Impact of the California lead ammunition ban on reducing lead exposure in golden eagles and turkey vultures

Predatory and scavenging birds may be exposed to high levels of lead when they ingest shot or bullet fragments embedded in the tissues of animals injured or killed with lead ammunition. Lead poisoning was a contributing factor in the decline of the endangered California condor population in the 1980s, and remains one of the primary factors threatening species recovery. In response to this threat, a ban on the use of lead ammunition for most hunting activities in the range of the condor in California was implemented in 2008. Monitoring of lead exposure in predatory and scavenging birds is essential for assessing the effectiveness of the lead ammunition ban in reducing lead exposure in these species. In this study, we assessed the effectiveness of the regulation in decreasing blood lead concentration in two avian sentinels, golden eagles and turkey vultures, within the condor range in California. We compared blood lead concentration in golden eagles and turkey vultures prior to the lead ammunition ban and one year following implementation of the ban. Lead exposure in both golden eagles and turkey vultures declined significantly post-ban. Our findings provide evidence that hunter compliance with lead ammunition regulations was sufficient to reduce lead exposure in predatory and scavenging birds at our study sites.     

Changes in hemorheological parameters due to lead exposure in female rats

Lead is an ubiquitous metal in the environment that induces a broad range of physiological, biochemical and behavioral dysfunctions. The purpose of this study was to investigate its effects on blood parameters and blood viscosity. Female rats (14 Wistar-Albino type) were divided into a control and a lead exposed group. Both groups were fed with the same standard food, but lead acetate was added to the drinking water of the experimental group for 5 weeks. At the end of the experimental period, blood samples were drawn from the abdominal aorta of the anaesthetized animals. Hematocrit (Hct %), hemoglobin (Hb), and the number of erythrocytes were determined, blood viscosity was measured with a rotational viscometer, and the lead concentration in blood was analyzed by means of flame atomic absorption spectrometry. The erythrocyte count, Hb and Hct % of the lead exposed group were found to be significantly lower than in the control group (p<0.01). The blood viscosity level was significantly higher compared to the control group (p<0.01). It can be concluded that increased lead concentrations in blood impair certain hemorheological mechanisms and increase blood viscosity.     

Study of the neurochemical alterations produced in discrete brain areas by perinatal low-level lead exposure

Although the neurotoxic effects of Pb are well documented, the subcellular mechanisms of this action in the central nervous system are not fully understood. The present work examines some neurochemical parameters in discrete brain areas of pups whose mothers were intoxicated via drinking water with lead (300 mg/L), from day 1 of pregnancy until postnatal day 12. Lead intoxication produced a significant reduction in the activity of the enzymes alkaline phosphatase and ATP-ase in the brain. Furthermore, the levels of adenine nucleotides were significantly altered by treatment, the striatum being the area more affected, whereas lead did not vary the levels of ATP, ADP and AMP in the hypothalamus. On the other hand, there was a general decrease in neurotransmitter levels in all areas, specially in the hippocampus. These data suggest that gestational and lactational exposure to low dose of lead could produce neurochemical changes in discrete brain areas which can be responsible for the neurophysiological and behavioral changes described in lead-intoxicated animals.     

Erythrocyte pyrimidine 5'-nucleotidase inhibition by acute lead exposure in neonatal rats

Inhibition by lead of erythrocyte pyrimidine 5'-nucleotidase (P5N) is thought to contribute to morphological abnormalities observed in red blood cells (RBC) of lead-exposed subjects. However, neither the mechanism of lead inhibition of P5N nor the relationship of this inhibition to blood lead levels attained in exposed subjects is known. In the present investigation, acute in vivo and in vitro lead acetate effects on erythrocyte P5N from 21-day-old rat pups were determined and were related to blood lead concentrations ascertained by atomic absorption spectrophotometry. Acute lead administration to rat pups resulted in a 16% to 21% reduction in erythrocyte P5N, with mean blood lead levels ranging from 77 to 108 micrograms/dl 24 hours later. Inhibition of erythrocyte P5N was linearly related to blood lead level (r = -0.67, P less than 0.05) following acute lead administration. Lead acetate addition to RBC preparations from 21-day-old rats resulted in concentration-dependent P5N inhibition which was comparable to that produced following acute in vivo exposure. The results indicate that acute P5N inhibition in lead-treated neonatal rats is due to noncompetitive P5N inhibition by lead. The inhibition of P5N produced by acute lead treatment is linearly related to blood lead concentrations.     

Lead poisoning in whooper and tundra swans

Six weak whooper swans (Cygnus cygnus) and two weak tundra swans (Cygnus columbianus) were found at Swamp Miyajima (Hokkaido, Japan) in May 1998. Anorexia, depression, green watery feces, pale conjunctiva, and anemia were observed. Radiographs showed from six to 38 suspected lead pellets in the gizzard. Blood lead concentrations were 2.5-6.7 microg/g (mean+/-SD=4.6+/-1.14 microg/g) on day 1. After blood collection, the birds were treated with calcium disodium ethylenediaminetetraacetate (CaEDTA) given intravenously and force fed. Despite treatment, seven birds died the next day. Green, bile-stained livers and pale or green kidneys were observed on necropsy. Microscopically, bile pigment was widespread in the liver and acid-fast intranuclear inclusion bodies were observed in renal tubular epithelium. Lead concentrations in livers and kidneys were 14.0-30.4 microg/g and 30.2-122 microg/g wet weight, respectively. Only one bird survived and this whooper swan continued to be treated with CaEDTA and activated charcoal. No lead shot was observed in the proventriculus and gizzard by radiography on day 64 and the blood lead concentration decreased from 2.9 microg/g to 0.09 microg/g during that same period. After 4 mo of rehabilitation, the whooper swan was returned to the wild. Lead intoxication continues to be a problem at Swamp Miyajima.     

Cytotoxic effects of lead on the endocrine and exocrine sexual function of pubescent male and female rats. Demonstration of apoptotic activity

This study deals with the impact of chronic exposure to lead on male and female fertility in rats. Male and female rats (3 months old) were fed on commercial tablets (SICO, Sfax). For drinking, some rats were given distilled water (T = controls), the other ones were given distilled water enriched with lead acetate, either 3 (P1 group) or 6 mg ml-1 (P2 group), for 15, 30, 45, 60 or 90 days. In male rats, absolute and relative weights of testis, epididymis, prostate and seminal vesicles were found to significantly decrease at day 15 in the P2 group and at day 45 in the P1 group. However, at day 60, these absolute and relative weights returned to control values. Lead-induced pathological changes in spermatogenesis were observed at day 15 by histological study: arrest of cell germ maturation, changes in the Sertoli cells, and presence of apoptotic cells revealed by borated toluidine blue in the testis. Presence of lead deposits was observed after histochemical staining using sodium rhodizonate. Serum testosterone level was found to be lowered at day 15 in both (P1) and (P2) groups, to display a peak at day 60, then to return to controls values, in spite of the continuation of the treatment. In female rats, absolute and relative weights of ovary and uterus were found unchanged. The vaginal smears practiced in females revealed the oestrus phase in all groups. Exposed females were mated with control males, and fecundity was assessed 15 days later by counting the number of pregnancies and the number of concepti per pregnancy. Fertility was found to be reduced in females of P1 and P2 groups as compared to control females (T group). Lead level in blood was found to be poorly correlated with the level of poisoning, whereas lead accumulation in tail was found to be dose-dependent. Therefore, lead accumulation in tail appears as a more reliable biomarker of exposure to lead. In summary, our study shows that chronic exposure to lead causes a double sexual disorder in rats: first, disorder deals with the hormonal function, which is affected at the early stages of poisoning, but is rapidly corrected; second, disorder deals with the genital tract, affecting the testis and the ovary, resulting in a reduced fertility in both P1 and P2 females, in spite of the presence of a normal oestrus. The cytotoxic effect of lead in males seems to be related to an apoptotic process.     

Interactions between tissue uptake of lead and iron in normal and iron-deficient rats during development

Environmental lead intoxication, which frequently causes neurological disturbances, and iron deficiency are clinical problems commonly found in children. Also, iron deficiency has been shown to augment lead absorption from the intestine. Hence, there is evidence for an interaction between lead and iron metabolism which could produce changes in lead and iron uptake by the brain and other tissues. These possibilities were investigated using 15-, 21-, and 63-old rats with varying nutritional iron and lead status. Dams were fed diets containing 0 or 3% lead-acetate and 0.2% lead-acetate in the drinking water. After weaning, 0.2% lead-acetate in the drinking water became the sole source of dietary lead. Measurements were made of tissue lead and nonheme iron levels and the uptake of⁵⁹Fe after intravenous injection of transferrin-bound⁵⁹Fe. Iron deficiency was associated with increased intestinal absorption of lead as indicated by blood and kidney lead levels in rats exposed to dietary lead. However, iron deficiency did not increase lead deposition in the brain, and in all rats brain lead levels were relatively low (<0.1 μg/g). Lead concentrations in the liver were below 2 μg/g, whereas kidneys had almost 20 times this concentration. Animals with iron deficiency had lower liver iron levels and had increased brain⁵⁹Fe uptake in comparison to control rats. However, iron levels in brain and kidneys were unaffected by lead intoxication regardless of the animal's iron status.⁵⁹Fe uptake rates were also unaffected by lead, but increased rates of uptake were apparent in iron-deficient rats. Lead did increase liver iron levels in all iron-adequate rats, but iron deficiency had little effect. It is concluded that, compared with other tissues, the blood-brain barrier largely restricts lead uptake by the brain and that the uptake that does occur is unrelated to the iron status of the animal. Also, the level of lead intoxication produced in this investigation did not influence iron uptake by the brain and kidneys, but liver iron stores could be incresed if iron levels were already adequate.     

Role of selenium against lead toxicity in male rats

Male albino rats were intramuscularly administered a single dose of lead acetate (100 μmol/kg b.wt). Another group of rats were injected with sodium selenite (10 μmol/kg b.wt) before lead intoxication. After 3 and 24 hours, lead treatment resulted in significant increases in acid and alkaline phosphatases, GOT and GPT, total proteins, and cholesterol in serum. The total triglycerides in serum was decreased after 24 hours of intoxication. Lead treatment also produced significant elevation of lipid peroxidation in liver and kidney. The antioxidant capacity of hepatic and renal cells in terms of the activities of superoxide dismutase, glutathione reductase, and glutathione content was diminished. It appears from these results that lead may exert its toxic effect via peroxidative damage to renal and hepatic cell membranes after 24 hours. Selenium administration prior to lead injection produced pronounced prophylactic action against lead effects, and it is observed that selenium enhances the endogenous antioxidant capacity of the cells by increasing the activities of the superoxide dismutase and glutathione reductase and the glutathione content. As a result, the lipid peroxidation was decreased in both liver and kidney. © 1998 John Wiley & Sons, Inc. J Biochem Mol Toxicol 12: 345–349, 1998     

Low-level lead exposure increases systolic arterial pressure and endothelium-derived vasodilator factors in rat aortas

Chronic lead exposure induces hypertension and alters endothelial function. However, treatment with low lead concentrations was not yet explored. We analyzed the effects of 7 day exposure to low lead concentrations on endothelium-dependent responses. Wistar rats were treated with lead (1st dose 4 μg/100 g, subsequent dose 0.05 μg/100 g, i.m. to cover daily loss) or vehicle; blood levels attained at the end of treatment were 9.98 μg/dL. Lead treatment had the following effects: increase in systolic blood pressure (SBP); reduction of contractile response to phenylephrine (1 nM-100 μM) of aortic rings; unaffected relaxation induced by acetylcholine (0.1 nM-300 μM) or sodium nitroprusside (0.01 nM-0.3 μM). Endothelium removal, N(G)-nitro-L-arginine methyl ester (100 μM) and tetraethylammonium (2 mM) increased the response to phenylephrine in treated rats more than in untreated rats. Aminoguanidine (50 μM) increased but losartan (10 μM) and enalapril (10 μM) reduced the response to phenylephrine in treated rats. Lead treatment also increased aortic Na(+)/K(+)-ATPase functional activity, plasma angiotensin-converting enzyme (ACE) activity, protein expression of the Na(+)/K(+)-ATPase alpha-1 subunit, phosphorylated endothelial nitric oxide synthase (p-eNOS), and inducible nitric oxide synthase (iNOS). Our results suggest that on initial stages of lead exposure, increased SBP is caused by the increase in plasma ACE activity. This effect is accompanied by increased p-eNOS, iNOS protein expression and Na(+)/K(+)-ATPase functional activity. These factors might be a compensatory mechanism to the increase in SBP.     

Erythrocyte pyrimidine 5′-nucleotidase inhibition by acute lead exposure in neonatal rats

Inhibition by lead of erythrocyte pyrimidine 5′-nucleotidase (P5N) is thought to contribute to morphological abnormalities observed in red blood cells (RBC) of lead-exposed subjects. However, neither the mechanism of lead inhibition of P5N nor the relationship of this inhibition to blood lead levels attained in exposed subjects is known. In the present investigation, acute in vivo and in vitro lead acetate effects on erythrocyte P5N from 21-day-old rat pups were determined and were related to blood lead concentrations ascertained by atomic absorption spectrophotometry. Acute lead administration to rat pups resulted in a 16% to 21% reduction in erythrocyte P5N, with mean blood lead levels ranging from 77 to 108 μg/dl 24 hours later. Inhibition of erythrocyte P5N was linearly related to blood lead level (r = ?0.67, P < 0.05) following acute lead administration. Lead acetate addition to RBC preparations from 21-day-old rats resulted in concentration-dependent P5N inhibition which was comparable to that produced following acute in vivo exposure. The results indicate that acute P5N inhibition in lead-treated neonatal rats is due to noncompetitive P5N inhibition by lead. The inhibition of P5N produced by acute lead treatment is linearly related to blood lead concentrations.     

Effects of lead on the renal response to extracellular volume expansion

Subacute lead exposure has been observed to inhibit the natriuretic response to isotonic saline expansion in adult female rats. Three-week exposure to 0.5% lead acetate in drinking water resulted in a moderately high blood lead concentration of 57 micrograms/100 ml and up to 60% inhibition of the natriuretic response to extracellular volume expansion. This ability of lead to inhibit natriuresis following volume expansion (an induced stress) may be a more sensitive index of lead poisoning than alterations of renal function in nonstressed animals. Lead exposure had no effect on GFR or plasma aldosterone concentrations, and in the presence of large doses of DOCA (a mineralocorticoid) this inhibitory effect of lead was still persistent. Amiloride completely blocked the antinatriuretic effect of lead in volume-expanded lead-poisoned animals, causing a twofold increase in water and electrolyte excretion while having minimal effects on volume-expanded controls. It is concluded that lead interferes with the action of a "third factor," controlling natriuresis.     

Reevaluation of a sensitive indicator of early lead exposure

A principal target for the environmental toxin lead (Pb) is porphobilinogen synthase (PBGS), a Zn-metalloenzyme necessary for heme biosynthesis. Measurement of blood Pb inhibited PBGS is the most sensitive indicator of subclinical Pb intoxication, but problems with the assay have diminished its use. This report identifies Pb as a slow acting inhibitor of PBGS. The activity of PBGS could change up to sixfold during an hourlong clinical assay of Pb contaminated blood, and activity is profoundly effected by the presence of serum proteins, such as albumin. When PBGS catalyzed PBG production is allowed to reach a steady state rate, kinetic data on purified PBGS support the hypothesis that Pb inhibition of PBGS results from direct substitution for Zn.     

Lead poisoning in zoo-dwelling primates

Lead intoxication was diagnosed in 42 primates at the National Zoological Park. Diagnoses were made clinically by the observation of signs of encephalopathy and the finding of 200 μg lead or more/100 ml blood, or postmortem by the presence of renal acid-fast intranuclear inclusion bodies and excess lead in liver specimens. Twenty-five of the primates had signs or lesions of lead encephalopathy. Lead poisoning was most common in the Cercopithecidae, and in the summer months. Lead encephalopathy was most frequent in juveniles. Leaded paint on the monkey cages was determined to be the source of poisoning. Blood studies revealed slight hypochromic anemia and immature and stippled erythrocytes. Postmortem lesions included acid-fast intranuclear inclusions in renal tubular and other epithelial cells; metaphyseal bone changes (lead lines); necrosis of striated muscle fibers; and other lesions. Treatment of one monkey for encephalopathy was attempted and proved successful.     

Removal of lead from solution by the non-viable biomass of the water fern Azolla filiculoides

Non-viable biomass of the aquatic fern, Azolla filiculoides, removed up to 93 mg lead/g biomass from solution. Lead removal varied from 30% of the initial lead concentration at pH 1.5 to approximately 95% at pH values of 3.5 and 4.5. Lead removal decreased to 30% of the initial lead concentration if the lead concentration was initially over 400 mg/l. Lead removal remained at approximately 90% between 10 °C and 50 °C. Biomass concentration (4–8 mg/l) had little effect on lead removal. © Rapid Science Ltd. 1998     

Oxidative damage in liver after perinatal intoxication with lead and/or cadmium

Lead acetate (300 mg Pb/L) and/or cadmium acetate (10mg Cd/L) in blood and liver were administrated as drinking water to pregnant Wistar rats from day 1 of pregnancy to parturition (day 0) or until weaning (day 21), to investigate the toxic effects in blood and in the liver. Both metals produced mycrocitic anaemia in the pups as well as oxidative damage in the liver, as suggested by the significant increase in TBARS production and the high catalase activity. Moreover, intense alkaline and acid phosphatase activity, used as biomarkers of liver adaptation to damaging factors, was observed. In addition, the toxikinetics are different for Pb and Cd: while Cd is a hepatotoxic from day 0, Pb is not until day 21. Finally, simultaneous perinatal administration of both metals seems to protect, at least, in the liver TBARS production against the toxicity produced by Cd or Pb separately.     

Chelation of lead during co-exposure to ethanol

Efficacy of calcium disodium EDTA, D-penicillamine (DPA), 2,3 dimercaptosuccinic acid (DMSA), and alpha-mercapto-beta-(2-furyl) acrylic acid (MFA) to reduce the body burden of lead and restore the altered biochemical variables in lead or lead + ethanol administered rats was investigated. The investigation was aimed to suggest suitable prophylaxis of lead intoxication prevalent among workers co-exposed to lead and alcohol ingestion. Administration of lead (10 mg/kg, oral, once daily for 8 weeks) produced a significant inhibition in the activity of blood delta-aminolevulinic acid dehydratase (ALAD), elevation in the blood zinc protoporphyrin (ZPP) and urinary elimination of lead and delta-aminolevulinic acid (ALA). Lead contents of blood, liver, kidney and brain were also significantly higher than the normal control. The above changes were more marked in animals co-exposed to lead + ethanol (20% in drinking water) compared to lead alone. All the chelators were effective in increasing the urinary lead elimination, reducing the above biochemical alterations and lead contents of tissues. The order of effectiveness being DMSA greater than Calcium disodium EDTA greater than DPA greater than MFA. However, the protection was more noticeable in animals treated with lead alone than with lead and ethanol.     

The effects of early life lead exposure on the expression of P2X7 receptor and synaptophysin in the hippocampus of mouse pups

The present study was undertaken to investigate the effects of maternal lead exposure on expression of P2X7 receptor and synaptophysin in the hippocampus of mice offspring. Lead exposure initiated from beginning of gestation to weaning. Lead acetate administered in drinking solutions was dissolved in distilled deionized water at the concentrations of 0.1%, 0.5% and 1% groups, respectively. On the 21st postnatal day, the Pb levels were also determined by graphite furnace atomic absorption spectrometry. The expression of P2X7 receptor and synaptophysin in hippocampus was examined by immunohistochemistry and Western blotting. The lead levels in blood and hippocampus of all lead exposure groups were significantly higher than that of the control group (P < 0.05). Compared with the control group, the expression of P2X7 receptor was increased in lead exposed groups (P < 0.05), but the expression of synaptophysin was decreased (P < 0.05). The high expression of P2X7 receptor and low expression of synaptophysin in the hippocampus of pups may contribute to the neurotoxicity associated with maternal Pb exposure.     

Effects of tin and lead on organ levels of essential minerals in rabbits

The effect of tin and lead on levels of essential metals (Zn, Cu, Ca, Fe) in rabbit tissues was compared in relation to the route of administration. Animals received intraperitoneally, or per os, SnCl2 (2 mg Sn/kg) or Pb(CH3COO)2 (3.5 mg Pb/kg) every day for 5 d or for 1 mo. Copper, zinc, iron, and calcium were determined by AAS in the liver, kidneys, spleen, brain, bone marrow, and blood; lead and tin concentration were measured in the blood of animals. Tin and lead administered per os caused either no changes or the decreased concentration of endogenous metals in several tissues. The other route of administration (ip) of both metals generally contributed to the increased storage of essential elements. Blood tin levels of tin treated animals were only about less than or equal to 1/10 of blood lead concentrations of rabbits exposed to lead.     

Interrelation of delta-aminolevulinic acid and brain myelin proteins as affected by benzene and lead

An experimental model of subacute lead and benzene intoxication was induced in rabbits. It increased significantly delta-aminolevulinic acid (14C-ALA) incorporation into CNS myelin. ALA stably fixes on myelin proteins, especially Wolfgram proteins. In spite of this about one half of ALA incorporated into myelin linked with its basic proteins. Lead and benzene intoxication cause changes in the proportion of the basic fractions of myelin proteins. The amount of basic proteins increases, while the amount of proteolipid and Wolfgram proteins decreases. Lead and especially benzene intoxication decreases exogenous ALA insertion into basic proteins and proteolipid proteins, with ALA fixation on Wolfgram proteins remaining unchanged.     

Effects of sub-chronic low-level lead exposure on the homeostasis of copper and zinc in rat tissues

Information about the health risks or the subtle adverse health effects that might be associated with low-level lead exposure on micronutrient metabolism are scarce in the literature. The present work investigated the subtle adverse health effects of exposure to progressively low levels of lead on the metabolism of two micronutrients, copper and zinc in different tissues of the rat. Rats were exposed to 200, 300 and 400 ppm lead in their drinking water for 12 weeks. Lead, copper and zinc concentrations were determined in blood, liver, kidney, heart, spleen and brain of the animals. While the imbalance in zinc metabolism was characterized by a deposition of zinc in the kidney and to a lesser extent in the heart of the animals, imbalance in copper metabolism was characterized by a depletion of blood and splenic copper concentrations as well as renal and cardiac accumulation of copper. Hepatic and brain copper and zinc contents, together with blood zinc were not affected by the 12-week lead exposure. A linear relationship was observed between lead dose and lead accumulation in the spleen, whereas a non-linear relationship was observed between lead dose and lead accumulation in blood, liver, kidney and heart. Our findings indicate that exposure to progressively low-level lead concentrations results in imbalance in copper and zinc in the organism and this might be a factor in propensity toward behavioral disorders observed in lead exposure.