Gestational administration of cadmium alters the neurotransmitter levels in newborn rat brains

Association between prenatal cadmium exposure and child development: The Japan Environment and Children's study

Cadmium is a heavy metal that can be found in soil, air, food, and water. Cadmium has toxic effects on the kidneys, bones, and respiratory system. Prenatal exposure to cadmium has been found to affect the mental development of children, but inconsistent results have been found in different studies. Therefore, it is unknown that prenatal cadmium exposure associated with child development after birth. To elucidate whether cadmium affect the child development or not, we analyzed nation-wide cohort study data, the Japan Environment and Children's Study. Prenatal cadmium concentrations in blood from mothers in the second or third trimester were determined by inductively coupled plasma mass spectrometry. Child development was evaluated using "Ages and Stages" questionnaires. The association between cadmium and child development were investigated by performing logistic regression analyses, multinomial logistic regression analyses and generalized linear mixed model using the child development parameters as dependent variables and the cadmium concentrations in maternal blood as the independent variable. There were significant associations between the cadmium concentration and child development at 6 months, 1 year, and 1.5 years after birth. However, the effect had disappeared at 2 years after birth or later. The number of developmental delays was positively associated with the cadmium concentration after adjusting individual difference. The results indicate that prenatal exposure affects child development, but the effect decreases with age.

Exposure to aluminium causes behavioural alterations and oxidative stress in the brain of adult zebrafish

Aluminium (Al) water pollution is an increasing environmental problem. Accordingly, this study aimed to find out more about its toxic effects on aquatic organisms. Adult zebrafish were exposed to 11 mg/L of Al and the behavioural responses and its correlation with brain oxidative stress, antioxidant-defences, changes in metabolism and neurotransmission were assessed at 10, 15 and 20 days of exposure. The behavioural and locomotory responses, suggest an increase in the anxiety state, especially observed in animals exposed to Al for 15 days. The reactive oxygen species increased in a time-dependent trend, while the oxidative damage varied over exposure time. The activity of antioxidant enzymes, as superoxide dismutase, glutathione peroxidase and glutathione S-transferases, and the metallothioneins levels increased after short-term exposures and tended to decrease or stabilize at longer times. The results contribute to understand the toxic mechanisms activated by Al highlighting correlations like behavioural disorders and oxidative state.

Alleviated Actions of Plantago albicans Extract on Lead Acetate-Produced Hepatic Damage in Rats Through Antioxidant and Free Radical Scavenging Capacities

The aim of this study was to explore the possible protective mechanisms and to determine the antioxidant capacity of phenolic compounds extracted from Plantago albicans against lead acetate-induced hepatic injury. High performance liquid chromatography-photo diode array/electrospray ionization-mass spectrometry (HPLC-PDA/ESI-MS) assay was used to identify the P. albicans extract phenolic compounds. Animals received 100 mg of lead acetate/kg of body weight (bw) in the drinking water for a period of 30 days. The other groups of rats were orally administered with silymarin (300 mg/kg bw) or the P. albicans extract at two doses (100 and 300 mg/kg of bw), once daily, by gastric gavage for the same time. The P. albicans exhibited high total phenolic, flavonoid, and anthocyanin contents. The antioxidant in vitro activity demonstrated that the P. albicans exhibits an important effect against deleterious reactive species. The in vivo results showed that P. albicans prevented the lead acetate-induced significant changes on serum and liver lipid levels. In contrast, P. albicans succeeded in improving the biochemical parameters of serum and liver bringing them closer to the normal values of the control group. It also significantly promoted (P < .05) pro-inflammatory cytokines (TNF-α, IL-6, and NF-κB) in the liver of the experimental animals. The evaluated sample with HPLC-PDA/ESI-MS method showed to contain 10 dominant polyphenols, 2 hydroxycinnamic acids (p-coumaric acid and chlorogenic acids), 4 flavones (Apigenin, Luteolin, Cirsiliol, and Luteolin-7-O-rutinoside), and an anthocyanin (cyanidin-3-glucoside). Hence, it can be concluded that P. albicans could be a potent source of health-beneficial phytochemicals providing a novel therapy to protect liver against lead exposure.

Analysis of tail coiling activity of zebrafish (Danio rerio) embryos allows for the differentiation of neurotoxicants with different modes of action

In (eco)toxicology, there is a critical need for efficient methods to evaluate the neurotoxic potential of environmental chemicals. Recent studies proposed analysis of early coiling activity in zebrafish embryos as a powerful tool for the identification of neurotoxic compounds. In order to demonstrate that the analysis of early tail movements of zebrafish embryos allows for the discrimination of neurotoxicants acting via different mechanisms, the present study investigated the effects of four different neurotoxicants on the embryogenesis (fish embryo toxicity test) and early tail coiling movements of zebrafish embryos. Cadmium predominantly increased the frequency of tail coiling at the late pharyngula stage. Dichlorvos delayed embryonic development and caused convulsive tail movements resulting in prolonged duration of tail coils. Embryos exposed to teratogenic concentrations of fluoxetine and citalopram displayed absence of spontaneous tail movements at 24 h post-fertilization. In contrast, a non-teratogenic test concentration of citalopram decreased coiling frequency at multiple time points. Results demonstrated that the analysis of tail coiling movements of zebrafish embryos has the potential to discriminate neurotoxic compounds with different primary modes of action. In addition, chemical-induced effects on coiling activity were shown to potentially overlap with effects on embryogenesis. Further studies are needed to clarify the interplay of unspecific developmental toxicity of neurotoxic chemicals and effects resulting from specific neurotoxic mechanisms.

Prenatal Exposure to Cadmium During Organogenesis Impairs Memory in Young Rats

Pregnant rats were treated with 0.3 and 0.6 mg cadmium (CdCl₂)/kg injected subcutaneously on a daily basis from gestational day 7 to day 15 (organogenesis period). One control group was not injected and other received saline. The 45-day-old offspring were tested in a step-down inhibitory avoidance to evaluate short-term and long-term memory and in a radial maze for the study of spatial memory. These studies showed that gestational exposure to 0.6 mg Cd/kg produced in the male offspring a significant impairment in the retention of long-term memory evaluated 24 hours after training in the step-down inhibitory avoidance. The radial maze also demonstrated that the male offspring prenatally exposed to 0.6 mg Cd presented a significant deficit in the retention of spatial memory evaluated 42 days after training. These results demonstrate that the exposure to Cd during organogenesis may affect the retention of some types of memory.

Disruption of the zinc metabolism in rat fœtal brain after prenatal exposure to cadmium

This study was carried out to investigate the effects of maternal Cd and/or Zn exposure on some parameters of Zn metabolism in fetal brain of Wistar rats. Thus, female controls and other exposed by the oral route during the gestation period to Cd (50 mg CdCl2/L) and/or Zn (ZnCl2 60 mg/L) were used. The male fetuses at age 20 days of gestation (GD20) were sacrificed and their brains were taken for histological, chemical and molecular analysis. Zn depletion was observed in the brains of fetuses issued from mothers exposed to Cd. Histological analysis showed that Cd exposure induces pyknosis in cortical region and CA1 region of the hippocampus compared to controls. Under Cd exposure, we noted an overexpression of the genes coding for membrane transporter involved in the intracellular incorporation of Zn (ZIP6) associated with inhibition of that encoding the transporters involved in the output of the Zn into the extracellular medium (ZnT1 and ZnT3). A decrease in the expression of the gene encoding the neuro-trophic factor (BDNF) associated with overexpression of the encoding the metal regulatory transcription factor 1 (MTF1), factor involved in the homeostasis of Zn, was also noted in Cd group. Interestingly, Zn supply provided a total or partial restauration of the changes induced by the Cd exposure. The depletion of brain Zn contents as well as the modification of the profile of expression of genes encoding membrane Zn transporters, suggest that the toxicity of Cd observed in fetal brain level are mediated, in part, by impairment of Zn metabolism.

Cadmium-induced toxicity is rescued by curcumin: A review

Cadmium (Cd) is one of the most common environmental and occupational heavy metals with extended distribution. Exposure to Cd may be associated with several deleterious consequences on the liver, bones, kidneys, lungs, testes, brain, immunological, and cardiovascular systems. Overproduction of reactive oxygen species (ROS) as the main mechanism behind its toxicity causes oxidative stress and subsequent damages to lipids, proteins, and DNA. Therefore, antioxidants along with chelating agents have shown promising outcomes against Cd-induced toxicity. Curcumin with various beneficial effects and medical efficacy has been evaluated for its inhibitory activities against biological impairments caused by Cd. Thus, this article is intended to address the effectiveness of curcumin against toxicity following Cd entry. Curcumin can afford to attenuate lipid peroxidation, glutathione depletion, alterations in antioxidant enzyme, and so forth through scavenging and chelating activities or Nrf2/Keap1/ARE pathway induction. © 2017 BioFactors, 43(5):645-661, 2017.

Anxiety and memory deficits induced by tannery effluent in C57BL/6J female mice

This study aimed to evaluate the behavior of female C57Bl/6J mice exposed to tannery effluents diluted in drinking water. Female mice were divided into a control group, in which the animals received only drinking water, and experimental groups, which received raw tannery effluent in 7.5 and 15 % concentrations diluted in water (period of 60 days). In the last experimental week, the mice (in diestrus phase) were subjected to different behavioral tests: elevated plus-maze, open-field test, forced swim test, and object recognition test. Our data demonstrated that exposure to tannery effluent increased the anxiety index of animals and decreased the locomotion ratio in the central quadrants/total, indicating an increase in anxiety-like behavior. Regarding the forced swim test, we did not observe changes in the evaluated behaviors. There were no statistically significant differences in the recognition index of the novel and familiar object in the groups exposed to tannery effluent compared with the control group, indicating a possible influence of the constituents of tannery effluent on cognition. Thus, our findings support the hypothesis that effluents, containing neurotoxic substances, could cause behavioral disruptions in female C57Bl/6J mice.

Programmed Effects in Neurobehavior and Antioxidative Physiology in Zebrafish Embryonically Exposed to Cadmium: Observations and Hypothesized Adverse Outcome Pathway Framework

Non-communicable diseases (NCDs) are a major cause of premature mortality. Recent studies show that predispositions for NCDs may arise from early-life exposure to low concentrations of environmental contaminants. This developmental origins of health and disease (DOHaD) paradigm suggests that programming of an embryo can be disrupted, changing the homeostatic set point of biological functions. Epigenetic alterations are a possible underlying mechanism. Here, we investigated the DOHaD paradigm by exposing zebrafish to subtoxic concentrations of the ubiquitous contaminant cadmium during embryogenesis, followed by growth under normal conditions. Prolonged behavioral responses to physical stress and altered antioxidative physiology were observed approximately ten weeks after termination of embryonal exposure, at concentrations that were 50–3200-fold below the direct embryotoxic concentration, and interpreted as altered developmental programming. Literature was explored for possible mechanistic pathways that link embryonic subtoxic cadmium to the observed apical phenotypes, more specifically, the probability of molecular mechanisms induced by cadmium exposure leading to altered DNA methylation and subsequently to the observed apical phenotypes. This was done using the adverse outcome pathway model framework, and assessing key event relationship plausibility by tailored Bradford-Hill analysis. Thus, cadmium interaction with thiols appeared to be the major contributor to late-life effects. Cadmium-thiol interactions may lead to depletion of the methyl donor S-adenosyl-methionine, resulting in methylome alterations, and may, additionally, result in oxidative stress, which may lead to DNA oxidation, and subsequently altered DNA methyltransferase activity. In this way, DNA methylation may be affected at a critical developmental stage, causing the observed apical phenotypes.

Neurotoxicants, Micronutrients, and Social Environments

SUMMARY—Systematic research evaluating the separate and interacting impacts of neurotoxicants, micronutrients, and social environments on children's cognition and behavior has only recently been initiated. Years of extensive human epidemiologic and animal experimental research document the deleterious impact of lead and other metals on the nervous system. However, discrepancies among human studies and between animal and human studies underscore the importance of variations in child nutrition as well as social and behavioral aspects of children's environments that mitigate or exacerbate the effects of neurotoxicants.

In this monograph, we review existing research on the impact of neurotoxic metals, nutrients, and social environments and interactions across the three domains. We examine the literature on lead, mercury, manganese, and cadmium in terms of dispersal, epidemiology, experimental animal studies, effects of social environments, and effects of nutrition.

Research documenting the negative impact of lead on cognition and behavior influenced reductions by the Center for Disease Control in child lead-screening guidelines from 30 micrograms per deciliter (μg/dL) in 1975 to 25 μg/dL in 1985 and to 10 μg/dL in 1991. A further reduction is currently being considered. Experimental animal research documents lead's alteration of glutamate-neurotransmitter (particularly N-methyl-D-aspartate) activity vital to learning and memory. In addition, lead induces changes in cholinergic and dopaminergic activity. Elevated lead concentrations in the blood are more common among children living in poverty and there is some evidence that socioeconomic status influences associations between lead and child outcomes. Micronutrients that influence the effects of lead include iron and zinc.

Research documenting the negative impact of mercury on children (as well as adults) has resulted in a reference dose (RfD) of 0.1 microgram per kilogram of body weight per day (μg/kg/day). In animal studies, mercury interferes with glutamatergic, cholinergic, and dopaminergic activity. Although evidence for interactions of mercury with children's social contexts is minimal, researchers are examining interactions of mercury with several nutrients.

Research on the effects of cadmium and manganese on child cognition and behavior is just beginning. Experimental animal research links cadmium to learning deficits, manganese to behaviors characteristic of Parkinson's disease, and both to altered dopaminergic functioning.

We close our review with a discussion of policy implications, and we recommend interdisciplinary research that will enable us to bridge gaps within and across domains.

Cadmium neurotoxicity to a freshwater planarian

Although freshwater planarians are evolutionarily primitive, they are some of the simplest bilateral animals possessing integrated neural networks similar to those in vertebrates. We attempted to develop planarian Dugesia japonica as a model for investigating the neurotoxicity of environmental pollutants such as cadmium (Cd). This study was therefore designed to study the effects of Cd on the locomotor activity, neurobehavior, and neurological enzymes of D. japonica. After planarians were exposed to Cd at high concentrations, altered neurobehavior was observed that exhibited concentration-dependent patterns. Morphological alterations in Cd-treated planarians included irregular shape, body elongation, screw-like hyperkinesia, and bridge-like position. To study the direct effects of Cd on neurological enzymes, tissue homogenates of planarians were incubated in vitro with Cd before their activity was measured. Results showed that acetylcholinesterase (AChE), adenosine triphosphatase (ATPase), and monoamine oxidase A (MAO-A) activities were inhibited in a concentration-dependent manner. MAO-B activity was significantly induced by Cd at low concentrations and inhibited at high concentrations. Changes in the in vivo activity of AChE and ATPase were also found after planarians were treated with Cd at a sublethal concentration (5.56 μM). These observations indicate that neurotransmission systems in planarians are disturbed after Cd exposure.

Effects of maternal cadmium administration on development of monoaminergic, GABAergic and glutamatergic systems

The effects of maternal exposure to 10mgCd/l (as cadmium acetate) in drinking water during gestation and lactation on the development of monoaminergic and aminoacidergic systems were studied in discrete brain areas of the pups: striatum, cerebral cortex, dorsal hippocampus and basal-medial hypothalamus. Hippocampal levels of serotonin and 5-hydroxyindolacetic acid were significantly reduced in rats exposed to Cd whereas the dopamine content was not significantly affected by Cd. Glutamate concentration decreased in hypothalamus and increased in hippocampus, while gamma-aminobutiric acid content decreased only in cerebral cortex. The present results demonstrate that maternal exposure to 10mg/l of Cd leads to neurochemical disturbances on serotoninergic and aminoacidergic systems during development.

Calcium and zinc supplementation protects lead (Pb)-induced perturbations in antioxidant enzymes and lipid peroxidation in developing mouse brain

Several studies have implicated oxidative stress as one of the important mechanisms of toxic effects of lead (Pb). In the present study we tested the beneficial effects of calcium (Ca2+) and zinc (Zn2+) in protecting the Pb-induced oxidative stress in the brains of developing and adult mice. Mice were lactationally exposed to 0.2% Pb and supplemented with either calcium (Ca2+) or zinc (Zn2+) and the mitochondrial antioxidant enzymes [superoxide dismutase (SOD), xanthine oxidase (XO) and catalase (CAT)] and lipid peroxidation (LP) were analyzed in cortex, hippocampus, cerebellum and medulla of brains excised on postnatal day (PND) 14, 21, 28 and 3 months. The levels of free radicals were measured using direct Electron Paramagnetic Resonance (EPR) spectroscopy. Exposure to Pb resulted a significant decrease in the activities of SOD, XO and CAT while the LP levels were significantly increased in different brain regions. Evaluation of EPR signals and g-values showed abundant accumulation of free radicals in different regions of the brain following Pb exposure. Interestingly the supplementation with Ca2+ or Zn2+ reversed the Pb-induced effects on antioxidant enzymes, LP and free radical formation; however Zn2+ supplementation appeared to be more protective. These findings strongly support that zinc and calcium supplementation significantly protect the Pb-induced oxidative stress, a major contributing factor to neurotoxicity.

Assessment of Cu (II)-bearing montmorillonite on Cd adsorption

The abilities of montmorillonite (MMT) and Cu (II)-bearing montmorillonite (Cu-MMT) for adsorption of Cd from aqueous solutions have been studied at different optimized conditions of shaking time, pH value, and initial concentration, respectively. The results showed that the adsorbability of Cu-MMT onto Cd is stronger than the MMT. The amount of Cu-MMT necessary to remove Cd from solution was about 0.5 g for 100-200 mg/L Cd solution at a pH of 4.0. The maximum adsorption (94%) was 20 min of shaking time using Cu-MMT as adsorbent. The maximum adsorption of Cd = 95% at a pH of 4.0. By increasing the initial concentration, the adsorption amount of Cd onto Cu-MMT increased. Animal experiment of this study indicated that the addition of Cu-MMT to the Cd-contaminated diet of pigs reduced significantly the Cd levels in tissues (p < 0.05) and increased contents in feces (p < 0.01), improving the safety of animal products. Thus, the overall results established the use of Cu-MMT as a heavy metal adsorbent in animal's diets, implying a potential protective role against heavy metal toxicities.

Daily pattern of pituitary glutamine, glutamate, and aspartate content disrupted by cadmium exposure

Cadmium is a neurotoxic heavy metal and is considered endocrine disruptor. In this work, we investigate the effects of cadmium on the 24 h changes of aspartate, glutamate, and glutamine content in the pituitary. Adult male Sprague-Dawley rats were treated with 25 or 50 mg/l of cadmium chloride (CdCl(2)) in the drinking water for 30 days. Metal exposure with the lowest dose induced the disappearance of the nocturnal peak of anterior pituitary amino acid content, and the appearance of a peak of glutamine concentration during the resting phase of the photoperiod. After exposure to 50 mg/l of CdCl(2), the peaks of anterior pituitary amino acid content at 12:00 and 00:00 h disappeared, and two minimal values at these same hours and a peak at 08:00 h appeared. In the posterior pituitary, cadmium treatment with the lowest dose induced the appearance of a peak of aspartate and glutamate concentration at 12:00 h, and the disappearance of the peak of glutamine content at 16:00 h. After exposure to 50 mg/l of CdCl(2) aspartate and glutamate daily pattern presented two maximal values between 00:00 and 04:00 h, and the metal abolished glutamine daily pattern. These results suggest that cadmium disrupted aspartate, glutamate, and glutamine daily pattern in the pituitary.

Effects of cadmium on serum sex hormone levels in pigs

An inhibition of sex hormone secretion is observed in domestic animals exposed to cadmium in experimental conditions. Ninety-six gilts (Duroc x Landrace x Yorkshire, initial weight 27.59 kg) were randomly assigned into four different groups with three replications in each group (eight gilts per replication). The groups received the corn-soybean basal diet and supplemented with 0, 0.5, 5.0 and 10.0 mg/kg cadmium (as CdCl2) respectively. The feeding trial was ended when body weight of pigs was approximately 90 kg. The results showed that 10.0 mg/kg cadmium significantly decreased average daily gain (p < 0.05) and increased feed/gain ratio (p < 0.05) of pigs. Follicle-stimulating hormone, luteinizing hormone, oestradiol (E2) and progesterone levels in serum of the pigs fed the diet supplemented with 10.0 mg/kg cadmium were lower significantly than those of the control (p < 0.05). Compared with the control, no changes were found in the levels mentioned above when the pigs fed the diet supplemented with 0.5 or 5.0 mg/kg cadmium (p > 0.05). The changes of regulatory mechanism of the pituitary-ovary axis may be the result of cadmium accumulation in pituitary and ovary and should be investigated further.

Inhibitory effect of Cd2+ on glycine-induced chloride current in rat hippocampal neurons

The effects of cadmium (Cd(2+)) on glycine-induced Cl(-) current (I(Gly)) were investigated in acutely dissociated rat hippocampal CA1 neurons using the conventional whole-cell patch-clamp technique in this study. We found that Cd(2+) reversibly and concentration-dependently, reduced the amplitudes of I(Gly), with an IC(50) of 1.27 mM and Hill coefficient of 0.45. The depression of I(Gly) by Cd(2+) was independent of membrane voltage between -60 and +40 mV and did not involve a shift in the reversal potential of the current. A non-competitive inhibition was suggested by a double reciprocal plot of the effects of Cd(2+) on the concentration-response curve of the I(Gly). Since intracellular dialysis with 3mM Cd(2+) failed to modify I(Gly), it was suggested that the site of action of Cd(2+) is extracellular. The suppression of I(Gly) by Zn(2+) was unaffected by 3mM Cd(2+), which indicated that Zn(2+) and Cd(2+) bind to independent sites on glycine receptor. The results show that Cd(2+) decreases I(Gly) in acutely dissociated rat hippocampal neurons and the depression of I(Gly) by Cd(2+) may contribute to worsen the neurotoxicological impairment.

Sensorimotor developmental delays and lower anxiety in rats prenatally exposed to cadmium

Pregnant rats were treated with 0.3 or 0.6 mg cadmium (CdCl2) kg(-1) injected subcutaneously on a daily basis from gestational day 7 to day 15 (organogenesis period). One control group was not injected and the other received saline. Offspring were tested for ontogeny of sensorimotor development and at 45 or 90 days of age for anxiety behavior. The study of sensorimotor development showed that gestational exposure to 0.6 mg Cd kg(-1) produced a delay in the development of the righting reflex and of the cliff aversion in the pups. No differences were observed in the development of the negative geotaxis, nor in the ages of eye and ear opening. Anxiety studies using an elevated plus maze showed a lower anxiety in all the offspring prenatally exposed to 0.6 mg Cd kg(-1) as these rats spent more time and entered the open arms more times compared with those of the other groups. The results demonstrate that exposure to low levels of Cd during organogenesis may modify some central nervous system functions.

Developmental exposure to cadmium alters responsiveness to cocaine in the rat

The purpose of the present report was to investigate the potential interactive relation between perinatal (gestation/lactation) cadmium exposure and changes in responsiveness to cocaine. In Experiment 1, adult female rats were exposed to a diet containing 50 ppm cadmium (as cadmium chloride) or a diet containing no added cadmium for 30 days prior to breeding with nonexposed males. The metal-exposure regimen continued throughout gestation, and for 15 days of lactation, at which time all animals were placed on standard rat chow diets containing no added cadmium for the remainder of the investigation. Atomic absorption assays confirmed that cadmium concentrations were significantly elevated in metal-exposed dams, littermates, and test animals. Offspring were weaned on postnatal day (PND) 21 and commenced cocaine sensitization testing on PND 70. Testing operations for controls and animals perinatally exposed to cadmium consisted of 21 daily i.p. injections of vehicle (saline) or 10 mg/kg cocaine HCl, and subsequent recording of locomotor activity. Subsequently, across successive days, all animals received 0, 10, and 20 mg/kg cocaine challenges. The results showed that cocaine sensitization was attenuated in animals perinatally exposed to cadmium. A similar pattern of antagonism was observed in Experiment 2 where a higher dose of cocaine was required to produce conditioned place preference (CPP) in cadmium-exposed animals. The implications of these findings with respect to the interactive role of cadmium in the dynamics of cocaine use/abuse remain unclear.

Study of the activity of several brain enzymes like markers of the neurotoxicity induced by perinatal exposure to lead and/or cadmium

Five enzymes, considered keys to the correct function of the central nervous system (CNS) were chosen to study their utility as markers of the possible neurotoxic effects produced by the perinatal exposure to lead and/or cadmium. With this aim, lead acetate (300 mg/l) and/or cadmium acetate (10 mg/l) were administered to pregnant Wistar rats from day 1 of pregnancy to parturition (day 0) or until weaning (day 21). Brains were used to determine the activity of acid phosphatase (ACP), alkaline phosphatase (ALP), catalase (CAT), acetylcholinesterase (AchE) and ATP-ases (Na(+)/K(+) and Mg(2+)/Ca(2+) dependent). The general decrease of the activity of these enzymes observed after the treatment with heavy metals suggests that lead and cadmium are able to reach the CNS and impair its function by neurochemical changes. On the other hand, the results showed an increase of the activity of CAT; which possibly indicates that lead and cadmium might have other mechanisms of action, such as increasing oxidative damage in the CNS. Finally, the study of the effects produced by the simultaneous administration of lead and cadmium suggests that, in general, both metals exert an additive effect, either competing for the same inhibitory binding sites or increasing cellular damage. In conclusion, the study of the activity of enzymes is revealed as an effective method to measure the neurotoxicity induced by lead and cadmium.

Perinatal exposure to lead and cadmium affects anxiety-like behaviour

The present study examines the effects of early simultaneous exposure to low level of lead and cadmium on anxiety-like behaviour in the rat, and on monoamine levels in the hypothalamus and hippocampus at weaning and adult animals. Rats were intoxicated with cadmium acetate (10 mg/l) and lead acetate (300 mg/l) in drinking water from the beginning of pregnancy until weaning. Maternal co-exposure to lead and cadmium produced mainly alterations in dopaminergic and serotoninergic systems of hippocampus in both age studied, while noradrenaline content in hypothalamus and hippocampus remained unchanged at 75 days of age. The intoxicated rats showed an increased on indices of anxiety on the elevated plus-maze. These long-term changes in anxiety-like behaviour can be related to dopaminergic and serotoninergic alterations detected in hippocampus.

Effects of combined exposure to lead and cadmium on the hypothalamic-pituitary axis function in proestrous rats

The effects of lead and cadmium on the hypothalamic-pituitary axis were studied in proestrous rats. Adult female rats were treated intraperitonially with either lead acetate and cadmium acetate alone or in combination at a dose of 0.05 mg/kg daily for 15 days. Serotonin (5-HT) and norepinephrine (NE) levels decreased in individually and combined metal treated groups whereas dopamine (DA) levels were decreased only in the cadmium-exposed group. The pituitary levels of luteinizing hormone (LH) and follicle stimulating hormone (FSH) were decreased significantly in cadmium and combined treatment groups. In contrast, lead exposure failed to cause any change in serum LH and FSH levels, whereas cadmium and combined treatments showed significant decrease in serum LH and FSH levels as compared with control. The accumulation of both metals increased in the hypothalamus and pituitary after treatment. These data suggest that the metal accumulation disrupts the regulatory mechanisms of the hypothalamic-pituitary axis where the effects produced by the combined treatment of metals are not additive.

Pb and Cd poisoning during development alters cerebellar and striatal function in rats

The present study was designed to examine more fully the neurochemical and behavioral interactions that derive from continued lead and cadmium poisoning in pups, whose mothers were exposed via drinking water (300 mg/l of Pb and 10 mg/l of Cd) throughout pregnancy and lactation. At weaning, these metals produced an increase in DOPAC, 5-HT and 5-HIAA contents in cerebellum, but the monoamine contents in striatum remained unaltered. The cerebral energetic metabolism was modified by the Cd-Pb exposition only in striatum. On the other hand, the Na+/K+-ATPase activity was inhibited significantly in both regions at PN21, whereas the alkaline phosphatase activity was not affected by the treatment. The intoxicated animals showed a short-term normocitic anemia, but revealed long-term alterations in the motor activity in open-field, where they showed an increase in both ambulating and rearing. So, it can be concluded that perinatal exposure to lead and cadmium provoke neurochemical alterations in cerebellum and striatum that can be related with the changes in motor activity observed in the adulthood.

Oral cadmium exposure throughout puberty does not inhibit secretion of prolactin, GH and ACTH through dopamine metabolism changes in male rat

This work analyzed possible dopamine-mediated cadmium effects on plasma prolactin, GH and ACTH levels and if these changes were related to metal accumulation. Male rats were treated from day 30 to 60 of life with 50 mg/L of CdCl2 in the drinking water. Cadmium exposure decreased the dopamine (DA) metabolism (DOPAC/DA ratio) in all brain areas studied, and plasma levels of prolactin, GH and ACTH were diminished. The cadmium concentration did not increase nor in hypothalamus nor in the pituitary after the metal exposure. These results suggest that cadmium inhibits the secretion of these pituitary hormones and this inhibitory effect is not mediated by dopamine or the degree of metal accumulation.

Exposure of cadmium from infant formulas and weaning foods

Cadmium levels were determined in 59 baby food samples, including milk-based, cereal and milk-based and soy-based formulas, recommended from 0 to 18 months of age. Determinations were performed by Zeeman graphite furnace atomic absorption spectrophotometry, after dry ashing, with parallel determinations of certified reference samples. Mean cadmium levels were found to range from 1.10 to 23.5 micrograms/kg fresh weight concentrated formulas. Levels were related to the composition of the diets. Formulas based on cow's milk had the lowest concentrations. Soy formulas contained approximately six times more cadmium than cow's milk formulas, and diets with a cereal content had 4-21 times higher mean levels. The mean weekly intakes of dietary cadmium were estimated to vary between 0.10 and 3.05 micrograms/kg body weight of the child, if the recommended amount of formula were to be consumed at the recommended age, and if the child were of average weight. This estimation however does not include the contribution of cadmium from drinking water. The highest intake on a body weight basis was found in 6-month-old children, consuming the recommended amount of wheat-, oat- and milk-based formulas. This intake is below the provisional tolerable weekly intake (PTWI) of 7 micrograms/kg body weight, established by a WHO/FAO expert group. However, the risk assessment is based on renal effects in adults. Furthermore, preparations of a formula by adding water with cadmium concentrations at the WHO guideline level could lead to intakes at the PTWI level. Compared to breast-fed children, the exposure of dietary cadmium from weaning diets can be up to 12 times higher in children fed infant formula.

Neurochemical changes in newborn rat's brain after gestational cadmium and lead exposure

Gestational administration of cadmium (10 mg/l) and lead (300 mg/l) produced a strong decrease in proteins at birth (-17%) and on day 5 (-31%) as well as in brain lipid amount on both days (-11 and -23%, respectively). At day 5 postnatal the exposure also produced a marked decrease in DNA and RNA concentrations with respect to the control group. On the other hand, we found a significant increase of indoleamine content in all brain areas studied in the cadmium-lead group and so the dopamine and its metabolite in mesencephalon, whereas dopamine levels in metencephalon decreased significantly. This data suggests that gestational and early lactational exposure to low dose of cadmium and lead could produce alterations in monoaminergic metabolism that can place the exposed animal to a significant risk in adulthood.