The effects of dietary calcium and phosphorus on the retention and excretion of lead in rats

In vitro assessment of mineral blocks as a cost-effective measure to reduce oral bioavailability of lead (Pb) in livestock

Soil contamination in former mining districts is a persistent problem resulting from the historic lack of legal requirements as regards land restoration after mine closures. Much of this polluted land is currently being used worldwide for livestock and big game production, with the consequent health risks for the animals exposed and the subsequent threats to food safety. Soil remediation and restoration may be unfeasible or difficult to accomplish in the short term when pollution affects large territories and other alternatives must, therefore, be explored in order to reduce the probability of grazing animals being exposed to this contamination. In this paper, we study the use of mineral blocks (MBs) as a potential alternative by which to reduce the oral bioavailability of lead (Pb) in polluted soils by means of a simplified in vitro assay simulating gastrointestinal pH conditions. Experiments were carried out with twelve commercial MBs of different compositions in order to identify the most useful to be tested in further in vivo bioavailability studies. The results showed that one of them reduced the bioaccessibility of Pb from polluted soil by 88.2% and 75.9% under gastric and intestinal conditions, respectively, when compared with assays containing only polluted soil without MBs. The MB in question had the highest phosphorus content (7%) and one of the highest calcium contents (10%) of all those tested. Furthermore, negative correlations were detected between the content of calcium and phosphorus in the MBs and the percentage of bioaccessible Pb under gastric conditions, and between phosphorus and bioaccessible Pb under intestinal conditions. The use of MBs with a high phosphorus and calcium content should consequently be tested in vivo as a cost-effective (€ 0.6-1.5/sheep/month) tool by which to reduce the bioavailability of Pb for extensive grazing livestock reared in contaminated areas.

Dietary Lead and Phosphate Interactions Affect Oral Bioavailability of Soil Lead in the Mouse

Effects of dietary P level on the oral bioavailability of Pb present in soil were examined in a mouse model. Adult female C57BL/6 mice had free access to AIN-93G purified rodent diet amended with Pb as a soluble salt, Pb acetate, or in a soil matrix (NIST SRM 2710a). In these studies, the basal diet contained P at a nutritionally sufficient level (0.3% w/w) and the modified diets contained P at a lower (0.15%) or a higher (1.2%) level. For either dietary Pb source (Pb acetate or NIST SRM 2710a), low dietary P level markedly increased accumulation of Pb in bone, blood, and kidney. Tissue Pb levels in mice fed a high P in diet were not different from mice fed the basal P diet. Dietary P and Pb interacted to affect body weight change and feed efficiency in mice. The relative contribution of different Pb species in diet and feces was also affected by dietary P level. Differences in Pb species between diet and feces indicated that transformation of Pb species can occur during gastrointestinal tract transit. These interactions between Pb and P that alter Pb speciation may be important determinants of the bioavailability of Pb ingested in soil.

A pharmacokinetic model of lead absorption and calcium competitive dynamics

Lead is a naturally-occurring element. It has been known to man for a long time, and it is one of the longest established poisons. The current consensus is that no level of lead exposure should be deemed "safe". New evidence regarding the blood levels at which morbidities occur has prompted the CDC to reduce the screening guideline of 10 μg/dl to 2 μg/dl. Measurable cognitive decline (reduced IQ, academic deficits) have been found to occur at levels below 10 μg/dl, especially in children. Knowledge of lead pharmacology allows us to better understand its absorption and metabolization, mechanisms that produce its medical consequences. Based upon an original and very simplified compartmental model of Rabinowitz (1973) with only three major compartments (blood, bone and soft tissue), extensive biophysical models sprouted over the following two decades. However, none of these models have been specifically designed to use new knowledge of lead molecular dynamics to understand its deleterious effects on the brain. We build and analyze a compartmental model of lead pharmacokinetics, focused specifically on addressing neurotoxicity. We use traditional phase space methods, parameter sensitivity analysis and bifurcation theory to study the transitions in the system's behavior in response to various physiological parameters. We conclude that modeling the complex interaction of lead and calcium along their dynamic trajectory may successfully explain counter-intuitive effects on systemic function and neural behavior which could not be addressed by existing linear models. Our results encourage further efforts towards using nonlinear phenomenology in conjunction with empirically driven system parameters, to obtain a biophysical model able to provide clinical assessments and predictions.

Lead poisoning in United States-bound refugee children: Thailand-Burma border, 2009

BACKGROUND

Elevated blood lead levels lead to permanent neurocognitive sequelae in children. Resettled refugee children in the United States are considered at high risk for elevated blood lead levels, but the prevalence of and risk factors for elevated blood lead levels before resettlement have not been described.

METHODS

Blood samples from children aged 6 months to 14 years from refugee camps in Thailand were tested for lead and hemoglobin. Sixty-seven children with elevated blood lead levels (venous ≥10 µg/dL) or undetectable (capillary <3.3 µg/dL) blood lead levels participated in a case-control study.

RESULTS

Of 642 children, 33 (5.1%) had elevated blood lead levels. Children aged <2 years had the highest prevalence (14.5%). Among children aged <2 years included in a case-control study, elevated blood lead levels risk factors included hemoglobin <10 g/dL, exposure to car batteries, and taking traditional medicines.

CONCLUSIONS

The prevalence of elevated blood lead levels among tested US-bound Burmese refugee children was higher than the current US prevalence, and was especially high among children <2 years old. Refugee children may arrive in the United States with elevated blood lead levels. A population-specific understanding of preexisting lead exposures can enhance postarrival lead-poisoning prevention efforts, based on Centers for Disease Control and Prevention recommendations for resettled refugee children, and can lead to remediation efforts overseas.

Exposure to multiple metals from groundwater-a global crisis: geology, climate change, health effects, testing, and mitigation

This paper presents an overview of the global extent of naturally occurring toxic metals in groundwater. Adverse health effects attributed to the toxic metals most commonly found in groundwater are reviewed, as well as chemical, biochemical, and physiological interactions between these metals. Synergistic and antagonistic effects that have been reported between the toxic metals found in groundwater and the dietary trace elements are highlighted, and common behavioural, cultural, and dietary practices that are likely to significantly modify health risks due to use of metal-contaminated groundwater are reviewed. Methods for analytical testing of samples containing multiple metals are discussed, with special attention to analytical interferences between metals and reagents. An overview is presented of approaches to providing safe water when groundwater contains multiple metallic toxins.

Subchronic lead feeding study in male rats

This study was done to establish baseline information on the bioavailability of low levels of different species of lead by oral feeding in young rats and to compare this with lead-contaminated soils of similar dosage. These results can be used to help establish low-level risk assessments for lead exposure in children. Lead acetate was used in this study as a point of reference because it was considered to be 100% bioavailable. The required amounts of either lead acetate or lead nitrate were added to the control soil of 135 mg/kg lead to match the targeted test soil lead concentrations of 375, 750, 1500, and 3000 mg/kg lead. This lead-contaminated soil was mixed 5% (soil/diet) by weight with a semipurified lab chow diet, which resulted in final dietary lead concentrations of 6.75, 18.75, 37.5, 75, and 150 microg Pb/g diet. Results from this study indicated that (1) the dietary lead concentrations used did not result in any overt signs of lead toxicity (i.e., no significant effect on body weight gain, food consumption, or fecal output), (2) there were significant dose-dependent increases in fecal lead concentration and total fecal lead output, although there were no significant differences among study groups, (3) there was a time-dependent decrease in net whole-body lead uptake from a total group average of 65% at week 1 down to approximately 40% by week 5, and (4) there were no significant differences in terminal blood lead levels among study groups. Results from this study demonstrated a significant dose-dependent increase in tissue lead concentrations (mug Pb per g tissue weight) for bone, kidney, and liver for all study groups. There were no significant differences between the lead acetate and the test soil study groups at any lead dosages; however, there was a significantly increased lead incorporation into the bones from the lead nitrate study group. In summary, these results demonstrate that rats metabolize and handle lead of relatively small particle size from different soils and from different sources in a similar manner, although the use of lead acetate as the standard for 100% bioavailability might need to be reevaluated.

Assessment of Lead Ecotoxicity in Water using the Amphibian Larvae (Xenopus laevis) and Preliminary Study of its Immobilization in Meat and Bone Meal Combustion Residues

Lead (Pb) is a major chemical pollutant of the environment. It has been associated with human activities for the last 6000 years. Quite rightly, it remains a public health concern today. The present investigation evaluates the toxic potential of Pb in larvae of the toad Xenopus laevis after 12 days exposure in lab conditions. Acute toxicity, genotoxicity and Pb bioaccumulation were analyzed. The genotoxic effects were analyzed in the circulating blood from the levels of micronucleus induction according to the French standard micronucleus assay (AFNOR 2000 Association française de normalization. Norme NFT 90-325. Qualité de l'Eau. Evaluation de la génotoxicité au moyen de larves d'amphibien (Xenopus laevis, Pleurodeles waltl)). Lead bioaccumulation was analyzed in the liver of larvae at the end of exposure. Moreover, the toxic potential of lead, in aquatic media, was investigated in the presence of meat and bone meal combustion residues (MBMCR) known to be rich in phosphates and a potential immobiliser of lead. Previously, acute toxicity and genotoxicity of MBMCR alone were evaluated using Xenopus larvae. The results obtained in the present study demonstrated: (i) that lead is acutely toxic and genotoxic to amphibian larvae from 1 mg Pb/l and its bioaccumulation is significant in the liver of larvae from the lowest concentration of exposure (1 microg Pb/l), (ii) MBMCR were not acutely toxic nor genotoxic in Xenopus larvae, (iii) lead in presence of MBMCR induced inhibition or reduction of the toxic and genotoxic potential of lead in water at concentrations that do not exceed the capacity of MBMCR of Pb-binding (iv) Pb accumulation in larvae exposed to lead with MBMCR in water was lower than Pb-accumulation in larvae exposed to lead alone except at the concentration of 0.01 mg Pb/l suggesting complex mechanisms of MBMCR interaction in organisms. The results confirm the high toxicity and genotoxicity of lead in the aquatic compartment and suggest the potential utility of MBMCR for use in remediation.

Elevated blood lead resulting from maxillofacial gunshot injuries with lead ingestion

PURPOSE

The purpose of this study was to identify the contribution of ingested lead particles to elevated blood lead concentrations in victims of gunshot injury to the maxillofacial region.

PATIENTS AND METHODS

As part of a larger study of the effects of retained lead bullets on blood lead, a retrospective review of study findings was completed on 5 of 8 patients who sustained injuries to the maxillofacial region. These 5 patients were recruited into the larger study within 11 days of injury and showed a penetration path for the projectile that engaged the upper aerodigestive tract. All subjects were recruited from patients presenting for care of their gunshot injuries to a large inner-city trauma center with a retained bullet resulting from a gunshot injury. An initial blood lead level was measured for all recruited patients and repeated 1 to 17 weeks later. Medical history was taken along with a screening and risk factor questionnaire to determine other potential or actual sources (occupational/recreational) of lead exposure. (109)Cd K-shell x-ray fluorescence determinations of bone lead were completed to determine past lead exposure not revealed by medical history and risk factor questionnaire. Radiographs taken of the abdomen and chest, required as a part of the patient's hospital care, were retrospectively reviewed for signs of metallic fragments along the aerodigestive tract.

RESULTS

All 5 patients retained multiple lead pellets or fragments at the site of injury, sustained fractures of the facial bones, and showed increases in blood lead. Three of the 5 study subjects who sustained maxillofacial gunshot injuries involving the mouth, nose, or throat region showed metallic densities along the gastrointestinal tract indicative of ingested bullet fragments. Each patient with ingested bullet fragments showed rapid elevation of blood lead exceeding 25 microg/dL and sustained increases well beyond the time when all ingested fragments were eliminated. A 3-year follow-up on these 3 patients showed significantly sustained elevation of blood lead but less than that observed during the initial 6 months after injury. None of the 5 study subjects showed any evidence of metallic foreign bodies within the tracheobronchial regions indicative of aspiration.

CONCLUSION

Ingestion of lead fragments can result from gunshot injuries to the maxillofacial region and may substantially contribute to a rapid increase in blood lead level. Prompt diagnosis and elimination of ingested lead fragments are essential steps necessary to prevent lead being absorbed from the gastrointestinal tract. Increased blood lead in victims after gunshot injuries must be fully evaluated for all potential sources, including recent environmental exposure, absorption of lead from any remaining bullets in body tissues, and the possibility of mobilization of lead from long-term body stores such as bone.

Elements in environmental and occupational medicine

Occupational and environmental medicine traditionally dealt with elements, particularly with heavy metals. The interest was justified by the wide exposure in the workplace and in the general environment and by the evidence of their specific biological and toxicological effects. During the last 2 decades of 20th century the availability of indicators of exposure or of internal dose has substantially increased thanks to improvement in AAS-ETAAS techniques and to the entrance of ICP-MS into the field of biological monitoring. There are now more and more demands for controlling pre-analytical and analytical factors, for analysing biological matrices in addition to blood and urine and for setting up methods for elements not yet extensively studied in respect to their possible biological or toxicological role. Finally, deeper knowledge has to be reached in order to evaluate the significance of elements and, possibly, of their species in biological fluids at current doses and in order to face their effects, especially those in the first portion of the dose-response curve, which is going to be the main field of interest of occupational and environmental toxicology for the next few years.

The Effects of Retained Lead Bullets on Body Lead Burden

BACKGROUND

Numerous case reports have demonstrated that lead poisoning with potentially fatal consequences can result from retained lead projectiles after firearm injuries. To assess the impact of retained projectiles on subsequent lead exposure in the population, one cannot rely on self-selected cases presenting with symptoms of lead intoxication. This preliminary study seeks to identify increased lead burden and identify risk factors of elevated blood lead levels for individuals with retained lead bullets.

METHODS

Forty-eight patients were originally recruited from gunshot victims presenting for care at the King/Drew Medical Center in Los Angeles, California. An initial blood level was measured for all recruited patients and repeated for the 28 participants available for follow-up, 1 week to 8 months later. Medical history, including a history of prior firearm injuries and other retained projectiles, was taken, along with a screening and risk factor questionnaire to determine other sources of lead (occupational/recreational) to which the patient might have been, or is at present, exposed. The participants also had K-shell x-ray fluorescence determinations of bone lead in the tibia and calcaneus in order to determine past lead exposures not revealed by medical history and risk factor questionnaire. Multivariate models of blood level were made using risk factor and bone lead concentration data.

RESULTS

We demonstrated that blood lead tends to increase with time after injury in patients with projectile retention, and that the increase in significant part depended on the presence of a bone fracture caused by the gunshot.

CONCLUSION

We encountered evidence suggesting that the amount of blood lead increase in time after injury is also dependent on the tibia lead concentration. There were too few cases in the study to fully test the effects of bullet location, or the interaction of bullet location with bone fracture or bullet fragmentation.

Recommending calcium to reduce lead toxicity in children: a critical review

Assertions that adequate or supplemental calcium intake can reduce lead absorption in children are based on liberal extrapolation from animal studies, experiments with human adults, and cross-sectional studies of children that have a variety of methodologic weaknesses. Without stronger supporting evidence, statements that diet can ameliorate the deleterious effects of environmental lead could provide a false sense of efficacy and divert efforts from lead abatement and from behavioral modifications that might have more impact.

Blood lead levels and calcium intake in Mexico City children under five years of age

OBJECTIVE

The relationship between daily calcium intake and blood lead levels was evaluated among children under five years of age living in Mexico City.

METHODS

A random sample of 200 children under five years of age, resident in two neighborhoods of Mexico City was selected: Xalostoc, an industrial neighborhood, and Tlalpan, a residential neighborhood (100 from each area). The mothers of these children filled out a questionnaire on predictors of blood lead levels including daily calcium intake. Lead levels were determined from the venous blood samples. Calcium intake was assessed using a short Food Frequency Questionnaire including 11 food items that accounted for 95% of calcium intake in Mexico.

RESULTS

The average blood lead level was 9.93 microg dl(-1) (range 1-31 microg dl(-1)). An inverse relationship was observed between blood lead levels and daily calcium intake. This relationship was statistically significant among children aged 13 months-5 years.

CONCLUSION

The results suggest that calcium provided a protective effect against lead accumulation in the body among children. Further studies should be undertaken to evaluate this hypothesis through experimental design.

[Physiopathology of inorganic lead poisoning]

This paper gives an overview of the hypotheses concerning the mechanisms of inorganic lead toxicity on cells and tissues, with emphasis on the effect of low-concentration lead. Inhibition of heme synthesis is responsible not only for lead-induced anaemia, but also for accumulation of delta-aminolaevulinic acid (ALA) and for lowering the concentration of cytochromes contained in the mitochondrial respiratory chain. Auto-oxidation of ALA is thought to result in the formation of free radicals. On the other hand, lead replaces ionic calcium in its role as second cell messenger. This mechanism would explain the abnormalities observed in synaptic transmission, arteriolar vasoreactivity and functioning of such cells as osteoclasts and osteoblasts. Nuclear toxicity, with abnormal expression of DNA genes and inhibition of certain enzymes such as membrane Na+/K+ ATPase, are also considered. The mechanisms of tissue toxicity are discussed.

The effects of dietary calcium on lead absorption, distribution, and elimination kinetics in rats

A pharmacokinetic analysis of lead absorption, distribution, and elimination was conducted in rats maintained on calcium-deficient, control, and calcium-supplemented diets. Dietary calcium affected lead disposition in a number of ways. Systemic lead clearance after a 10-mg/kg intracardiac lead dose was approximately 25% lower than control in rats administered dietary calcium supplements. Intestinal absorption of 10 mg/kg po lead doses was not affected by the calcium supplements. In rats maintained on a calcium-deficient diet, systemic lead clearance was estimated to be 40% less than control. The apparent volume of lead distribution was increased. The apparent systemic availability of 1-, 10-, and 100-mg/kg oral lead doses was three- to fourfold greater than control in calcium-deficient rats. The percentage absorption was dose-dependent in control and calcium-deficient rats. The observed changes in lead absorption and systemic clearance associated with the calcium-deficient diet represent synergistic effects that could elevate blood lead accumulation and thus potentially influence susceptibility to lead toxicity.

Lead toxicity in the chick as affected by excess copper and zinc and by Eimeria acervulina infection

Several experiments were performed with young chicks to evaluate lead (Pb) toxicity and its effect upon copper (Cu) and zinc (Zn) toxicosis in the presence or absence of Eimeria acervulina infection. Toxic levels of Pb (3300 mg/kg) and Cu (500 mg/kg) or Zn (2000 and 4000 mg/kg) were added to completely adequate corn-soybean meal diets, while duodenal coccidiosis was produced by multiple crop inoculations of 4 X 10(5) sporulated E. acervulina oocysts. Both Pb and Cu depressed gain and feed efficiency while concomitant coccidial infection reduced these parameters further. Moreover, E. acervulina increased the concentration of liver Cu and kidney Pb. Although Pb supplementation slightly decreased the accumulation of liver Cu, additional Cu tended to increase the deposition of Pb in the kidney in both infected and uninfected birds. Similarly, chick performance was significantly reduced by excess dietary Pb or Zn, although coccidiosis slightly ameliorated the growth depression caused by toxic levels (4000 mg/kg) of Zn. Although 4000 ppm Zn and coccidial infection reduced the deposition of Pb in the kidney, this interaction was not evident when 2000 mg/kg Zn was fed to infected chicks. It is evident that Pb toxicosis in the chick is affected little by excess dietary levels of either Cu or Zn.

Differential retention of 212Pb ions and insoluble particles in nasal mucosa of the rat

The time course of retention of 212Pb ions in ciliated nasal epithelium and of tagged insoluble particles, which served both as a deposition vector and marker for mucus, was measured in 13 rats by counting the head externally at 2 min intervals up to 100 min after deposition. On average, 70-75% of insoluble particles introduced onto ciliated epithelium in 3 microliters of distilled water were cleared to the gut with a half-time of approximately 15 min (range 6-35 min). A smaller fraction of lead ions (averaging about 60%) introduced in the same water sample was cleared to the gut with a half-time in each rat similar to that of particle clearance. Rapid uptake of about 8% of deposited 212Pb into blood was also observed. A compartment model consistent with the observed nasal retention and appearance of 212Pb in blood showed that, on average, 8% of deposited lead ions were transferred to the blood with a half-time of 15 min. For about 35% of the deposited lead ions and 25% of the particles, no clearance was detected up to 60-100 min after deposition. It is probable that a fraction of the lead ions are retained by epithelial tissue.

Regional alterations of brain catecholamines by lead ingestion in adult rats. Influence of dietary calcium

The alterations in steady-state dopamine (DA) and norepinephrine (NE) content of hypothalamus-median eminence (HME) and striatum (STR) were measured in adult female rats fed normal calcium (1.2%) or low calcium (0.005%) diets for 4 weeks and exposed to lead via drinking water containing lead acetate (0.032, 0.32, and 3.2 mg Pb/ml) for the last 3 weeks of a 4-week diet period. Control lead-free groups of both dietary regimens received equimolar acetate as sodium acetate. The eight groups (six rats/group) were divided equally between the two diet regimens. Three weeks treatment with lead significantly reduced DA and NE in HME but DA only in STR (0.32 and 3.2 mg Pb/ml) of both dietary groups. Low dietary calcium alone reduced DA and NE in HME. In contrast with the HME low calcium diet alone had no significant effect on DA and NE in STR. No additive effect of low calcium diet and lead ingestion in catecholamine reduction was found in the brain parts studied.

Enhanced teratogenicity of orally administered lead in hamsters fed diets deficient in calcium or iron

A preliminary investigation was carried out to determine if dietary deficiencies in calcium or iron enhance the embryotoxic and teratogenic effects of orally administered lead in hamsters. Females of experimental groups were given drinking water containing 0.05% or 0.1% lead acetate and a calcium or iron deficient diet for several weeks prior to and/or during pregnancy. The incidence of embryonic/fetal mortality and of abnormal fetuses was markedly increased in litters delivered from these animals near term (15th gestational day) compared with litters from control animals similarly exposed to leaded drinking water but fed complete diets.

Will consumption or oral contraceptives enhance the gastrointestinal absorption of lead

Consumption of a specific oral contraceptive (OC) preparation resulted in the enhanced gastrointestinal (GI) tract absorption of calcium. Since calcium and lead may compete for the same binding site in the GI mucosa and since lactose enhances the GI uptake of a variety of minerals such as calcium and lead, it is speculated that other agents such as certain OC preparations which facilitate the GI absorption of calcium may also enhance the GI uptake of lead.

Lattice parameters and cation distribution of solid solutions of calcium and lead hydroxyapatite

Solid solutions of calcium hydroxyapatite (CaOHA) and lead hydroxyapatite (PbOHA) of the formula Ca10-x Pbx (PO4)6 (OH)2 were prepared by coprecipitation followed by heating at 800 degrees C in a steam of CO2-free water vapor of 1 atm. The samples were apatitic in the range 0 less than x less than 6 and contained lead phosphates as a second phase at higher Pb/Ca ratios. Lattice parameters and cation distribution of the apatitic samples were determined by X-ray diffraction. The lattice parameters varied linearly with x in the range considered, whereas all Pb2+ were located in the six-fold position for cations. There was a miscibility gap in the apatite series of solid solutions in the range 1 less than x less than 4, whereas apatites in the range 6 less than x less than 10 were not stable under the conditions of preparation. It is concluded that apatites in the range 4 less than x less than 6 represent a minimum in the free energy of solid solutions between CaOHA and PbOHA.

Lead toxicity and nutritional deficiencies

Under appropriate conditions, deficiencies of certain minerals and vitamins as well as high intakes of dietary fat increase the toxicity of a given dose of lead in experimental animals. The severity of lead poisoning can also be increased by the consumption of either deficient or excessive levels of protein. Mineral deficiencies appear to have some of the most profound effects on lead toxicity, since the consequences of plumbism can be exaggerated by feeding diets low in calcium, phosphorus, iron, zinc, and in some cases, copper. Evidence for an antagonism between lead and nutritional levels of selenium is inconclusive. Vitamin E deficiency and lead poisoning interact to produce an anemia in rats that is more severe than that caused by either treatment alone. Lead apparently exerts a pro-oxidant stress on the red cell, thereby causing its accelerated destruction. One of the biochemical mechanisms of lead poisoning may be the disruption of normal membrane architecture, thereby leading to peroxidative damage. Epidemiological surveys have suggested a negative correlation between the poor nutritional status of children with regard to calcium and the concentration of lead in blood. Other examples of potential interactions of mineral status and lead poisoning in humans include the hypothesized hazards of soft water to public health in areas with lead plumbing and the possible role of mineral deficiencies in the etiology of pica. Experimental studies have shown that in some situations combined nutritional deficiencies can have an additive effect in potentiating lead toxicity.

The influence of high dietary calcium and phosphate on lead uptake and release

The effects of calcium and phosphate supplements on the retention of dietary lead and the loss of lead from the body were studied in young rats. There were three experiments in which rats were given a diet containing 200 or 400 micrograms of lead/g for 3 or 6 weeks. The diet contained adequate calcium and phosphate. Calcium and phosphate supplements were given alone or together. Lead uptake after a period of lead feeding was measured by analysis of the whole gut-free carcass. Lead loss was measured by a similar analysis after the rats had received diets containing lead and then diets free of lead. The uptake of lead from the diet was reduced by about half when either dietary calcium or phosphate or both was doubled. The rate of release of body lead was decreased by calcium supplementation.