 70% ethanol, and dried at 60°C.
Granulated lignin was obtained from Saintec, Russia, under the trade mark Polyphepan, which is approved as the agent for therapy of chronic and acute heavy metal poisoning. Tablets of activated charcoal were obtained from Irbit, Russia. The tablets were ground to a powder before being used in experiment.
Sample Analysis
The galacturonan content of the pectin preparation was determined colorimetrically by the m-hydroxydiphenyl method (Blumenkrantz and Asboe-Haunsen 1973). The degree of esterification was characterized using titrimetric analysis (Afanasyev et al. 1984). Intrinsic viscosity of low-esterified pectin was determined in 0.05 M NaCl/0.005 M Na-oxalate at 25.0°C and pH 6.0 using an Ubbelohde viscosimeter. The intrinsic viscosity was related empirically to the molecular weight by the Mark-Howink relation (Kravtchenko and Pilnik 1990). The calcium content in the calcium pectate sample was assayed by atomic absorption and expressed in mg/g and mg-equivalents/g of sample (Kostecka 2000).
The uronic acid content of original sodium alginate and prepared calcium alginate was determined colorimetrically by the m-hydroxydiphenyl method and expressed in percent (Blumenkrantz and Asboe-Haunsen 1973). The calcium content in the calcium alginate sample was assayed by atomic absorption as described above. The ratio of carboxyl groups forming a calcium salt was calculated as a calcium:uronic acid content ratio expressed in mg-equivalents/g. Intrinsic viscosity of original sodium alginate was determined in 0.05 M NaCl/0.005 M Na-oxalate at 25.0°C and pH 6.0 using an Ubbelohde viscosimeter. The intrinsic viscosity is related empirically to the molecular weight by the Mark-Howink relation (Kravtchenko and Pilnik 1990).
Estimation of Lead-Binding Capacity
Investigation of the binding capacity of polysaccharide samples and activated charcoal was carried out in a test tube containing a 1000 ml of 2×10–3 M lead acetate solution. To this was added 500 mg sample of the compound studied. The period of interaction was 24 h. Controlled pH of the medium was 5.0, temperature of solutions was 20°C, and speed of steering was 400 rpm. After 24 h the lead solution with the samples of polysaccharides or activated charcoal was filtered and lead quantity was determined in the supernatant fluid using titrimetric method with EDTA. Lead binding capacity was calculated as difference between lead concentrations in the initial solution and in supernatant fluid.
Animals and Diet
Male Wistar rats were obtained from Pacific Institute of Bioorganic Chemistry (Vladivostok, Russia). The rats weighing 130 to 160 g, were housed in stainless steel wired cages (in groups of four per cage) and kept in an isolated room at a controlled temperature 20°C to 22°C and ambient humidity 60% to 65%. Lights were maintained on an artificial 12-h light-dark cycle. Animals were first adapted to the facility for 1 week and provided with water and standard feed ad libitum. The composition of the standard diet was as follows (g/l00 g): casein, 21.0; cellulose, 5.3; sunflower oil, 7.0; cholesterol, 1.0; sucrose. 15.0; starch, 45.9; methionine, 0.3; minerals, 3.5; and vitamin mixture, 1.0. All animal experiments were conducted in accordance with the guide for the care and use of laboratory animals of Vladivostok State Medical University, which is following the Guiding Principles in the Use of Animals in Toxicology.
Experimental Design
The whole study consisted of the three experiments estimating influence of calcium pectate and calcium alginate, lignin, and activated charcoal samples on lead absorption in intestine, lead removal from inner organs and bones, and lead elimination with feces, respectively.
In the first experiment after adaptation period the 60 rats were randomly divided into six groups of 10. These groups consisted of a control group, and five groups that received lead (“Pb,” “Pb + Ca alginate,” “Pd + Ca pectate,” “Pb + Lignin,” “Pb + Activated charcoal”). All groups were fed the standard diet. The control group received daily 1 ml of distilled water by gastric gavage. Animals of other groups were daily given by gastric gavage 1 ml of lead acetate solution containing 50 mg of Pb per kg. One hour later animals of the groups “Pb + Ca alginate,” “Pd + Ca pectate,” “Pb + Lignin,” and “Pb + Activated charcoal” were given by gastric gavage a suspension containing calcium alginate, calcium pectate, lignin, and activated charcoal, respectively, in a dose 0.1 g/kg. To prevent interaction of lead and the samples with food components, animals of all groups were not given access to food for 1 h after the administration of metal and polysaccharide or activated charcoal. After 18 days of experiment, all animals were given light ether anesthesia and killed by decapitation. Liver, kidneys, heart, and femora were removed, weighed, rinsed, and stored until analysis. The experiment was repeated using calcium pectate, calcium alginate, lignin, and charcoal in a dose of 0.5 g/kg for 21 days following the design described before.
In the second experiment after the adaptation period, 80 rats were randomly divided into six groups. The first two groups, “Control” and “Pb” contained 20 animals each; the other groups contained 10 rats. All groups were fed the standard diet. The control group received daily 1 ml of distilled water by gastric gavage. Animals of other groups were daily given by gastric gavage 1 ml of lead acetate solution containing 50 mg of Pb per kg. On day 22 administration of lead was ceased. A half of the rats of “Control” group and “Pb” group were killed by decapitation under slight anesthesia; inner organs and femora were removed, weighed, rinsed, and stored until analysis. For the next 21 days the remaining rats of “Control” and “Pb” groups were given only standard diet whereas rats of other groups (“Pb + Ca alginate,” “Pd + Ca pectate,” “Pb + Lignin,” “Pb + Activated charcoal”) were daily administered suspensions containing polysaccharide and activated charcoal samples 1 h before feeding as described before. Then after a week, during which all animals were given the standard diet only, the rats were killed and inner organs and femora were removed, weighed, rinsed, and prepared for lead analysis as described before.
In the third experiment 35 rats were randomized into six groups. In “Control” group were five rats, other groups contained six rats each. All groups were fed the standard diet. The control group received daily 1 ml of distilled water by gastric gavage. Animals of other groups were daily given by gastric gavage 1 ml of lead acetate solution containing 100 mg of Pb per kg for 2 weeks. Then administration of lead was discontinued and all rats were put into individual cages. For the next 7 days all groups were fed standard diet and at the same time rats of the groups “Pb + Ca alginate,” “Pd + Ca pectate,” “Pb + Lignin,” and “Pb + Activated charcoal” were additionally given 1 h before feeding through gastric gavage water suspensions containing 0.5 g per kg of the samples with calcium alginate, calcium pectate, lignin, and activated charcoal. Collection of feces was performed daily. Excreted feces were dried, ground and prepared for the lead analysis.
Metal Concentration Analysis
Lead concentration in solution filtered in a course of the in vitro studies on lead binding capacity of polysaccharides and activated charcoal was assessed using a titrimetric method with EDTA. The lead content in heart, kidney, liver, and femur removed from the rats as well as in feces was estimated by atomic absorption spectrometry (Parsons and Slavin 1993).
Statistical Analyses
Findings indicating the lead contents in organs and bones are presented as mean ± SEM. Results obtained at the end of the study were analyzed using one-way analysis of variance (ANOVA), parameters of group “Pb” were compared with those of groups “Control,” “Pb + Ca alginate,” “Pd + Ca pectate,” “Pb + Lignin,” and “Pb + Activated charcoal” using post hoc Tukey’s test. Statistical evaluation of parameters of groups “Control” and “Pb” obtained in the second experiment estimating lead accumulation in inner organs and bones were performed using the two-tailed Student’s t test. Differences with a value of p < .05 were considered statistically significant.
RESULTS
Sample Characteristics
Chemical analysis of the calcium pectate sample showed the following results. The galacturonic acid concentration was 60.5%. The assay showed degree of esterification of the calcium pectate sample to be approximately 1.2%. The free and esterified carboxyl groups in the pectin macromolecules were distributed in a random pattern. Calculated molecular weight of the calcium pectate sample was approximately 20 kDa. 86% of carboxyl groups were presented in calcified form.
Analysis of the calcium alginate sample showed the following results. The uronic acid content found through the analysis was 77.3%. Calculated molecular weight of calcium alginate was approximately 403 kDa. 82.5% of carboxyl groups were presented in calcified form.
In Vitro Lead-Binding Capacity
In vitro experiment showed calcium alginate to have the maximum metal-binding capacity under given conditions in comparison with other agents studied. Calcium pectate bound markedly lower amount of lead ions, making up to 80% of the calcium alginate lead-binding capacity. Activated charcoal and lignin was 2.6 and 4.7 times less effective than calcium alginate (Figure 1).
Effects of Polysaccharides on Lead Absorption
These series of experiments showed that administration of lead acetate for 18 and 21 days results in dramatically increased metal contents in liver, heart, kidney, and femur bones in comparison with control group (Table 1). Simultaneous use of 0.1 g per kg of body weight of calcium alginate or calcium pectate along with lead acetate did significantly change these parameters. Liver lead content was 35.5% and 39.6%, respectively, lower. Metal content in heart as result of the use of calcium alginate and pectate was 40.6% and 46.0%, respectively, lower. Amount of lead in kidney was 26.8% and 35.5%, respectively, lower than in “Pb” group. Administration of calcium alginate did not result in significant changes in femur lead content whereas calcium pectate contributed to reduction of this by 26.4%. Usage of lignin and activated charcoal in a dose 0.1 mg per kg of body weight did not make any alteration in amount of lead stored in organs and femur of rats (Table 1). Calcium alginate as well as calcium pectate given in a dose 0.5 g per kg body weight contributed to more pronounced decrease of lead stored in inner organs and femur. In liver, lead contents were reduces by 41.6% and 43.1% for calcium alginate and calcium pectate usage, respectively. In heart, content of lead was lowered by 56.0% and 48.2%, respectively; in kidneys, by 53.9% and 58.3%, respectively. Administration of these polysaccharide samples significantly slowed accumulation of lead in bones, showing reduced lead contents in femur by 65.2% and 65.7%, respectively. Concentration of lead in inner organs and femora in rats given lignin did not significantly differ from that of untreated animals. Similar results were obtained in the group administered activated charcoal. There were no effects registered after the use of activated charcoal and lignin in a dose 0.5 mg per kg of body weight (Table 1).
Effects of Polysaccharides on Lead Removal from Inner Organs
In this study, as it was shown in previous experiment, 3 weeks’ administration of lead resulted in significant increase of lead concentration in inner organs and bones. In liver lead contents were 4.1 times higher, in heart 52.8% higher, in kidney almost 6 times higher, and in femur 8.3 times higher than in the “control” group. Within next 3 weeks the lead concentration was not significantly changed in inner organs and femur (Table 2). Both calcium alginate and calcium pectate contributed to metal removal from kidney. After the use of calcium alginate, the lead contents in kidney were reduced by 39.7%; after administration of calcium pectate it was 37.9% lower. In femur the lead quantity did not significantly changed as a result of the calcium alginate usage, but calcium pectate contributed to reduction of lead content in femur by 35.8%. In contrast, after administration of calcium alginate there was significant increase of lead content in liver and heart in comparison with animals of control group (413.8% and 206.6%, respectively) and even with animals given lead acetate and not treated with polysaccharides (39.2% and 102.1%, respectively). The same results describing lead concentration in liver and heart were obtained in experiments with calcium pectate. The amount of metal in liver was eight times higher compared with control group and 146.7% higher than in animals of “Pb” group. In heart the lead concentration was increased by 163% in comparison with the control group and by 108.2% in comparison with rats of “Pb” group not treated with polysaccharides.
Administration of lignin as well as activated carbon did not induce any alteration in lead concentration in liver, heart, kidney, and femora (Table 2).
Effects of Polysaccharides on Lead Removal with Feces
Fecal lead concentration was significantly higher in all groups of animals given the lead acetate solution compared to the control group. This indicates continuous lead elimination through the digestive tract. The use of calcium alginate in rats previously exposed to lead helped to increase the amount of lead being excreted with feces in comparison with the “Pb” group. The lead contents in feces of rats in this group were 14.8% more. Elimination of lead was more pronounced in animals treated with calcium pectate with fecal lead concentration 45.8% higher than in feces of untreated rats. The amount of lead in feces of rats given lignin and activated charcoal after lead exposure did not significantly differ from “Pb” group (Table 3).
DISCUSSION
Lead is a potential toxin possessing no physiological value. Entered in low doses it affects functions of organs, manifesting in lowered intelligence and behavioral problems (Lidsky and Schneider 2003), impaired immune system (Singh et al. 2003), altered growth and structure of bones and tooth dentine (Markowitz and Shen 2001), induced renal dysfunction (Brewster and Perazella 2004), and disturbed endocrine system (Baccarelli, Pesatori, and Bertazzi 2000). During the past 20 years there have been significant advances in the understanding of absorption, distribution, retention, and toxic effects of lead. Unfortunately, there is no accurate measure of total body lead; blood lead concentration reflects only a small proportion of the total body burden. The remainder is found in large part in bone and, to a lesser degree, in soft tissues such as brain, liver, and kidney, although differences in lead distribution have been observed at various stages of life (Markowitz 2000). The storage of the heavy metal in these organs contributes to their dysfunction.
The main purposes of medical treatment of patients exposed to lead include prevention of lead entering the human body and accelerated removal of stored metal from organs and bones as well as symptomatic therapy (Kalia and Flora 2005). Currently, the specific treatment of lead poisoning varies with the degree of intoxication. Generally the mainstays of therapy consist of the elimination of all sources of exposure, nutritional support, and the use of specific therapeutic chelators, which bind metal ions and remove them from the body with urine or feces. The number of approved medicines being used with such purpose is very few (Sillanpaa and Pirkanniemi 2001). Application of these drugs is not shown to be safe and is usually associated with some difficulties due to their toxic effects such as dyspeptic signs (Rogan 2000), allergic reactions (Klaassen 1996), renal dysfunction (Santiago et al. 1983), and mineral imbalance manifesting in reduced blood levels of calcium, iron, phosphorus, potassium, and magnesium (Smith et al. 2000). Because of this, chelating agents cannot be used for more than several weeks following an obligatory prolong recovery period. Hence, they rather can be applied for therapy of acute poisonings with lead or rare periodical treatment of chronic exposure. Taking into consideration the permanent influence of environmental heavy metals on people, the necessity of agents purposed for prevention of heavy metals entering human body and permanent elimination of them is of importance. These agents should not provoke mineral imbalance and damage of stomach and intestinal mucous, also they need to be safe for long-term usage. A group of substances conforming to these demands is dietary fibers. Some of these substances were shown to have a capacity of binding the ions of heavy metals (Rose and Quarterman 1987). The highest metal-binding capacity was found in experiments with pectin and alginate salts (Kartel, Kupchik, and Veisov 1999).
Dietary fibers are essential food constituents. Daily consumption of dietary fibers for average human is recommended as 30 g, e.g., approximately 0.5 g/kg (Krauss et al. 2001). So in our experiment we used the dose of polysaccharides 0.5 g/kg. The dose of lignin and activated charcoal recommended for removal of heavy metals is much smaller, but for relevant comparison of all substances we also used this dose in all groups of rats.
In our study we investigated the effects of calcium salts of pectin and alginate compared with those of lignin and activated carbon on lead absorption and removal in rats. Because lead toxicokinetics in humans and rats are similar, rats are a good model for studying lead metabolism and toxicity. Recommended dose for modeling of lead intoxication is 0.05 to 0.1 g/kg body weight, which was used in our study (Bogden 1997).
The results obtained through our study definitely indicate that nonstarch polysaccharide substances such as pectates and alginates may be successfully used for the purpose of lead removal. Calcium pectate and calcium alginate significantly reduced lead accumulation presumably by slowed absorption from the gastrointestinal tract. Also they markedly accelerated lead removal from kidneys and bones known as main organs of the metal storage.
Effects registered after experiments showed that calcium pectate and calcium alginate were more effective than lignin and activated charcoal used in the study. It is well known that binding process is dependent on factors of ambient medium such as pH, temperature, metal:sorbent ratio, and some others (Jang et al. 1990). So, presumably under conditions different from this experiment the results may alter. Taking into account considerable differences in binding capacities of pectate and alginate in comparison with lignin and activated charcoal, we assume these data to be similar under different conditions but it needs experimental conformation.
Influence of the compounds on retardation of lead absorption and its removal from the body corresponded with the results obtained in experiments carried under in vitro conditions. Calcium alginate and calcium pectate possessing higher binding capacity exerted most pronounced effects on lead kinetics in rats, whereas lignin and activated charcoal having low binding capacity did not significantly change any parameters of lead content in inner organs and femora as well as in feces.
Calcium salts of alginates were previously shown to have high metal-binding capacity regarding heavy metals and have been considered as effective agents for treatment of waste water (Jodra and Mijangos 2001). High metal-binding capacity of calcium alginate was demonstrated using an ion-exchange model and modified Langmuir model based on the conditions in the gel phase (Jang et al. 1990). These models suggest that the polysaccharide is effective in interacting with relatively high concentration of heavy metals and possesses very low metal-binding activity when the amount of metal is insignificant. During experiments of the present study, we obtained results indicating calcium pectate as well as calcium alginate do bind lead ions in rats and remove it through the digestive tract.
Comparison of effects exerted by calcium alginate and calcium pectate showed no differences, indicating the mechanism of binding activity to be the same. This is likely relating to sorption activity of nonstarch polysaccharides in the gastrointestinal tract. The main structural feature of both pectin and alginate is similar and consists of the uronic acid residues (Khotimchenko et al. 2001; Schols and Voragen 1996). They are not depolymerized by endogenous gastrointestinal enzymes and not absorbed during the passage through stomach and small intestine. Polysaccharides form an amorphous matrix providing water-holding and -binding capacities, passing through upper parts of gastrointestinal tract. The presence of free carboxyl groups in the alginate or pectate molecule provides the ion-exchange activity for binding metal ions according to so called “egg-box” model (Grant et al. 1973). This model states that negative charges of carboxyl groups in polysaccharide molecules form covalent bonds with two valence metal ions. These bonds are rarely broken and allow bound metal to be removed with polysaccharide mass. It is typical of pectins to have carboxyl groups esterified with methyl residues. They do not form bonds with metal ions, reducing their metal-binding capacity. The more the number of free carboxyl groups in the molecule, the more intensive ion-exchange capacities pectin has (Manunza et al. 1998). In the pectate sample used in our experiments, the amount of acid residue esterified with methyl ether was approximately 1.2%. This low percentage should result in a high metal-binding capacity.
The efficient removal of the lead ions may be related to high affinity of lead with pectin molecule (Kartel, Kupchik, and Veisov 1999) and alginate molecule (Jodra and Mijangos 2001). It was found in equilibrium model tests that as pectins and alginates possess highest affinity for lead ions and one of the lowest ones to calcium ions. So the ion-exchange process results in substituting calcium ions with the lead ones in polysaccharide molecules.
Contradictory results were found in experiments on estimation of effects of polysaccharide samples on lead concentrations in heart and liver. Metal content in these organs was approximately several fold higher after administration of polysaccharides. These findings can be explained by fast removal of lead from bones and kidneys, rapid increase of blood lead level, and consequent accumulation of the metal in well-perfused organs such as liver and heart. This phenomenon is sometimes called a “bound” effect (Gerhardsson et al. 1999). It may present a danger due to high lead toxicity, so fast lead elimination is recommended to be avoided if possible. The doses of any agent proposed for removal of the stored lead should be carefully calculated and not induce elevation of blood lead level more than 10 μg/dl, which is a minimal toxic lead concentration (Markowitz 2000). Therefore, the main goal in the therapy of plumbism should be prevention of lead absorption and accumulation. Pectate and alginate belong to a group of substances called dietary fibers, which are essential components of man’s diet and may be consumed for a long period of time without restrictions (Monro 2004). So, calcium salts of pectin and alginate may be used as the agents to prevent lead absorption without side effects.
In conclusion it should be noted that health effects of dietary fibers as well as these of other detoxifying drugs, including activated charcoal, are in great degree dependent on chemical structure and, hence, physicochemical properties (Babel and Kurniawan 2003; Demibras 2004; Gonzales et al. 1998). Therefore the results obtained in our study may not be observed in polysaccharides with different chemical structures. This also may be true for lignin and activated charcoal, although the preparations used in this study were commercial preparations approved and recommended for treatment of acute and chronic heavy metal poisoning.
Footnotes
Figure and Tables
This study was supported by grant no. 05-II-CM-05-006 from the Presidium of the Far East Branch of Russian Academy of Sciences and Presidium of the Siberian Branch of Russian Academy of Medical Sciences. The authors express special gratitude for the cooperation of “Vostokpharm” Co., Ltd. (Vladivostok, Russia) for performance of chemical characterization of polysaccharide samples.