Evaluation of the potential immunotoxicity of chlorinated drinking water in mice

Recent epidemiological studies have reported associations between the consumption of chlorinated drinking water and various types of human cancer; in addition, exposure to chlorine (Cl⁻) in drinking water has been reported to suppress certain immune functions in laboratory animals. The current studies were conducted to extend our knowledge of the effects of drinking water exposure to Cl⁻. Female C57BL/6 mice were administered hyperchlorinated drinking water (7.5, 15, or 30 ppm Cl⁻) for 2 weeks prior to sacrifice for evaluation of spleen and thymus weights, the plaque-forming cell (PFC) response, hemagglutination (HA) titer, and lymphocyte proliferation (LP). Significant reductions in organ weights and immune response were observed in the positive control groups (i.e. dexamethasone- or cyclophosphamide-exposed mice). No consistent differences were observed between the Cl⁻-exposed animals and vehicle control mice for the evaluated parameters. Thus, under the conditions of these experiments, 2 weeks of exposure to hyperchlorinated drinking water had no apparent adverse effects on immune function.     

Persistent effect of in utero meso-2,3-dimercaptosuccinic acid (DMSA) on immune function and lead-induced immunotoxicity

Meso-2,3-dimercaptosuccinic acid (DMSA) is a drug currently employed for cheltion therapy in lead poisoning; however, little is known about its potential effects on the immune system. To examine the effect of DMSA and its capacity to reverse immunotoxicity resulting from exposure to lead in utero, female Fischer 344 rats were administered lead acetate in drinking water from 2 weeks prior to mating until parturition; DMSA was given by gavage on days 6-21 of gestation. The immune function of the female offspring was tested at 13 weeks of age. The results showed that lead (250 ppm) suppressed Th1-type responses (delayed-type hypersensitivity (DTH), interferon gamma (IFN gamma) production), enhanced a Th2-type response (interleukin-4 (IL-4) production), and increased tumor necrosis factor alpha (TNF alpha) production from macrophages. DMSA treatment (60 mg/kg per day) during pregnancy significantly lowered the blood lead levels of both the embryos and the lactating dams as well as the milk lead level of lactating dams. The chelation treatment also reversed the lead-induced alterations in pup body weight, relative spleen weight, TNF alpha, and IL-4 production. But in utero exposure to DMSA alone resulted in decreased DTH response in adult offspring. This was likely due to a reduced cell recruitment, since plasma monocyte chemoattractant protein-1 (MCP-1) levels were decreased. The DMSA-exposed offspring also demonstrated increased interleukin-2 (IL-2) production. These results suggest that DMSA reverses some of the lead-induced immunotoxicity; however, this treatment itself during embryonic development produces subsequent adult immunomodulation.     

Influence of the Oral Administration of Excess Copper on the Immune Response

We have studied the influence of the oral administration ofexcess copper (Cu) on the immune response. With this aim, micemaintained on standard laboratory diet received 50, 100, 200,or 300 ppm of Cu as copper sulfate in the drinking water during3 to 10 weeks. Inhibition of the proliferative response to concanavalinA was observed in mice exposed to 100 ppm of Cu for 8 weeksand to 200 ppm of Cu for either 3 or 8 weeks. Conversely, asignificant increase in the proliferative response to Eschenchiacolilipopolysaccharide (LPS) was observed in mice exposed to50 or 100 ppm of Cu for 3 weeks. However, the response to LPSwas also significantly inhibited following prolonged Cu administration.In contrast, mice exposed to low or high Cu doses during shortor long periods showed increased production of autoantibodiesdirected to bromelain-treated mouse erythrocytes. The DTH responseto sheep red blood cells was not modified following short-termadministration of 100 ppm of Cu, but was depressed after prolongedexposure to this dose of the metal. Significant inhibition ofthe DTH response was observed in mice exposed to 300 ppm ofCu for 5 or 10 weeks. Thus, oral administration of excess Cualtered the immune response in a fashion related to the doseand duration of treatment     

Effects of lactoferrin on the immune response modified by the immobilization stress

Effects of orally administered lactoferrin (LF) on the cellular and humoral immune responses in mice subjected to immobilization stress (IS) were investigated. Here, we demonstrate that long-term IS induced significant suppression of cellular and humoral immune responses in CBAmice. The suppression was attenuated by LF given to mice in drinking water as determined by the number of antibody-forming cells (AFC) in the spleen and the magnitude of delayed type of hypersensitivity (DTH). On the other hand, LF lowered the elevated DTH response in mice exposed to short-term IS (5 h only) on the day of elicitation of the DTH reaction. We also showed that LF up-regulated spontaneous transforming growth factor beta (TGF-beta) production in the cultures of mesenteric lymph node cells derived from short-term stressed mice. This is the first report on the regulatory effect of LF on the immune response modified by the psychic stress and is consistent with other reports on antinociceptive and analgesic actions of LF in experimental animals.     

Perturbations in immune responses induced by concurrent subchronic exposure to arsenic and endosulfan

The metalloid arsenic and the chlorinated insecticide endosulfan are common environmental contaminants. Humans, animals, and birds are exposed to these chemicals through water and food. Although health effects due to either arsenic or endosulfan exposure are documented, the toxicological impact of co-exposure to these environmental pollutants is unpredictable and unknown. The present study was undertaken to assess whether concurrent exposure to arsenic and endosulfan induces significant alterations in immunological functions. Day-old chicks were exposed to 3.7 ppm of arsenic via drinking water and to 30 ppm of endosulfan-mixed feed either individually or concurrently for up to 60 days. All the chicks were vaccinated with Ranikhet disease virus (F-strain; RD-F) on days 1 and 30. During the course of study and at term, parameters of cellular and humoral immunity were determined. None of the treatments altered the absolute body weight or body weight gain, except arsenic significantly reduced weight gain on day 60. Absolute, but not the relative, weights of spleen, thymus and bursa of Fabricius were significantly reduced in all the treatment groups. The metalloid and insecticide combination significantly depressed the ability of peripheral blood and splenic lymphocytes to proliferate in response to antigen RD-F and mitogen Con A. The delayed type hypersensitivity response to 2,4-dinitro-1-chlorobenzene or to PHA-P was also significantly decreased. Nitric oxide production by RD-F or lipopolysaccharide-stimulated peripheral blood and splenic mononuclear cells was significantly suppressed following concurrent exposure to arsenic and endosulfan. Furthermore, the combined exposure also decreased the antibody response to RD-F. The suppression of cellular and humoral immune responses was also evident following administration of individual compounds, and it was not exacerbated following concurrent exposure. To our knowledge, this is the first report describing the suppression of immune responses following exposure to arsenic alone or in combination with endosulfan at environmentally realistic concentrations in avian species. Therefore, immunotoxicological effects induced by concurrent exposure to arsenic and chlorinated pesticides should be considered when assessing the risk to human and animal health.     

Induction of redox changes, inducible nitric oxide synthase and cyclooxygenase-2 by chronic cadmium exposure in mouse peritoneal macrophages

Redox changes and the secretion of inflammatory mediators were investigated in resident peritoneal macrophages of mice chronically exposed to cadmium (Cd, 15 ppm for 2 months) through drinking water. Our results showed that in vivo Cd exposure altered the redox balance in mouse peritoneal macrophages, leading to excessive production of reactive oxygen species (ROS) that overwhelmed the antioxidant defenses. It also led to increased lipid peroxidation and arachidonic acid (AA) release, higher nitric oxide and prostaglandin E(2) (PGE(2)) production, and induction of inducible nitric oxide synthase and cyclooxygenase-2 compared with control macrophages. Oxidative stress and inflammation could be important processes operating in the modulation of mouse macrophage physiology induced by chronic Cd exposure.     

Humoral and cell mediated immune response to cadmium in mice

The effect of 30, 100 and 300 ppm of cadmium chloride (CdCl2) exposure for 35 days on humoral and cell mediated immune response was examined in Swiss Albino mice. Body burden of cadmium in kidney, spleen and liver was determined and histopathology of these organs was also done. Cadmium chloride in doses of 100 and 300 ppm when fed in drinking water caused significant decrease in IgM and IgG titre against sheep red blood cells (SRBC) and a significant decrease in IgG titre against bovine serum albumin (BSA). The delayed type hypersensitivity response to SRBC and splenic T cell proliferation to BSA was also significantly decreased following 100 amd 300 ppm cadmium exposure. Cadmium accumulation in the spleen, liver and kidney was associated with degeneration and inflammatory changes. It is concluded that cadmium causes significant suppression of humoral and cell mediated immune response in mice which could be due to its cytotoxic action on liver, kidney and immune cells.     

HUMORAL AND CELL MEDIATED IMMUNE RESPONSE TO CADMIUM IN MICE

The effect of 30, 100 and 300 ppm of cadmium chloride (CdCl₂) exposure for 35 days on humoral and cell mediated immune response was examined in Swiss Albino mice. Body burden of cadmium in kidney, spleen and liver was determined and histopathology of these organs was also done. Cadmium chloride in doses of 100 and 300 ppm when fed in drinking water caused significant decrease in IgM and IgG titre against sheep red blood cells (SRBC) and a significant decrease in IgG titre against bovine serum albumin (BSA). The delayed type hypersensitivity response to SRBC and splenic T cell proliferation to BSA was also significantly decreased following 100 amd 300 ppm cadmium exposure. Cadmium accumulation in the spleen, liver and kidney was associated with degeneration and inflammatory changes. It is concluded that cadmium causes significant suppression of humoral and cell mediated immune response in mice which could be due to its cytotoxic action on liver, kidney and immune cells.     

Altered immune response during cadmium administration in mice

C57BL/6 mice were administered 50 or 200 ppm of Cd as CdCl2 in the drinking water for either 3 to 4 (short term) or 9 to 11 (long term) weeks. In other experimental designs, mice were exposed orally to 300 ppm of Cd or injected with 2.5 mg/kg of Cd ip. The proliferative response to the T cell mitogens Con A and PHA was increased in cultures of spleen cells from orally treated mice in most of the experiments performed. After primary immunization with sheep red blood cells, the number of IgM antibody forming cells per 10(7) spleen cells was also moderately higher in mice exposed to 50 or 200 ppm of Cd for short or long term. In contrast, long-term exposure to 300 ppm of Cd depressed the antibody response to SRBC. Administration of ZnCl2 prevented the enhancement of the PFC response in mice orally administered 50 ppm of Cd. The capacity to suppress the antibody response of spleen cells preincubated with sodium periodate was decreased after short-term oral or ip. Cd administration but was completely or partially recovered after long-term exposure to either 50 or 200 ppm of Cd.     

The use of minimum selectable concentrations (MSCs) for determining the selection of antimicrobial resistant bacteria

The use of antimicrobial compounds is indispensable in many industries, especially drinking water production, to eradicate microorganisms. However, bacterial growth is not unusual in the presence of disinfectant concentrations that would be typically lethal, as bacterial populations can develop resistance. The common metric of population resistance has been based on the Minimum Inhibitory Concentration (MIC), which is based on bacteria lethality. However, sub-lethal concentrations may also select for resistant bacteria due to the differences in bacterial growth rates. This study determined the Minimal Selective Concentrations (MSCs) of bacterial populations exposed to free chlorine and monochloramine, representing a metric that possibly better reflects the selective pressures occurring at lower disinfectant levels than MIC. Pairs of phylogenetically similar bacteria were challenged to a range of concentrations of disinfectants. The MSCs of free chlorine and monochloramine were found to range between 0.021 and 0.39?mg?L^?1, which were concentrations 1/250 to 1/5 than the MICs of susceptible bacteria (MIC _susc ). This study indicates that sub-lethal concentrations of disinfectants could result in the selection of resistant bacterial populations, and MSCs would be a more sensitive indicator of selective pressure, especially in environmental systems.     

Dietary methoxychlor exposure modulates splenic natural killer cell activity, antibody-forming cell response and phenotypic marker expression in F0 and F1 generations of Sprague Dawley rats

Methoxychlor, a chlorinated hydrocarbon pesticide, is a persistent environmental contaminant that has been identified in human reproductive tissues. Methoxychlor has been shown to be estrogenic in both in vivo and in vitro studies. As an endocrine disrupter, it may have the potential to adversely affect endocrine, reproductive, and immune systems in animals. The present study evaluated methoxychlor's immunotoxic potential in F0 (dams) and F1 generations of Sprague Dawley rats exposed to an isoflavone-free diet containing methoxychlor at concentrations of 10, 100, and 1000 ppm. In dams, exposure to methoxychlor from gestation day 7 to postpartum day 51 (65 days total exposure) produced a significant increase in the NK activity (1000 ppm) and the percentages of T cells (1000 ppm), helper T cells (1000 ppm) and macrophages (100 and 1000 ppm). In contrast, a decrease in the numbers of splenocytes and B cells was observed at the 100 and 1000 ppm concentrations. In F1 males, exposure to methoxychlor gestationally, lactationally and through feed from postnatal day 22-64 (78 days total exposure) produced an increase in the spleen IgM antibody-forming cell response to sheep red blood cells (100 and 1000 ppm) and the activity of NK cells (1000 ppm). However, there was a decrease in the terminal body weight (1000 ppm), spleen weight (1000 ppm), thymus weight (100 and 1000 ppm), and the numbers of splenocytes (1000 ppm), B cells (100 and 1000 ppm), cytotoxic T cells (1000 ppm) and NK cells (100 and 1000 ppm). In F1 females, exposure to methoxychlor produced a decrease in the terminal body weight (1000 ppm) and the percentages of cytotoxic T cells (10, 100 and 1000 ppm). These results demonstrate that developmental and adult dietary exposure to methoxychlor modulates immune responses in Sprague Dawley rats. Immunological changes were more pronounced in the F1 generation male rats that were exposed during gestation and postpartum, when compared to the F0 and F1 generation females. Increases in antibody-forming cell response and NK cell activity, and altered spleen cell subpopulation numbers were observed in the F1 generation male rats, without similar changes to the F1 generation females.     

Immunotoxicity and disease resistance in Japanese quail (Corturnix coturnix japonica) exposed to malathion

The purpose of this study was to evaluate the impact of malathion on the immune system of wild birds, using Japanese quail (Coturnix coturnix japonica) as a model. Quail were exposed to malathion in drinking water at environmentally realistic concentrations (0 ppm, 1 ppm, and 10 ppm). In the fifth week, several arms of the immune response were tested using the T-cell based phytohemagglutinin (PHA) skin test, the B-cell mediated antibody response, and the chemiluminescence assay measuring innate immunity. After the sixth week of malathion exposure, quail were challenged with E. coli O2. The bursa of Fabricius and the spleen were assessed for histopathology. No clinical signs of malathion toxicity were observed. Morbidity or mortality subsequent to E. coli exposure tended (P = 0.08) to be higher in the high exposure group (50.0%) compared to the control (22.2%) group. There was no difference in the innate immune response in the malathion exposed birds, however, humoral immunity was suppressed (P = 0.03) with the higher malathion exposure. Histopathological evaluation revealed an immunosuppressive effect of malathion on the bursa of Fabricius; bursal atrophy, decreased B-cell density and increased apoptosis in the medulla, and increased connective tissue thickness of the follicular epithelium. Antibody suppression was correlated with bursal changes and peripheral blood lymphocyte count, the organ and cells involved in antibody production. Following the same pattern as other immunotoxicity tests, the PHA T-cell proliferative response also tended to be suppressed in the high exposure group. This study provides evidence that subchronic, moderate malathion exposure is immunotoxic to quail and that testing integrated, functional immunity using an infectious challenge is a better predictor of immunotoxicity than individual responses to immunotoxicity tests. The secondary antibody response, circulating lymphocyte populations, and bursal histopathology were the most sensitive indicators of immune status, as these predicted decreased disease resistance with malathion exposure.     

Exposure to lead during critical windows of embryonic development: differential immunotoxic outcome based on stage of exposure and gender.

Previous rat studies with lead (Pb) have shown that exposure throughout the full gestational period results in persistent immunotoxicity detectable in both juvenile and adult offspring. Gender differences are also evident. However, little is known about the persistent immunotoxic effects of Pb when administered during specific stages of embryonic development. Adult Sprague-Dawley female rats were administered Pb acetate (or control acetate) in their drinking water early in gestation (days 3-9) or late in gestation (days 15-21). Significantly depressed delayed type hypersensitivity (DTH) responses as well as elevated IL-10 production, relative monocyte numbers, and increased relative thymic weights were observed in late-gestation Pb-exposed female offspring assessed as adults. In contrast, late-gestation Pb-treated male offspring had significantly increased IL-12 production and decreased IL-10 production, while the DTH response, relative monocyte numbers and thymic weights were unchanged. With early exposure, the primary alteration was decreased nitric oxide production in Pb-treated males, whereas in Pb-treated females nitrite production was unaltered. These results suggest that at the Pb dosage employed, the embryo may be more sensitive to the full range of Pb-induced immunotoxic effects with late gestational Pb exposure, and the effects of Pb on DTH function are more pronounced in females. The data also indicate that adherent splenocytes (probably macrophages) and T lymphocytes are the primary immune cells affected during fetal Pb exposure, and that gender may influence the impact of Pb exposure on these cells. Therefore, additional developmental immunotoxicity studies are needed to examine critical windows of immune development for immunotoxicity and differential susceptibility based on gender.     

Hypertension and associated cardiovascular abnormalities induced by chronic barium feeding

Because high barium concentrations (2-10 ppm) in human drinking water have been reported to be associated with elevated cardiovascular mortality, hypertension and other cardiovascular effects were sought in rats chronically exposed for 1-16 mo to drinking water containing 1, 10, or 100 ppm barium. From weaning, female Long-Evans rats were kept in a "low contamination" environment and fed a diet low in trace metals. Their drinking water was deionized, fortified with 5 essential trace metals, and either 0, 1, 10, or 100 ppm barium was added. Indirect systolic pressure of unanesthetized rats was measured in triplicate at 1, 2, 4, 8, 12, and 16 mo. Average systolic pressure increased significantly after exposure to 100 ppm barium for 1 mo or longer and after exposure to 10 ppm barium for 8 mo or longer. After 4 or 16 mo, barium exposure failed to alter organ weights or tissue concentrations of calcium, magnesium, sodium, or potassium; however, both 10 and 100 ppm barium resulted in significant increases in tissue barium. Rats exposed to 100 ppm Ba for 16 mo exhibited depressed rates of cardiac contraction and depressed electrical excitability in the heart. Hearts from these maximally exposed rats also had significantly lower ATP content and phosphorylation potential, as measured by 31P NMR spectroscopy. Although the barium-induced increase in the blood pressure of rats was modest, comparable mild hypertension in humans would have major health implications.     

Ingestion of chlorinated water has no effect upon indicators of cardiovascular disease in pigeons

Cardiovascular disease (CVD) accounts for nearly half the deaths, yearly, in the United States. The arterio(athero)sclerotic plaque is the principal lesion of CVD. The White Carneau (WC) pigeon is an animal model that has been employed extensively for studying CVD. Cholesterol (CHOL) feeding aggravates atherosclerosis in WC pigeons greater than 2 years old. In 1986, two reports appeared from a single laboratory claiming a direct effect of drinking chlorinated (Cl) water upon lipid levels and plaque development in young (less than 1 year) WC pigeons. These are the only reports of such direct effects, to date. Three months' exposure to 2 ppm or 15 ppm Cl in the drinking water, resulted in increased circulating CHOL levels in young male WC pigeons fed a normocholesterolemic (NC) diet in which Ca2+ levels were reduced. In addition, at both Cl concentrations there was a significant increase in plaque size, compared to controls. Pigeons in the 2 ppm group also exhibited elevated low density lipoprotein (LDL) levels after 3 months on the NC diet. These findings, if extrapolated to man, could have considerable public health consequences, since nearly 200 million people in the United States drink Cl water. We have carried out a similar set of studies but with strikingly different results. We used the same suppliers of pigeons and feed as did the authors of the 1986 reports and followed their approach where possible. Six month-old male WC pigeons drank water with 2 ppm or 15 ppm Cl (pH 8.5) and ate a NC diet with Ca2+ reduced to 80% of normal. At both 1 and 3 months, body weight, CHOL, triglyceride and LDL levels were unaffected by drinking Cl water. There was also no effect of Cl water on plaque size after 3 months. Thus, we found no evidence that drinking chlorinated water has any effect upon circulating lipid levels or upon the development of arteriosclerotic plaques, in this animal model.     

Effects of the color additive caramel color III and 2-acetyl-4(5)-tetrahydroxybutylimidazole (THI) on the immune system of rats.

Administration of ammonia caramel color (AC) to rats may decrease blood lymphocyte counts, specifically in rats fed a diet low in vitamin B6. This effect is associated with 2-acetyl-4(5)-(1,2,3,4-tetrahydroxybutyl)imidazole (THI). To characterize and compare the effects of AC and THI and to study the influence of dietary pyridoxine, two studies in rats were conducted. Weanling rats fed a diet containing 2-3 ppm pyridoxine and exposed to 4% AC or 5.72 ppm THI in drinking water for 4 weeks showed reduced cell numbers in spleen and popliteal lymph nodes, as well as in the blood. Flow cytometric analyses demonstrated a comparable reduction in B and T lymphocytes. In blood, spleen, and popliteal lymph nodes, CD4+ lymphocytes were more reduced than CD8+ cells. The number of bone marrow cells was not affected. Although thymus weight and cell number were not affected either, a decreased cortex over medulla area ratio and an increase in medullary cell density largely due to an increase in CD4+ thymocytes was observed. Decreased numbers of ED2+ macrophages were observed in the thymic cortex and in the spleen red pulp. All effects observed were either less pronounced or absent in a study with rats fed a diet containing 11-12 ppm pyridoxine. The effects of AC and THI on the immune system were similar. Whereas AC exposure was associated with changes in vitamin B6 status, THI did not induce obvious effects on vitamin B6 parameters. It is proposed that the effects of AC and THI on the immune system are not caused by a disturbance of vitamin B6 metabolism, but may in fact result from a disturbance of a specific PLP-dependent process.     

Determination of toxicity of subacute treatment of some plant growth regulators on rats

The effects of some plant growth regulators (PGRs), 2,3,5-triiodobenzoic acid (TIBA), Naphthaleneacetic acid (NAA) and 2,4-Dichlorofenoxyacetic acid (2,4-D), at sublethal concentrations on antioxidant defense system [glutathione peroxidases (GPx), reduced glutathione (GSH), glutathione reductase (GR), glutathione-S-transferase (GST) and catalase (CAT)], immune potential enzymes [adenosine deaminase (ADA) and myeloperoxidase (MPO)], and lipid peroxidation content [Malondialdehyde, (MDA)] were investigated in lung and speen tissues of rats. Sprague-Dawley albino rats were exposed to 0, 50, or 100 ppm (parts per million) TIBA, NAA, or 2,4-D in drinking water ad libitum for 25 days continuously. According to the results, MDA concentration significantly increased in the tissues treated with 100 ppm dosage of NAA or 2,4-D without any change in the tissues of rats treated with both dosage of TIBA. The GSH depletion in the spleen tissue of rats treated with both the dosage of NAA and 2,4-D were found to be significant. Also, GSH level in the spleen was significantly reduced with 100 ppm of 2,4-D and NAA. The activity of antioxidant enzymes were also seriously affected by PGRs; GPx significantly decreased in the lung of rats treated with both dosages of the PGRs, whereas GPx activity in the spleen were significantly increased with 100 ppm dosage of 2,4-D and NAA. On the other hand, CAT activity significantly decreased in the lung of rats treated with both dosages of NAA, 100 ppm of 2,4-D and 50 ppm of TIBA, and also in the spleen treated with 50 ppm NAA and 2,4-D. The ancillary enzyme GR activity significantly decreased in the spleen with both doses of the PGRs, also in the lung treated with both dosages of 2,4-D, 50 ppm of NAA and 100 ppm of TIBA. The drug metabolizing enzyme GST activity significantly reduced in the lung of rats treated with both dosages of the PGRs and also in the spleen treated with 100 ppm dosage of 2,4-D and TIBA and 50 ppm of NAA. Meanwhile, immune potential enzyme MPO activity significantly increased in the spleen of rats treated with both doses of NAA and TIBA whereas ADA activity significantly decreased in the spleen of rats treated with 100 ppm dose of NAA and TIBA. The observations presented led us to conclude that the administrations of subacute NAA, 2,4-D, and TIBA promote MDA content, inhibit the antioxidative defense system and activate or inhibit immune potential enzymes in the rat's spleen and lung tissues. These data suggest that PGRs produced substantial organ toxicity in the lung and spleen during the period of a 25-day subacute exposure.     

Evaluation of developmental neurotoxicity of organotins via drinking water in rats: dimethyl tin

Dimethyltin (DMT) is one of several organotins that are detected in domestic water supplies due to their use as plastic stabilizers for polyvinyl chloride (PVC) and chlorinated PVC (CPVC) products. A limited number of in vitro and in vivo studies suggest that DMT may produce developmental neurotoxicity; therefore, we initiated studies to evaluate long-term neurobehavioral changes in offspring following perinatal exposure. In the first study, female Sprague–Dawley rats were exposed via drinking water to DMT (0, 3, 15, 74 ppm) before mating and throughout gestation and lactation. Male offspring were tested for changes in: 1) preweaning learning in an associative runway task, 2) motor activity ontogeny, 3) spatial learning and retention in the Morris water maze as adults, 4) brain weight, 5) biochemical evidence of apoptosis, and 6) neuropathology. DMT toxicity was expressed as depressed maternal weight gain (74 ppm), and in the offspring, decreased brain weight (3, 74 ppm), decreased apoptosis (all concentrations), mild vacuolation in adult offspring (all concentrations), and slower learning in the water maze (15 ppm) due to altered spatial search patterns. In a second study, DMT exposure (same concentrations) occurred from gestational day 6 to weaning. Male and female offspring were tested. The high concentration again depressed maternal weight gain, decreased offspring birth weight and preweaning growth, and decreased brain weight. Increased and decreased apoptotic markers were measured, depending on age. Learning deficits were observed in the runway at postnatal day 11 (15, 74 ppm) and again in the adult offspring in the water maze (15 ppm). The results of both studies demonstrate a reproducible effect of 15 ppm perinatal DMT exposure on spatial learning. Changes in expression of apoptosis, brain weight, and the occurrence of neuropathological lesions also indicate potential neurotoxicity of DMT. These results were in contrast to earlier findings with monomethyl tin, for which only similar neuropathological lesions were observed. Thus, developmental neurotoxicity may be produced in offspring following gestational exposure to DMT in drinking water.     

Developmental immunotoxicity of lead in the rat: influence of maternal diet

The effect of maternal dietary protein intake on lead-induced developmental immunotoxicity was studied in female Fischer 344 rats receiving lead acetate (250 ppm) or sodium acetate (control) in the drinking water during breeding and pregnancy until parturition. Dams were fed isocaloric diets (either 20% casein or 10% casein) from 2 wk prior to mating until the end of lactation. After weaning, dams and female offspring were given the 20% casein diet and regular water. Immune function was assessed in dams at 8 wk postpartum and in offspring at 13 wk of age. Dams showed no marked difference in any of the immune endpoints examined, regardless of diet or lead treatment. In contrast, lead exposure during early development produced a subsequent significant reduction of both the delayed-type hypersensitivity response and interferon gamma production in adult offspring independent of maternal diet. Lead-exposed offspring from the high-dietary-protein group had significantly elevated production of both interleukin-4 and tumor necrosis factor alpha(TNF-alpha) with increased relative spleen weight and a decreased body weight compared to offspring in the lead control group. In contrast, lead-exposed offspring from dams receiving the low-protein diet had no marked change in TNF-alpha levels, relative spleen weight, or body weight, while interleukin-4 levels were significantly reduced compared with the lead control group. In conclusion, maternal dietary protein intake can modulate the immunotoxic effects of lead exposure during early development. This occurred at levels of protein intake and doses of lead exposure that produced no detectable effect on the maternal immune system.     

Human and experimental studies on renal eicosanoid response to long-term cadmium exposure.

In order to assess the effects of long-term exposure to cadmium (Cd) on the renal metabolism of eicosanoids, the urinary excretion of 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha), and thromboxane B2 (TXB2) was determined in 37 workers exposed to Cd and in female Sprague-Dawley rats given 100 ppm Cd in drinking water for 10 months. Urinary output of sodium and calcium was also determined. The Cd-exposed workers showed an increased urinary concentration of 6-keto-PGF1 alpha, PGE2, sodium, and calcium. The rise of 6-keto-PGF1 alpha was related to Cd levels in blood and weakly correlated with urinary sodium. Calcium in urine was not related to the concentration of the metal in blood and urine. A slight elevation in urinary TXB2 was also observed in workers with blood Cd higher than 5 micrograms/liter. After 10 months of exposure to Cd, female Sprague-Dawley rats presented an enhanced urinary excretion of albumin, transferrin, beta 2-microglobulin, sodium, and PGE2 in urine. The latter was significantly correlated with albuminuria and transferrinuria. In conclusion the results show that chronic exposure to Cd induces changes in the urinary excretion of some eicosanoids. The possible relation of these changes to Cd-induced kidney dysfunction are discussed.