Effect of latent iron deficiency on metal levels of rat brain regions

Iron: Not Just a Passive Bystander in AITD

Autoimmune thyroid disease (AITD) is the most prevalent autoimmune disease all over the world and the most frequent cause of hypothyroidism in areas of iodine sufficiency. The pathogenesis of AITD is multifactorial and depends on complex interactions between genetic and environmental factors, with epigenetics being the crucial link. Iron deficiency (ID) can reduce the activities of thyroid peroxidase and 5′-deiodinase, inhibit binding of triiodothyronine to its nuclear receptor, and cause slower utilization of T3 from the serum pool. Moreover, ID can disturb the functioning of the immune system, increasing the risk of autoimmune disorders. ID can be responsible for residual symptoms that may persist in patients with AITD, even if their thyrometabolic status has been controlled. The human lifestyle in the 21st century is inevitably associated with exposure to chemical compounds, pathogens, and stress, which implies an increased risk of autoimmune disorders and thyroid dysfunction. To summarize, in our paper we discuss how iron deficiency can impair the functions of the immune system, cause epigenetic changes in human DNA, and potentiate tissue damage by chemicals acting as thyroid disruptors.

The effect of maternal iron deficiency on zinc and copper levels and on genes of zinc and copper metabolism during pregnancy in the rat

Fe deficiency is relatively common in pregnancy and has both short- and long-term consequences. However, little is known about the effect on the metabolism of other micronutrients. A total of fifty-four female rats were fed control (50 mg Fe/kg) or Fe-deficient diets (7·5 mg/kg) before and during pregnancy. Maternal liver, placenta and fetal liver were collected at day 21 of pregnancy for Cu and Zn analysis and to measure expression of the major genes of Cu and Zn metabolism. Cu levels increased in the maternal liver (P=0·002) and placenta (P=0·018) of Fe-deficient rats. Zn increased (P<0·0001) and Cu decreased (P=0·006) in the fetal liver. Hepatic expression of the Cu chaperones antioxidant 1 Cu chaperone (P=0·042) and cytochrome c oxidase Cu chaperone (COX17, P=0·020) decreased in the Fe-deficient dams, while the expression of the genes of Zn metabolism was unaltered. In the placenta, Fe deficiency reduced the expression of the chaperone for superoxide dismutase 1, Cu chaperone for superoxide dismutase (P=0·030), ceruloplasmin (P=0·042) and Zn transport genes, ZRT/IRT-like protein 4 (ZIP4, P=0·047) and Zn transporter 1 (ZnT1, P=0·012). In fetal liver, Fe deficiency increased COX17 (P=0·020), ZRT/IRT-like protein 14 (P=0·036) and ZnT1 (P=0·0003) and decreased ZIP4 (P=0·004). The results demonstrate that Fe deficiency during pregnancy has opposite effects on Cu and Zn levels in the fetal liver. This may, in turn, alter metabolism of these nutrients, with consequences for development in the fetus and the neonate.

Study on Impact of Iron and Folic Acid on the Plasma Trace Minerals in Pregnant Anemic Women

Iron deficiency anemia is one of the causes that lead to significant mortality and morbidity among pregnant women and fetus. The present study was undertaken to explore oral iron supplementation can modify the metal contents in pregnant anemic women. Iron and folic acid supplementations was given to 500 anemic women (mild = 200, moderate = 200, and severe = 100) and 100 age matched non-anemic controls daily for 100 days. Blood index values and plasma trace minerals were estimated as per standard protocols. Haemoglobin and ferritin levels were found significantly increased (p < 0.001) in anemic and control subjects after treatment. Moreover, the serum transferring receptor levels and total iron binding capacity were found significantly decreased in all treated groups. Iron (Fe), zinc (Zn) and copper (Cu) levels were found increased (p < 0.01) after oral iron supplementation groups. Moreover, selenium (Se) manganese (Mn) and were found to be decreased in all treated groups. Data provides the conclusion that iron and folic acid supplementation recovered the essential trace minerals, except manganese, which may lead to various complications including peroxidation of vital body molecules resulting in increased risk for pregnant women as well as fetus.

Regulation of trace elements and redox status in striatum of adult rats by long-term aerobic exercise depends on iron uptakes

We investigated the effects of aerobic exercise (AE) on trace element contents and redox status in the striatum of rats with different diet iron. Weaned female rats were randomly fed with iron-adequate diet (IAD), iron-deficient diet (IDD), and iron-overloaded diet (IOD). After feeding their respective diet for 1 month, the rats fed with same diet were divided into swimming and maintaining sedentary (S) group. After 3 months, the non-heme iron (NHI), Mn, Cu, and Zn in the striatum were measured. Meanwhile, malonaldehyde acid (MDA), total superoxide dismutase activity, hydroxyl radical scavenging activity, and total antioxidant capacity were also analyzed. As compared with respective S rats, Mn, Cu, and Zn contents were significantly decreased in IDDE, but no significantly changes could be seen in IADE or IODE. A negative correlation of NHI with Cu contents in IDDE and positive correlations of NHI with Cu, or Zn contents in IADE, or with Mn or Cu contents in IODE were observed. In addition, striatum MDA was significantly decreased and anti-oxidative variables were increased in IODE compared to IODS. Our results suggest that the modification of trace elements and redox status in the striatum of rats caused by AE depends on dietary iron contents and that AE may also regulate the metabolic relationship of iron storage with other trace elements.

Iron, hepcidin, and the metal connection

Identification of new players in iron metabolism, such as hepcidin, which regulates ferroportin and divalent metal transporter 1 expression, has improved our knowledge of iron metabolism and iron-related diseases. However, from both experimental data and clinical findings, "iron-related proteins" appear to also be involved in the metabolism of other metals, especially divalent cations. Reports have demonstrated that some metals may affect, directly or indirectly, the expression of proteins involved in iron metabolism. Throughout their lives, individuals are exposed to various metals during personal and/or occupational activities. Therefore, better knowledge of the connections between iron and other metals could improve our understanding of iron-related diseases, especially the variability in phenotypic expression, as well as a variety of diseases in which iron metabolism is secondarily affected. Controlling the metabolism of other metals could represent a promising innovative therapeutic approach.

Functional roles of transferrin in the brain

BACKGROUND

Transferrin is synthesized in the brain by choroid plexus and oligodendrocytes, but only that in the choroid plexus is secreted. Transferrin is a major iron delivery protein to the brain, but the amount transcytosed across the brain microvasculature is minimal. Transferrin is the major source of iron delivery to neurons. It may deliver iron to immature oligodendrocytes but this trophic effect declines over time while iron requirements for maintaining myelination continue. Finally, transferrin may play an important role in neurodegenerative diseases through its ability to mobilize iron.

SCOPE OF REVIEW

The role of transferrin in maintaining brain iron homeostasis and the mechanism by which it enters the brain and delivers iron will be discussed. Its relevance to neurological disorders will also be addressed.

MAJOR CONCLUSIONS

Transferrin is the major iron delivery protein for neurons and the microvasculature, but has a limited role for glial cells. The main source of transferrin in the brain is likely from the choroid plexus although the concentration of transferrin at any given time in the brain includes that synthesized in oligodendrocytes. Little is known about brain iron egress or the role of transferrin in this process.

GENERAL SIGNIFICANCE

Neuron survival requires iron, which is predominantly delivered by transferrin. The concentration of transferrin in the cerebrospinal fluid is reflective of brain iron availability and can function as a biomarker in disease. Accumulation of iron in the brain contributes to neurodegenerative processes, thus an understanding of the role that transferrin plays in regulating brain iron homeostasis is essential. This article is part of a Special Issue entitled Transferrins: Molecular mechanisms of iron transport and disorders.

Brain iron deficiency and excess; cognitive impairment and neurodegeneration with involvement of striatum and hippocampus

While iron deficiency is not perceived as a life threatening disorder, it is the most prevalent nutritional abnormality in the world, and a better understanding of modes and sites of action, can help devise better treatment programs for those who suffer from it. Nowhere is this more important than in infants and children that make up the bulk of iron deficiency in society. Although the effects of iron deficiency have been extensively studied in systemic organs, until very recently little attention was paid to its effects on brain function. The studies of Oski at Johns Hopkin Medical School in 1974, demonstrating the impairment of learning in young school children with iron deficiency, prompted us to study its relevance to brain biochemistry and function in an animal model of iron deficiency. Indeed, rats made iron deficient have lowered brain iron and impaired behaviours including learning. This can become irreversible especially in newborns, even after long-term iron supplementation. We have shown that in this condition it is the brain striatal dopaminergic-opiate system which becomes defective, resulting in alterations in circadian behaviours, cognitive impairment and neurochemical changes closely associated with them. More recently we have extended these studies and have established that cognitive impairment may be closely associated with neuroanatomical damage and zinc metabolism in the hippocampus due to iron deficiency, and which may result from abnormal cholinergic function. The hippocampus is the focus of many studies today, since this brain structure has high zinc concentration and is highly involved in many forms of cognitive deficits as a consequence of cholinergic deficiency and has achieved prominence because of dementia in ageing and Alzheimer's disease. Thus, it is now apparent that cognitive impairment may not be attributed to a single neurotransmitter, but rather, alterations and interactions of several systems in different brain regions. In animal models of iron deficiency it is apparent that dopaminergic interaction with the opiate system and cholinergic neurotransmission may be defective.

Neurotoxicity of inhaled manganese: public health danger in the shower?

CONTEXT

Manganese (Mn) is an essential trace element but is neurotoxic at high doses. Showering with Mn-laden water has never been evaluated as a central nervous system (CNS) delivery vector for Mn, even though intranasally administered Mn in laboratory animals circumvents the blood-brain barrier and passes directly into the brain via olfactory pathways.

OBJECTIVE

To review the literature on Mn and attempt to quantify potential human CNS exposure to manganese from showering.

DATA SOURCES

We systematically searched Medline 11/9/02 and again on 3/9/04. The following search terms were used: manganese, water, drinking water, shower, showering, bath, bathing and inhalation, then combined with "water or drinking water or showering or shower or bathing or inhalation."

STUDY SELECTION

Animal experimental investigations, human epidemiological studies, and consensus and governmental reports were utilized.

DATA EXTRACTION

Data were extracted by both authors and extrapolations to humans were calculated by one of us (JGS) controlling for age, length of exposure and known respiratory differences between rats and humans.

DATA SYNTHESIS

During a decade of showering in Mn-contaminated water, models for children and adults show higher doses of aerosolized Mn (3-fold and 112-fold greater, respectively) than doses reported to cause Mn brain deposition in rats.

CONCLUSIONS

Long-term shower exposure to Mn-laden water may pose a significant risk for CNS neurotoxicity via olfactory uptake in up to 8.7 million Americans. If our results are confirmed, regulatory agencies must rethink existing Mn drinking water standards.

The influence of high iron diet on rat lung manganese absorption

Individuals chronically exposed to manganese are at high risk for neurotoxic effects of this metal. A primary route of exposure is through respiration, although little is known about pulmonary uptake of metals or factors that modify this process. High dietary iron levels inversely affect intestinal uptake of manganese, and a major goal of this study was to determine if dietary iron loading could increase lung non-heme iron levels and alter manganese absorption. Rats were fed a high iron (1% carbonyl iron) or control diet for 4 weeks. Lung non-heme iron levels increased approximately 2-fold in rats fed the high iron diet. To determine if iron-loading affected manganese uptake, 54Mn was administered by intratracheal (it) instillation or intravenous (iv) injection for pharmacokinetic studies. 54Mn absorption from the lungs to the blood was lower in it-instilled rats fed the 1% carbonyl iron diet. Pharmacokinetics of iv-injected 54Mn revealed that the isotope was cleared more rapidly from the blood of iron-loaded rats. In situ analysis of divalent metal transporter-1 (DMT1) expression in lung detected mRNA in airway epithelium and bronchus-associated lymphatic tissue (BALT). Staining of the latter was significantly reduced in rats fed the high iron diet. In situ analysis of transferrin receptor (TfR) mRNA showed staining in BALT alone. These data demonstrate that manganese absorption from the lungs to the blood can be modified by iron status and the route of administration.

Manganese dosimetry: species differences and implications for neurotoxicity

Manganese (Mn) is an essential mineral that is found at low levels in food, water, and the air. Under certain high-dose exposure conditions, elevations in tissue manganese levels can occur. Excessive manganese accumulation can result in adverse neurological, reproductive, and respiratory effects in both laboratory animals and humans. In humans, manganese-induced neurotoxicity (manganism) is the overriding concern since affected individuals develop a motor dysfunction syndrome that is recognized as a form of parkinsonism. This review primarily focuses on the essentiality and toxicity of manganese and considers contemporary studies evaluating manganese dosimetry and its transport across the blood-brain barrier, and its distribution within the central nervous system (CNS). These studies have dramatically improved our understanding of the health risks posed by manganese by determining exposure conditions that lead to increased concentrations of this metal within the CNS and other target organs. Most individuals are exposed to manganese by the oral and inhalation routes of exposure; however, parenteral injection and other routes of exposure are important. Interactions between manganese and iron and other divalent elements occur and impact the toxicokinetics of manganese, especially following oral exposure. The oxidation state and solubility of manganese also influence the absorption, distribution, metabolism, and elimination of manganese. Manganese disposition is influenced by the route of exposure. Rodent inhalation studies have shown that manganese deposited within the nose can undergo direct transport to the brain along the olfactory nerve. Species differences in manganese toxicokinetics and response are recognized with nonhuman primates replicating CNS effects observed in humans while rodents do not. Potentially susceptible populations, such as fetuses, neonates, individuals with compromised hepatic function, individuals with suboptimal manganese or iron intake, and those with other medical states (e.g., pre-parkinsonian state, aging), may have altered manganese metabolism and could be at greater risk for manganese toxicity.

Fetal iron deficiency disrupts the maturation of synaptic function and efficacy in area CA1 of the developing rat hippocampus

Late fetal and early postnatal iron deficiency (ID) is a common condition that causes learning and memory impairments in humans while they are iron deficient and following iron repletion. Rodent models of fetal ID demonstrate significant short- and long-term hippocampal structural and biochemical abnormalities that may predispose hippocampal area CA1 to abnormal electrophysiology. Rat pups made iron deficient during the fetal and early postnatal period were assessed for basal synaptic transmission, paired-pulse facilitation (PPF), and long-term potentiation (LTP) in CA1 at postnatal days (P)15 and P30 while iron deficient and at P65 following iron repletion. Our results showed no differences in basal synaptic transmission between iron sufficient and iron deficient pups at P15 or P30, but the ID group did fail to demonstrate the expected developmental increase in synaptic strength by P65 (P < 0.05). Similarly, PPF ratios from iron deficient slices also failed to demonstrate the characteristic developmental changes seen in the iron sufficient group (P < 0.001). Iron deficient slices retained a developmentally immature P15 pattern of LTP expression at P30 and after iron repletion, and LTP expression was lower (P < 0.05) in the iron deficient group at P65. Thus, ID in the fetal and early postnatal period delays or abolishes the developmental maturation of electrophysiological components of synaptic efficacy and plasticity, resulting in abnormalities beyond the period of deficiency. These findings provide a functional corroboration to previous structural and biochemical abnormalities found in the iron deficient rat hippocampus and provide a potential model for learning and memory deficits seen in humans exposed to fetal and early postnatal ID.

Globus pallidus: a target brain region for divalent metal accumulation associated with dietary iron deficiency

Recently, iron deficiency has been connected with a heterogeneous accumulation of manganese in the rat brain. The striatum is particularly vulnerable, for there is a significant negative correlation between accumulated manganese and gamma-aminobutyric acid levels. The effect of dietary iron deficiency on the distribution of zinc and copper, two other divalent metals with essential neurobiological roles, is relatively unexplored. Thus, the primary goal of this study was to examine the effect of manipulating dietary iron and manganese levels on the concentrations of copper, iron, manganese and zinc in five rat brain regions as determined with inductively coupled plasma mass spectrometry analysis. Because divalent metal transporter has been implicated as a transporter of brain iron, manganese, and to a lesser extent zinc and copper, another goal of the study was to measure brain regional changes in transporter levels using Western blot analysis. As expected, there was a significant effect of iron deficiency (P < 0.05) on decreasing iron concentrations in the cerebellum and caudate putamen; and increasing manganese concentrations in caudate putamen, globus pallidus and substantia nigra. Furthermore, there was a significant effect of iron deficiency (P < 0.05) on increasing zinc concentration and a statistical trend (P = 0.08) toward iron deficiency-induced copper accumulation in the globus pallidus. Transporter protein in all five regions increased due to iron deficiency compared to control levels (P < 0.05); however, the globus pallidus and substantia nigra revealed the greatest increase. Therefore, the globus pallidus appears to be a target for divalent metal accumulation that is associated with dietary iron deficiency, potentially caused by increased transporter protein levels.

Manganese neurotoxicity

Manganese is an essential trace element and it is required for many ubiquitous enzymatic reactions. While manganese deficiency rarely occurs in humans, manganese toxicity is known to occur in certain occupational settings through inhalation of manganese-containing dust. The brain is particularly susceptible to this excess manganese, and accumulation there can cause a neurodegenerative disorder known as manganism. Characteristics of this disease are described as Parkinson-like symptoms. The similarities between the two disorders can be partially explained by the fact that the basal ganglia accumulate most of the excess manganese compared with other brain regions in manganism, and dysfunction in the basal ganglia is also the etiology of Parkinson's disease. It has been proposed that populations already at heightened risk for neurodegeneration may also be more susceptible to manganese neurotoxicity, which highlights the importance of investigating the human health effects of using the controversial compound, methylcyclopentadienyl manganese tricarbonyl (MMT), in gasoline to increase octane. The mechanisms by which increased manganese levels can cause neuronal dysfunction and death are yet to be elucidated. However, oxidative stress generated through mitochondrial perturbation may be a key event in the demise of the affected central nervous system cells. Our studies with primary astrocyte cultures have revealed that they are a critical component in the battery of defenses against manganese-induced neurotoxicity. Additionally, evidence for the role of oxidative stress in the progression of manganism is reviewed here.

Inhaled iron, unlike manganese, is not transported to the rat brain via the olfactory pathway

Iron and manganese share structural, biochemical, and physiological similarities. The objective of this study was to determine whether iron, like manganese, is transported to the rat brain via the olfactory tract following inhalation exposure. Eight-week-old male CD rats were exposed to approximately 0.31 mg Fe per m(3) (mass median aerodynamic diameter = 2.99 microm; geometric standard deviation = 1.15) via inhalation for a target duration of 90 min. Following exposure, rats were euthanized immediately (0) or at 1, 2, 4, 8, or 21 days postexposure. In addition to nasal and regional brain tissues, blood, and viscera were also collected. 59Fe concentrations were determined by gamma spectrometry. Further, heads were collected and frozen, and autoradiograms were prepared to visualize the location of 59Fe from the nose to the brain. Finally, olfactory mucosa samples collected at 0, 2, 4, and 21 days postexposure were further analyzed using high-performance liquid chromatography (HPLC) plus gamma spectroscopy to determine the association between 59Fe and transferrin. Data obtained from gamma spectrometry revealed that most of the iron remained in the nasal regions of the olfactory system and that less than 4% of iron deposited on the olfactory mucosa was observed in the olfactory bulb. Autoradiograms confirmed the data obtained from gamma spectrometry. 59Fe activity was absent in the olfactory regions of the brain even 4 days postexposure. Further, HPLC-gamma spectroscopy analyses indicated that 59Fe in the olfactory mucosa was coeluted with transferrin. Hence iron, unlike manganese, is not readily transported to the brain via the olfactory tract.

Effect of latent iron deficiency on GABA and glutamate neuroreceptors in rat brain

Eight weeks of latent iron deficiency in weaned female rats of Sprague Dawley strain maintained on experimental low-iron diet (18-20 mg/kg) did not significantly change the gross body, weight and tissue weights of brain and liver. Packed cell volume (PCV) and hemoglobin concentration remained unaltered. However, non-heme iron content in liver and brain decreased significantly (p<0.001). The activities of glutamate dehydrogenase, glutamic acid decarboxylase, and GABA-transaminase (GABA-T) in brain decreased by 15%, 11.4% and 25.7% respectively. However, this decrease was not statistically significant. Binding of(3)H Muscimol at pH 7.5 and 1 mg protein/assay increased by 143% (p<0.001) in synaptic vesicular membranes from iron-deficient rats as compared to the controls.(3)H glutamate binding to the synaptic vesicles was also carried out under similar condition. However, the L-glutamate binding was reduced by 63% in the vesicular membranes of iron deficient animals. These studies indicate that iron plays important functional role in both excitatory and inhibitory neurotransmitter receptors.

Non-anemic iron depletion, oral iron supplementation and indices of copper status in college-aged females

OBJECTIVES

Indices of copper status, specifically serum copper and ceruloplasmin concentrations and erythrocyte superoxide dismutase activity, and iron status, including serum ferritin, transferrin receptors, hemoglobin and hematocrit, were studied in 27 college-aged females with adequate iron versus low iron stores.

METHODS

Serum copper and ceruloplasmin concentrations, erythrocyte superoxide dismutase activity, serum ferritin, transferrin receptors, hemoglobin and hematocrit were studied in 15 females with non-anemic iron depletion before and after five weeks of iron supplementation and in 12 healthy iron-adequate females aged 19 to 28 years.

RESULTS

Mean hemoglobin, hematocrit and ferritin concentrations of the control group (144 +/- 11 g/L, 43 +/- 3% and 38 +/- 15 micro g/L, respectively) were significantly higher than those of the iron depleted group prior to supplementation (134 +/- 9 g/L, 39 +/- 2% and 11 +/- 6 micro g/L, respectively). The serum transferrin receptor to serum ferritin ratio was significantly greater for the iron depleted group prior to supplementation (890 +/- 753) versus the control group (151 +/- 61). Mean serum copper and ceruloplasmin concentrations and erythrocyte superoxide dismutase activity of the iron-adequate control group (20.0 +/- 5.7 micro mol/L, 463 +/- 142 mg/L and 527 +/- 124 U/mL, respectively) were significantly higher than those of the iron depleted group (12.4 +/- 3.8 micro mol/L, 350 +/- 108 mg/L and 353 +/- 186 U/mL, respectively) prior to supplementation. Following iron supplementation, hematocrit and ferritin concentrations of the iron depleted group significantly increased to 42 +/- 3% and 26 +/- 8 micro g/L, respectively. Mean serum transferrin receptor concentrations and the serum transferrin receptor to ferritin ratios significantly decreased in the iron depleted group following supplementation (6.1 +/- 1.6 mg/L to 4.6 +/- 1.5 mg/L and 890 +/- 753 to 198 +/- 114, respectively). Iron supplementation also significantly increased the mean serum copper concentration to 14.2 +/- 5.4 micro mol/L and, in subjects with serum ferritin concentrations </=12 micro g/L, the mean serum ceruloplasmin concentration.

CONCLUSIONS

Non-anemic iron depletion characterized by low iron stores is associated with negative impacts on copper status. Iron supplements improved indices of iron status and serum copper and ceruloplasmin concentrations. Whether the diminished serum copper and ceruloplasmin concentrations and superoxide dismutase activity are associated with free radical damage to iron depleted cells requires further investigation.

Effect of latent iron deficiency on gaba and glutamate neuroreceptors in rat brain

Eight weeks of latent iron deficiency in weaned female rats of Sprague Dawley strain maintained on experimental low-iron diet (18-20 mg/Kg) did not significantly change the gross body weight and tissue weights of brain and liver. Packed cell volume (PCV) and hemoglobin concentration remained unaltered. However, non-heme iron content in liver and brain decreased significantly (P<0.001). The activities of glutamate dehydrogenase, glutamic acid decarboxylase, and GABA-transaminase (GABA-T) in brain decreased by 15%, 11.4% and 25.7% respectively. However, this decrease was not statistically significant. Binding of(3)H Muscimol at pH 7.5 and 1 mg protein/assay increased by 143% (P<0.001) in synaptic vesicular membranes from iron-deficient rats as compared to the controls.(3)H glutamate binding to the synaptic vesicles was also carried out under similar condition. However, the L-glutamate binding was reduced by 63% in the vesicular membranes of iron deficient animals. These studies in dicate that iron plays an important functional role in both excitatory and inhibitory neurotransmitter receptors.

Transferrin is required for normal distribution of 59Fe and 54Mn in mouse brain

Hypotransferrinemia (hpx/hpx) is a genetic defect in mice resulting in <1% of normal plasma transferrin (Tf) concentrations; heterozygotes for this mutation (+/hpx) have low circulating Tf concentrations. These mice provide a unique opportunity to examine the role of Tf in Fe and Mn transport in the brain. Twenty weanling wild-type BALB/cJ mice, 15 +/hpx mice, and 12 hpx/hpx mice of both sexes were injected i.v. with either 54MnCl(2) or 59FeCl(3) either 1 h or 1 week before killing at 12 weeks of age. Total brain counts of 54Mn and 59Fe were measured, and regional brain distributions were assessed by autoradiography. Hypotransferrinemia did not affect total brain Mn uptake. However, 1 week after i.v. injection, hpx/hpx mice had less 54Mn in forebrain structures including cerebral cortex, corpus callosum, striatum, and substantia nigra. The +/hpx mice had the highest total brain 59Fe accumulation 1 h after i.v. injection. A striking effect of regional distribution of 59Fe was noted 1 week after injection; in hpx/hpx mice, 59Fe was located primarily in choroid plexus, whereas in +/+ and +/hpx mice 59Fe was widely distributed, with relatively high amounts in cerebral cortex and cerebellum. We interpret these data to mean that Tf is necessary for the transport of Fe but not Mn across the blood-brain barrier, and that there is a Tf-independent uptake mechanism for iron in the choroid plexus. Additionally, these data suggest that endogenous synthesis of Tf is necessary for Fe transport from the choroid plexus.

Behavioral consequences of marginal iron deficiency during development in a murine model

Marginal iron deficiency is a common nutritional disorder in human populations world-wide; however, the neurobehavioral effects of chronic marginal iron (Fe) intakes during development are poorly characterized in animals. For this reason, we investigated whether mice reared on marginal Fe diets during pre- and postnatal development would experience neurobehavioral deficits. Swiss-Webster mice reared on either control (75 ppm Fe) or marginal iron (12.5 ppm) diets were assessed for changes in behavior on postnatal days 30, 40, and 50 using a neurobehavioral test battery. Because alterations in tissue mineral status can lead to an oxidative stress, markers of both protein (glutamine synthetase) and lipid oxidation (TBARS) were measured. Marginal iron animals exhibited a 20-55% reduction in grip strength. Although both marginal iron males and females demonstrated persistent lowering of body weights, statistical analysis using weight as the covariate demonstrated that the grip strength reductions were independent of body weight changes. This reduction in grip strength occurred in conjunction with a 25-45% lowering of brain iron in the marginal iron animals. Despite dramatic reductions in both brain and liver iron, hematocrits were unaffected by dietary iron reductions. Oxidative stress was indicated by an elevation in noniron-stimulated TBARS in the cerebellum of marginal iron animals. These data suggest that a chronic marginal Fe deficiency during critical periods of growth can result in functional changes in motor development even in the absence of iron deficiency anemia; furthermore, alterations in mineral status and oxidative stress may be mechanisms contributing to these observed changes.

Effects of iron deficiency and iron overload on manganese uptake and deposition in the brain and other organs of the rat

Manganese (Mn) is an essential trace element at low concentrations, but at higher concentrations is neurotoxic. It has several chemical and biochemical properties similar to iron (Fe), and there is evidence of metabolic interaction between the two metals, particularly at the level of absorption from the intestine. The aim of this investigation was to determine whether Mn and Fe interact during the processes involved in uptake from the plasma by the brain and other organs of the rat. Dams were fed control (70 mg Fe/kg), Fe-deficient (5-10 mg Fe/kg), or Fe-loaded (20 g carbonyl Fe/kg) diets, with or without Mn-loaded drinking water (2 g Mn/L), from day 18-19 of pregnancy, and, after weaning the young rats, were continued on the same dietary regimens. Measurements of brain, liver, and kidney Mn and nonheme Fe levels, and the uptake of 54Mn and 59Fe from the plasma by these organs and the femurs, were made when the rats were aged 15 and 63 d. Organ nonheme Fe levels were much higher than Mn levels, and in the liver and kidney increased much more with Fe loading than did Mn levels with Mn loading. However, in the brain the increases were greater for Mn. Both Fe depletion and loading led to increased brain Mn concentrations in the 15-d/rats, while Fe loading also had this effect at 63 d. Mn loading did not have significant effects on the nonheme Fe concentrations. 54Mn, injected as MnCl2 mixed with serum, was cleared more rapidly from the circulation than was 59Fe, injected in the form of diferric transferrin. In the 15-d-rats, the uptake of 54Mn by brain, liver, kidneys, and femurs was increased by Fe loading, but this was not seen in the 63-d rats. Mn supplementation led to increased 59Fe uptake by the brain, liver, and kidneys of the rats fed the control and Fe-deficient diets, but not in the Fe-loaded rats. It is concluded that Mn and Fe interact during transfer from the plasma to the brain and other organs and that this interaction is synergistic rather than competitive in nature. Hence, excessive intake of Fe plus Mn may accentuate the risk of tissue damage caused by one metal alone, particularly in the brain.

Influence of iron deficiency and lead treatment on behavior and cerebellar and hippocampal polyamine levels in neonatal rats

Effect of lead exposure and iron-deficiency on polyamine levels in neuronal and glial cells of cerebellum and hippocampus was investigated in weaned rats. Lactating dams with one day old litters were given 0.2% (w/v) lead acetate in drinking water from postnatal day one to twenty one and maintained on an iron-deficient diet. There was an overall reduction of putrescine, spermidine and spermine in neuronal and glial cells of cerebellum and hippocampus consequent to lead exposure and iron-deficiency alone. Lead exposure and iron-deficiency together did not potentiate the polyamine levels in neuronal and glial cells of cerebellum and hippocampus uniformly. However, the enhanced lowering of putrescine in the hippocampal glia, spermidine in cerebellar neuronal and spermine in both neuronal and glial cells of cerebellum during the critical stage of brain development may result in stunted neuronal growth and sprouting in lead exposed and iron-deficient animals. The behavioral alterations as observed in the present study may be due to impaired neuronal development resulting from a depressed polyamine pathway and which could be attributed to cognitive deficits in growing children.

Determination of nonheme iron using inductively coupled plasma-atomic emission spectrometry

A technique for the rapid and accurate estimation of nonheme iron using inductively coupled plasma-atomic emission spectrometry is described. Yttrium was used as an internal standard. An external calibration method was used. The standards were prepared in a matrix composed of 2.5N HCl in 10% (w/v) trichloroacetic acid. The supernatant and coagulum fractions of liver nonheme iron were separated by the method of Drysdale and Ramsay with minor modification. The data determined by this procedure was compared and found to be agreement with data determined by the method of Hallgren. To evaluate the iron status of rats, hemoglobin and liver nonheme iron were determined. Hemoglobin and all of the nonheme iron fractions of the rats fed an iron-deficient diet were significantly lower than those of the rats fed an iron-sufficient diet. The blood content in the liver was estimated to be 80 microL/g from the blood iron concentration, and the difference between total and nonheme iron concentration in liver.