Environmental lead exposure and the kidney

The Association between Mercury and Lead Exposure and Liver and Kidney Function in Pregnant Surinamese Women Enrolled in the Caribbean Consortium for Research in Environmental and Occupational Health (CCREOH) Environmental Epidemiologic Cohort Study

Exposure to mercury (Hg) and lead (Pb) may have an effect on pregnant women. We assessed the effect of exposure to mercury and lead on liver and kidney functions in a subcohort of pregnant women who participated in the Caribbean Consortium for Research in Environmental and Occupational Health (CCREOH)—Meki Tamara, study. From 400 women aged 16−46 living in rural, urban, and interior regions of Suriname, we measured blood mercury and blood lead levels. Creatinine, urea, and cystatin C were measured to assess kidney function, and aspartate amino transferase (AST), alanine amino transferase (ALT), and gamma-glutamyl transferase (GGT) were measured to assess liver function. Education, region, and ethnicity showed significant differences for both blood mercury and lead levels, which all had p-values < 0.001. Creatinine and urea were elevated with higher mercury blood levels. Our findings also suggest a relationship between high mercury blood levels and potential harmful effects on liver and kidney function.

Genetically determined blood lead is associated with reduced renal function amongst individuals with type 2 diabetes mellitus: insight from Mendelian Randomisation

Some observational studies indicate a link between blood lead and kidney function although results remain controversial. In this study, Mendelian randomisation (MR) analysis was applied to obtain unconfounded estimates of the casual association of genetically determined blood lead with estimated glomerular filtration rate (eGFR) and the risk of chronic kidney disease (CKD). Data from the largest genome-wide association studies (GWAS) on blood lead, eGFR and CKD, from predominantly ethnically European populations, were analysed in total, as well as separately in individuals with or without type 2 diabetes mellitus. Inverse variance weighted (IVW) method, weighted median (WM)-based method, MR-Egger, MR-Pleiotropy RESidual Sum and Outlier (PRESSO) as well as the leave-one-out method were applied. In a general population, lifetime blood lead levels had no significant effect on risk of CKD (IVW: p = 0.652) and eGFR (IVW: p = 0.668). After grouping by type 2 diabetes status (no diabetes vs. diabetes), genetically higher levels of blood lead had a significant negative impact among subjects with type 2 diabetes (IVW = Beta: -0.03416, p = 0.0132) but not in subjects without (IVW: p = 0.823), with low likelihood of heterogeneity for any estimates (IVW p > 0.158). MR-PRESSO did not highlight any outliers. Pleiotropy test, with very negligible intercept and insignificant p-value, indicated a low likelihood of pleiotropy for all estimations. The leave-one-out method demonstrated that links were not driven by a single SNP. Our results show, for the first time, that among subjects with type 2 diabetes, higher blood lead levels are potentially related to less favourable renal function. Further studies are needed to confirm our results. KEY MESSAGES: What is already known about this subject? Chronic kidney disease is associated with unfavourable lifestyle behaviours and conditions such as type 2 diabetes. Observational studies have reported an association between blood lead and reduced estimated glomerular filtration rate, but the relationship between lead exposure and renal function remains controversial. What is the key question? Using Mendelian randomisation with data from 5433 individuals from the UK and Australian populations, does genetically determined blood lead have a potentially causal effect on estimated glomerular filtration rate and the risk of chronic kidney disease? What are the new findings? Blood lead levels have a potentially causal effect on reduced renal function in individuals with type 2 diabetes. In subjects without diabetes, no such causal relationship was identified. How might this impact on clinical practice in the foreseeable future? This highlights the risk of elevated blood lead, for example, due to environmental exposure, amongst those with type 2 diabetes, which may predispose them to impaired renal function.

Chemical exposure in garage workers and related health risks on the biochemical levels: A comparative study in Harar town, eastern Ethiopia

Objectives

Occupational exposure to chemicals causes a wide range of biological effects depending on the level and duration of exposure. The current study is intended to determine the differences in biochemical levels among garage workers compared with occupationally nonexposed participants in Harar town, eastern Ethiopia.

Methods

A comparative cross-sectional study was conducted in Harar town, eastern Ethiopia. Thirty (30) garage workers were selected and compared with 30 age- and sex-matched control group of teachers and students. Demographic and occupational data were collected using a structured questionnaire by trained data collector. Biochemical levels were measured by automated clinical chemistry analyzer (Autolab 18, Boehringer-Mannheim Diagnostics, the United States). Data were analyzed using STATA Version 13.

Results

All of the included garage workers were male. A statistically significant increase were found in alanine aminotransferase (35.60 ± 7.93 vs 19.17 ± 0.91 U/L; P value = 0.0440), aspartate aminotransferase (47.23 ± 4.89 vs 27.03 ± 1.13 U/L; P value = 0.0002), total protein (85.83 ± 1.16 vs 76.40 ± 0.86 g/l; P value < 0.0001), uric acid (7.34 ± 0.29 vs 5.19 ± 0.21 mg/dl; P value < 0.0001), glucose (85.13 ± 3.92 vs 75.60 ± 2.40 mg/dl; P value = 0.0425); total cholesterol (199.40 ± 13.11 vs 140.37 ± 3.81 mg/dl; P value = 0.0001) and triglyceride (143.40 ± 5.79 vs 110.60 ± 8.98 mg/dl; P value = 0.0033) in garage workers compared with control group. On the contrary, a statistically significant decrease were found in albumin (39.37 ± 1.78 vs 46.37 ± 0.56 g/l; P value = 0.0004) and urea (21.63 ± 1.04 vs 27.60 ± 1.69 mg/dl; P value = 0.0039) among garage workers compared with the control group.

Conclusion

Our finding indicates that working in the garage changes most of the biochemical levels. Therefore, appropriate and effective safety measures need to be implemented to prevent possible chemical exposure during routine work.

Glycine supplementation mitigates lead-induced renal injury in mice

Purpose

Lead (Pb) is an environmental pollutant responsible for various organ damages including renal injury. It seems that OS and associated events are crucial mechanisms of lead-induced renal dysfunction. The current study aimed to explore the potential protective effects of glycine against renal injury caused by lead in mice.

Materials and methods

Mature male mice (n=32) were allocated into four groups. The following treatment regimens were the control (vehicle-treated); Pb-acetate (20 mg/kg/day, gavage); Pb-acetate + glycine (500 mg/kg/day, IP); and Pb-acetate + glycine (1,000 mg/kg/day, IP). Pb-acetate + glycine was administered for 14 consecutive days, Pb-acetate was given first and then glycine at least 6 hours later. On day 15, the subjects were anesthetized, and samples were collected. Serum biomarkers such as BUN and serum creatinine were monitored along with formation of reactive oxygen species, lipid peroxidation, kidney GSH level, and histopathological changes.

Results

Based on the results, BUN and serum creatinine levels significantly increased following exposure to lead. Glycine supplementation (500 and 1,000 mg/kg, IP) decreased BUN and creatinine serum levels (P<0.001). Biomarkers of OS were also reduced in renal tissue following glycine therapy in Pb-exposed mice (P<0.001). Histopathological changes were observed in mice treated with lead as tubular dilation, protein cast, vacuolization, and inflammation. In this regard, glycine inhibited histopathological alterations in kidney caused by lead exposure.

Conclusion

It was found that glycine treatment significantly mitigated Pb-induced renal injury most likely through alleviating OS and the associated deleterious outcomes on the kidney tissue.

Role of essential trace minerals on the absorption of heavy metals with special reference to lead

Heavy metals are important toxicants known to exert adverse effects in humans and animals, given sufficient exposure and accumulation in the body. This has a great concern both at personal and public health risk. Heavy metals are also known to interact with the essential trace minerals at the level of absorption and also during the metabolism. The adverse effects of the absorbed and accumulated heavy metals include neurological, reproductive, renal and hematological systems. Children are more sensitive than adults to the effects of lead. Efforts are made to understand the mechanism of the interactions of heavy metals with essential trace minerals at the level of absorption. With available sensitive and specific methodologies like Anodic Stripping Voltammetry for the evaluation of the levels of toxic heavy metals such as lead, cadmium, mercury etc., better understanding of heavy metal absorption is made possible.Due to the poor nutritional standards, risk of heavy metal exposure is still a major concern in developing countries. Studies carried out by the author have provided evidence towards the understanding of the prevailing mechanisms of metal-metal interaction at the intestinal level. During growth and development the demand for the essential minerals being at higher level, differentiation of various essential metals and heavy metals pose an inherent problem due to certain common properties shared by them. With this approach to the problem of heavy metal toxicity, it is preventable not only with environmental intervention but also by the nutritional management.

Lead exposure study among workers in lead acid battery repair units of transport service enterprises, Addis Ababa, Ethiopia: a cross-sectional study

BACKGROUND

Lead exposure is common in automobile battery manufacture and repair, radiator repair, secondary smelters and welding units. Urinary Aminolevulinic acid has validity as a surrogate measure of blood lead level among workers occupationally exposed to lead. This study had therefore assessed the magnitude of lead exposure in battery repair workers of three transport service enterprises.

METHODS

To this effect, a cross-sectional study was carried out on lead exposure among storage battery repair workers between November 2004 and May 2005 from Anbasa, Comet and Walia transport service enterprises, Addis Ababa, Ethiopia. Subjective information from the workers was obtained by making use of structured questionnaire. Other information was obtained from walkthrough evaluation of the repair units. Aminolevulinic acid levels in urine were used as an index of the exposure. This was coupled to measurements of other relevant parameters in blood and urine collected from adult subjects working in the repair units as well as age matched control subjects that were not occupationally exposed to lead. Aminolevulinic acid was determined by spectrophotometry, while creatinine clearance, serum creatinine, urea and uric acid levels were determined using AMS Autolab analyzer.

RESULTS

Urinary aminolevulinic acid levels were found to be significantly higher in exposed group (16 mug/ml +/- 2.0) compared to the non-exposed ones (7 mug/ml +/- 1.0) (p < 0.001). Alcohol taking exposed subjects exhibited a significant increase in urinary aminolevulinic acid levels than non-alcohol taking ones (p < 0.05). Moreover, urinary aminolevulinic acid levels of exposed subjects increased with age (p < 0.001) as well as duration of employment (p < 0.001). Whereas serum uric acid levels of exposed subjects was significantly higher than non-exposed ones (p < 0.05), no statistically significant difference had been found in renal indices and other measured parameters between exposed and non-exposed subjects. From the questionnaire responses and walkthrough observations, it was also known that all the repair units did not implement effective preventive and control measures for workplace lead exposure.

CONCLUSION

Taken together, these findings indicated that workers in lead acid battery repair units of the transport service enterprises are not protected from possibly high lead exposure. Thus, strict enforcement of appropriate and cost effective preventive and control measures is required by all the enterprises.

Association of tibia lead and blood lead with end-stage renal disease: a pilot study of African-Americans

The association between body lead burden and kidney disease remains controversial. Fifty-five African-American end-stage renal disease (ESRD) cases and 53 age- and sex-matched African-American controls without known renal disease were recruited from Tulane University-affiliated dialysis clinics and out-patient clinics, respectively. Blood lead was measured via atomic absorption spectrophotometry and tibia lead (a measure of body lead) was measured via (109)Cd-based K shell X-ray fluorescence. Median blood lead levels were significantly higher among ESRD cases (6 microg/dL) compared to their control counterparts (3 microg/dL; P<0.001). Although no participants had overt lead poisoning (blood lead > or = 25 microg/dL), seven cases but no controls had blood lead levels above 10 microg/dL (P=0.006). The median tibia lead level was 17 micrograms of lead per gram of bone mineral (microg/g) and 13 microg/g among ESRD cases and their control counterparts, respectively (P=0.134). Four ESRD cases (7%), but no controls, had a tibia lead level above 40 microg/g (P=0.115) while a similar proportion of cases and controls had tibia lead between 20 and 39 microg/g (33% and 32%, respectively; P=0.726). After adjustment for potential confounders, the odds ratios of ESRD associated with a tibia lead > or = 20 microg/g and each four-fold higher tibia lead (e.g., 5-20 microg/g) were 1.55 (95% CI: 0.55, 4.41) and 1.88 (95% CI: 0.53, 6.68), respectively. These findings support the need for prospective cohort studies of body lead burden and renal disease progression.

Micronuclei in peripheral blood lymphocytes of workers exposed to lead

Lead plays an important role in many industrial processes. Although highly useful to man, lead has various types of toxic effects. There is constantly growing evidence of a relationship between the induction of chromosome breaks and an increased risk of onset of cancer. However, available data about the possible genotoxic and carcinogenic action of lead are conflicting. In this report we present the results of studies on lead concentrations in blood and the respective micronucleus frequencies in peripheral blood lymphocytes from workers employed in the recycling of automotive batteries in the surroundings of Porto Alegre, Brazil. We observed that in the occupationally exposed group, both lead concentration in peripheral blood and micronucleus frequency in lymphocytes were significantly higher compared to control (Z=6.35, P<0.0001 and Z=4.47, P<0.0001). The nuclear division index (NDI) values were significantly higher in the control group than in the exposed group (Z=2.13, P=0.0330), indicating a possible effect of Pb on nuclear proliferation. We also detected a negative correlation between micronuclei and progression of nuclear division (tau=-0.312, P=0.0129). There were no changes in micronucleus frequency between smoking and non-smoking workers exposed to lead (Z=0.03, P=0.9790). The only difference found between the groups of smokers and non-smokers was with respect to NDI, whose values were significantly higher among non-smokers (Z=1.98, P=0.0481).

Therapeutic efficacy of lipoic acid in combination with dimercaptosuccinic acid against lead-induced renal tubular defects and on isolated brush-border enzyme activities

The combined therapeutic potentials of lipoic acid and dimercaptosuccinic acid were compared against their sole administrations in restoring the altered lead sensitive indices in urine and isolated renal brush-border preparations. Toxicity was induced in male albino rats (Wistar strain) by administering lead acetate (0.2%) in drinking water for 5 weeks, followed by therapy comprising lipoic acid (25 mg/kg body weight) and dimercaptosuccinic acid (20 mg/kg body weight) solely as well as combined during the 6th week. Changes in kidney weights encountered upon lead administration improved after therapy with lipoic acid and dimercaptosuccinic acid. Renal integrity was assessed by measuring the activities of alkaline phosphatase, acid phosphatase, lactate dehydrogenase, leucine aminopeptidase, N-acetyl-beta-D-glucosaminidase, gamma-glutamyl transferase and beta-glucuronidase in urine along with some urinary constituents (urea, uric acid, creatinine, protein and phosphorous). The effects of lead were also studied on isolated brush-border enzymes (alkaline phosphatase, acid phosphatase, gamma-glutamyl transferase and beta-glucuronidase) that showed a decline upon its administration. Increased activities of urinary enzymes were accompanied by increase in the urinary constituents. Increase in renal lead content was paralleled by a drastic fall in the renal delta-aminolevulinic acid dehydratase and a rise in urinary lead levels. Relative to the administration of lead, the combined therapy showed betterment on the renal integrity with respect to the functional parameters assessed, thereby indicating its efficacy over the monotherapies.

Blood lead and chronic kidney disease in the general United States population: results from NHANES III

BACKGROUND

High lead exposure is associated with hypertension and renal dysfunction but the effect of low-level environmental exposure is not as well studied.

METHODS

We examined the association between blood lead and renal function among a representative sample of the civilian noninstitutionalized United States population with and without hypertension, age 20 years old or older, participating in the Third National Health and Nutrition Examination Survey (NHANES III) (N=15211). Elevated serum creatinine was defined as >or=99th percentile of each race-sex specific distribution for healthy young adults and chronic kidney disease (CKD) as a glomerular filtration rate (GFR) <60 mL/min estimated using the Modification of Diet in Renal Disease (MDRD) formula.

RESULTS

Among persons with and without hypertension, mean blood lead was 4.21 and 3.30 ug/dL, respectively, the prevalence of elevated serum creatinine was 11.5% and 1.8%, respectively, and CKD was 10.0% and 1.1%, respectively. Among persons with hypertension, a graded association was present between higher quartile of blood lead and a higher odds ratio of both an elevated serum creatinine and CKD. Comparing the highest to lowest quartile of blood lead, the multivariate adjusted odds ratio (95% CI) of an elevated serum creatinine and CKD were 2.41 (1.46, 3.97) and 2.60 (1.52, 4.45), respectively. The analogous adjusted odds ratios (95% CI) among normotensives were 1.09 (0.53, 2.22) and 1.09 (0.41, 2.89), respectively. Associations were consistent when modeling lead as a continuous variable and in all subgroups except smokers.

CONCLUSION

In the United States population with hypertension, exposure to lead, even at low levels, is associated with CKD. Reduction of lead exposure may reduce the burden of CKD in the community.

Health risk for children from lead and cadmium near a non-ferrous smelter in Bulgaria

In an interdisciplinary approach the exposure to lead and cadmium of the population living in the vicinity of a Bulgarian non-ferrous metallurgical plant was studied to determine the routes of exposure. Two exposed villages situated 4 and 6 km SW and W, respectively,--in the plume of the plant's emissions--and a village for comparison situated 14 km SE of the plant were selected for the study. The blood of children aged 3-13 years from the exposed villages (n = 111) and the village for comparison (n = 18) was analyzed for lead (PbB) and cadmium (CdB) as well as for free erythrocyte protoporphyrin (FEP) and haematological parameters. A personal questionnaire concerning nutrition habits and life-style was filled in by interviewers of the children's parents. The cadmium levels in blood were within the variation range stated for Bulgaria. The exposed children had a mean CdB of 0.38 +/- 0.18 microgram/l (range 0.10-0.90 microgram/l) and the comparison group 0.31 +/- 0.35 microgram/l (0.06-1.42 micrograms/l). The mean PbB value measured in the exposed children was 240 +/- 96 micrograms/l (77-631 micrograms/l), while the mean value of PbB for the reference group was 149 +/- 57 micrograms/l (63-285 micrograms/l). Individual PbB levels > 150 and > 200 micrograms/l were found in 85% and 62%, respectively, of the exposed children and FEP > 80 micrograms/dl erythrocytes was detected in 21%. There was a concentration-response and a concentration-effect relationship (r = 0.51, D > 0.001) between PbB and FEP. According to the questionnaire only 10.3% of the interviewed families in the two exposed villages buy all food from the market, the others produce a significant part of their food themselves. The PbB levels of children who consume certain foods of local production (cabbage, cereals, poultry, and beef) were significantly higher compared to the PbB values of children whose families purchase these foods from the market. No significant relationship between lead in children's blood and the use of tin and ceramic utensils, drinking and irrigation water, hygiene habits, family tobacco smoking habits, playgrounds and traffic intensity were revealed. There was a significantly higher incidence of prematurely born babies in the exposed population. The proven relationship between lead intake via the food chain and existing significant health risks is the basis for risk communication. Measures aimed at healthier nutrition and life-style intend to contribute to decreasing the risk of the population living in the smelter region.

Lead chelation therapy and urate excretion in patients with chronic renal diseases and gout

BACKGROUND

It is known that chronic renal insufficiency (CRI) patients with gout may have subtle lead poisoning. In addition, gout episodes frequently aggravate progressive renal insufficiency because of the use of nephrotoxic drugs and urate deposition. Our study was arranged to evaluate the causal effect of environmental lead exposure on urate excretion in CRI patients.

METHODS

A cross-section study and a randomized, controlled trial were performed. Initially, 101 patients with CRI and without a history of previous lead exposure received ethylenediaminetetraacetic acid mobilization tests to assess body lead stores (BLS). Then, a clinical trial was performed; 30 CRI patients with gout and high-normal BLS and the changes of urate excretion in these patients were compared before and after lead chelating therapy. The treated group received four-week chelating therapy, and the control group received a placebo therapy.

RESULTS

The BLS of patients with CRI and gout was higher than that of patients with CRI only, and none had subtle lead poisoning. The BLS, not the blood lead level (BLL), significantly correlated to indices of urate excretion in all CRI patients after related factors were adjusted. In addition, after lead chelating therapy, urate clearance markedly improved after a reduction of the BLS of patients with CRI and gout (study group 67.9 +/- 80.0% vs. control group 1.2 +/- 34.0%, P = 0.0056).

CONCLUSION

Our findings suggest that the chronic low-level environmental lead exposure may interfere with urate excretion of CRI patients. Importantly, the inhibition of urate excretion can be markedly improved by lead chelating therapies. These data shed light on additional treatment of CRI patients with gout; however, more studies are needed to confirm our findings.

Increase by NO synthase inhibitor of lead-induced release of N-acetyl-beta-D-glucosaminidase from perfused rat kidney

Urinary N-acetyl-beta-D-glucosaminidase (NAG) had been shown to be a useful early marker of renal injury such as lead nephrotoxicity. This study investigated the effect of lead acetate on nephrotoxicity and its correlation with the nitric oxide (NO) system by determining the NAG release in perfused rat kidney. Lead acetate caused a time and concentration-dependent increase in enzymuria. The effect of concurrent perfusion with lead and L-arginine (L-arg) or L-N(G)-nitro arginine methyl ester (L-NAME) [substrate and inhibitor of NO synthase respectively] in the perfusion fluid was also studied by measuring NAG activity in the perfusate kidney rat. L-arg (2 mM) has significantly decreased the lead-induced NAG release (P < 0.001), and L-NAME (0.1 mM) has significantly increased the lead-induced enzyme release in a time-dependent manner (P < 0.001). Moreover, histological studies using light microscope showed that some of the epithelial cells of the proximal convoluted tubules are degenerated or necrotic and desquamated into the lumens in rat treated with lead acetate. This change occurs at 50 microg/dl of lead acetate and was increased by addition of L-NAME to lead acetate. However, addition of L-arg had no effect on histology of lead nephrotoxicity. This may suggest that lead may interfere with the NO system in rat kidney.

Lead exposure in the general population of the Metropolitan Area of Barcelona: blood levels and related factors

A cross-sectional study was conducted on 254 individuals not occupationally exposed to lead to determine the degree of lead exposure in the general population of the Metropolitan Area of Barcelona. Blood lead levels (BPb) were analysed by atomic absorption spectrophotometry and zinc protoporphyrin (ZPP) by haemofluorimetry. Blood lead levels were analysed with respect to individuals' age, sex, area of residence, the season of the year the blood was drawn and ZPP. Mean blood lead in our series was 0.22 +/- 0.011 mumol/l (mean +/- S.E.); no significant differences were found with respect to area of residence, sex or season. A linear relationship was observed between BPb and individuals' age (BPb = 0.08 + 0.05 x age; r = 0.37). The prevalence of lead intoxication (BPb > 0.48 mumol/l) was 7.1%. No linear relationship was observed between BPb and ZPP. ZPP determination does not appear to be a good screening method for lead intoxication since it presents low specificity and sensitivity values with an area below the ROC curve similar to the null value line (area below the curve = 0.5052, IC 95% = 0.443-0.568). We conclude that lead exposure does not constitute a serious health problem in the area studied, since BPb levels found are far below the toxic limit and the prevalence of intoxication is similar to that reported in other studies conducted in other developed countries.

Effect of prenatal and postnatal exposure to lead on kidney function in male and female rats

The effect of 5 months' exposure to 0.5% lead acetate in drinking water on the kidney function of developing rats was studied. In both sexes, lead exposure produced a significant elevation of the kidney weight and after 3 months' treatment both male and female rats showed signs of tubular impairment. In male rats increased beta 2-microglobulin and lactate dehydrogenase excretion was observed. Lysozyme was increased after 5 months of exposure. No changes were observed in total proteins and albumin excretion. Female rats showed a significantly increased excretion of beta 2-microglobulin from 3 months onwards, while lactate dehydrogenase increased only at the end of 3 months and total proteins after 5 months of exposure. No changes were observed in lysozyme and albumin excretion. Thus, the results suggest that lead exposure produces changes in the renal tubular function of developing rat. There is no sex difference in the nephrotoxicity of lead. Comparison with our previous studies suggests that exposure to lead starting at weaning is more renotoxic than exposure starting 2 months later. However, prenatal exposure might also have been a contributory factor.

Effects of acidification on the availability of toxic metals and calcium to wild birds and mammals

The effects of acidification on wildlife inhabiting aquatic or semi-aquatic environments are reviewed, with particular reference to the possibility for increased dietary exposure to Hg, Cd, Pb and/or Al, and decreased availability of essential dietary minerals such as Ca. It is concluded that: (1) piscivores risk increased exposure to dietary methyl-Hg in acidified habitats, and Hg concentrations in prey may reach levels known to cause reproductive impairment in birds and mammals; (2) piscivores do not risk increased exposure to dietary Cd, Pb or Al because these metals are either not increased in fish due to acidification, or increase are trivial from a toxicological perspective; (3) insectivores and omnivores may, under certain conditions, experience increased exposure to toxic metals in some acidified environments. Exposure levels are likely to be sufficiently low, however, that significant risks to health or reproduction are unlikely. More importantly, these wildlife species may experience a drastic decrease in the availability of dietary Ca due to the pH-related extinction of high-Ca aquatic invertebrate taxa (molluscs, crustaceans). Decreased availability of dietary Ca is known to adversely affect egg laying and eggshell integrity in birds, and the growth of hatchling birds and neonatal mammals. Acidification-related changes in the dietary availability of other essential elements, such as Mg, Se and P, have not been established and require further investigation; (4) herbivores may risk increased exposure to Al and Pb, and perhaps Cd, in acidified environments because certain macrophytes can accumulate high concentrations of these metals under acidic conditions. The relative importance of pH in determining the metal concentrations of major browse species, and the toxicological consequences for herbivores wildlife, is not well established and requires further study. A decreased availability of dietary Ca is also likely for herbivores inhabiting acidified environments.

Interaction of lead acetate with atrial natriuretic factor in rats

Lead exposure alters cardiovascular function and has been implicated in the etiology of hypertension. Therefore it was of interest to study the short term effect of lead treatment on atrial natriuretic factor (ANF), a hormone which produces vascular smooth muscle relaxation and natriuresis. Male Sprague Dawley rats were randomly divided into 5 groups containing 4 animals each and injected intraperitoneally with normal saline (control), 0.01, 0.1, 0.5 or 1.0 mg/kg of body weight with lead acetate solution twice a day for 7 days, and then maintained for a period of 30 days. During this period water consumption and urine volume were measured daily. At the end of the 30 day period, immunoreactive levels of ANF in hypothalamus, atria and plasma were measured by radioimmunoassay. Lead treatment did not alter water consumption, but significantly decreased urine output. At all doses, lead produced a decrease in hypothalamic content of ANF and slightly increased atrial levels. The content of ANF in plasma was decreased. The changes in ANF content indicate that lead interacts with the hormonal regulation of the cardiovascular system and these observations may relate to the cardiovascular toxicity of this heavy metal.