Toxicity In Laboratory Animals Research Articles

Study of blood analysis of laboratory animals with subchronic oral toxicity of the drug Amoxiyantar

The article presents the results of studies of subchronic oral toxicity in laboratory animals of the new veterinary drug Amoxiantar. The studies were carried out as part of a laboratory-experimental (preclinical) study of a medicinal product with the aim of introducing it into clinical veterinary practice. Our goal was to study the effect of Amoxiantar on the hematological and biochemical parameters of the blood of laboratory animals. Three experimental groups were formed, of which two experimental and one control, consisting of white outbred rats, 10 animals each. The drug was administered to animals daily intragastrically for 15 days, rats of the first experimental group at a dose of 150 mg/kg body weight, rats of the second group 15 mg/kg body weight, the control group was injected with distilled water. Blood was taken on the first and tenth days after the completion of the administration of the Amoxiantar preparation, on the 16th and 25th day of the experiment, respectively. Statistical processing of the results of the general clinical analysis of the blood of animals on the tenth day after the completion of the drug (25 days of the experiment) revealed monocytosis in the blood of the first and second experimental groups and leukocytosis in the first experimental group compared with the control group, however, these values were normal rat blood parameters. The revealed statistically significant differences, on the 25th day of the experiment, between the second experimental group and the control group in terms of AST, alkaline phosphatase and creatinine were clinically insignificant. During the 25th day of the subchronic experiment, the new veterinary drug Amoxiantar did not adversely affect the hematological and biochemical blood parameters of laboratory animals at doses of 15 and 150 mg/kg of animal body weight.

Interactions of perfluorooctanoic acid with acyl-CoA thioesterase 1 (Acot1)

Perfluorooctanoic acid (PFOA), a typical representative of per- and polyfluoroalkyl substances (PFASs), is a widely utilized persistent organic pollutant (POP) known to induce liver toxicity in laboratory animals and wildlife. Evidence suggests that PFOA interacts with Acyl-CoA thioesterase 1 (Acot1) to modulate levels of β-oxidation. Specifically, PFOA accelerates β-oxidation, while Acot1 is inhibitory. Few studies have investigated the specific relationship between PFOA and Acot1 and the mechanism of their interaction remains unclear. In the following study, purified rat Acot1 protein was synthesized via bacterial recombination and the structural features that facilitate its binding to PFOA were assessed via molecular docking technology. Additionally, through use of circular dichroism spectroscopy (CD) and isothermal titration calorimetry (ITC) we demonstrate that PFOA binds to WT-Acot1 through electrostatic attraction and low strength non-covalent hydrogen bonding at a molar ratio of 1:1. Furthermore, we identify N326 and H373 amino acid residues as key regulators of the binding process. Together, these findings clarify the interaction pattern of PFOA and Acot1 proteins and provide insight into the specific molecular mechanisms that induce PFOA toxicity in humans and animals.

Effects of intrauterine exposure of perfluoroalkyl and polyfluoroalkyl substances on growth and development of offspring

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are a new subgroup of the persistent organic pollutants that have been widely used in industrial production and daily life for over 60 years. The presence of PFASs can be detected in rivers, soil, humans and wildlifes. Studies have shown that PFASs can induce multi-system toxicity in laboratory animals, including liver toxicity, neurotoxicity, reproductive and developmental toxicity, endocrine toxicity and immunotoxicity. PFASs are closely related to the birth outcomes, growth and development of the offspring. PFASs primarily impair the health of the offspring by regulating peroxisome proliferators-activated receptors pathways, interfering with estrogen, affecting the thyroid system, glucocorticoids, inflammatory responses, and DNA methylation. Thus, more large-scale longitudinal cohort studies should be conducted and more in-depth potential mechanisms of action should be explored to clarify the relationship between intrauterine exposure of PFASs and birth outcomes, growth and development of offspring.

A Pathology Review of the Lower Gastrointestinal Tract in Relation to Ulcerative Colitis in Rats and Cynomolgus Macaques Treated With Ammonium Perfluorooctanoate.

Among many short-term, subchronic, and chronic toxicology studies with ammonium perfluorooctanoate (PFOA), the gastrointestinal tract has not been identified as a target organ for PFOA-related toxicity in laboratory animals where the corresponding serum PFOA concentrations typically approach several orders of magnitude higher than the general human population. These lack of gastrointestinal tract-related findings were in direct contrast to an epidemiological observation where a positive trend was observed for ulcerative colitis, an idiopathic chronic inflammatory condition of the gut, in a Mid-Ohio River community whose drinking water contained higher levels of PFOA. This study was conducted to perform a histological reevaluation of large intestine sections in laboratory animals from 2 long-term toxicological studies: one was with Sprague Dawley rats that received ammonium PFOA in their diet for 2 years and the other one was with cynomolgus macaques that received daily capsules of ammonium PFOA for 6 months. In both studies, there was a lack of histological evidence of treatment-related inflammatory lesions that was suggestive of the occurrence of ulcerative colitis in these laboratory animals even under the most rigorous treatment schedules. These findings do not offer support for the biological plausibility of the epidemiological associations reported.

BIOCHEMICAL MARKERS OF DAMAGE IN RATS EXPOSED BY ORAL GAVAGE TO SINGLE-WALLED CARBON NANOTUBES IN COMBINATION WITH ANTIOXIDANT PREPARATION “AEVIT”

Introduction. The toxicity of carbon nanotubes (CNT), which are chemically inert particles, is thought to be connected with responses of aseptic inflammation and oxidative stress. This study was conducted to determine how far antioxidants may reduce CNT toxicity in laboratory animals. Material and methods. Male Wistar rats were administered by oral gavage with 0.05 or 0.5 mg/kg/day of Tuball© single-walled CNT in vegetable oil for 2 weeks, without a modifier or in combination with Aevit© (mixture of retinol and α-tocopherol given in doses 25,000 IU/kg/day and 25 mg/kg/day correspondingly). Control animals received oil or Aevit without CNT. 10 markers of oxidative stress and 12 clinical chemistry markers were determined in the rat blood samples. Results. Aevit didn’t influence the above biochemical markers, but combination “Aevit + CNT” increased the prooxidant action of CNT and arose biochemical signs of malabsorption, presumably as a result of retinol inhibitory action onto repair of intestinal epithelial cells, damaged by CNT. Discussion. The lack of tocopherol protective action, which usually removes prooxidant effects of high retinol concentrations, can be explained by superposition of two mechanisms: 1) two components of Aevit, in the presence of CNT, may be separated in space, since only retinol has isoprenoid side chain needed for the formation of donor-acceptor complexes with CNT surface; 2) the effects of retinol on cell reproduction, differentiation and wound healing is not related to its anti - or pro-oxidant properties but takes place at the level of target genes transcription after binding of retinoic acid with nuclear receptors RARs and RXRs. The data obtained allowed supposing the mechanism of lung cancer increases in ATBC and CARET trials was not prooxidant action of retinol and its precursor β-carotene, but regulatory inhibition of lung epitheliocytes reparation during its continued damage by cigarette smoke and asbestos fibers by retinoic acid. Conclusion. Aevit (and, probably, other retinoid-containing preparations) can’t be recommended to ensure the safety of humans and animals during oral CNT intake. The results obtained explanation needs both functional activities of retinol, which is simultaneously antioxidant and one of the nuclear regulators; this, in turn, leads to the new assumption about the mechanisms of unsuccessful outcomes in ATBC and CARET trials.

Concerns over use of glyphosate-based herbicides and risks associated with exposures: a consensus statement.

The broad-spectrum herbicide glyphosate (common trade name “Roundup”) was first sold to farmers in 1974. Since the late 1970s, the volume of glyphosate-based herbicides (GBHs) applied has increased approximately 100-fold. Further increases in the volume applied are likely due to more and higher rates of application in response to the widespread emergence of glyphosate-resistant weeds and new, pre-harvest, dessicant use patterns. GBHs were developed to replace or reduce reliance on herbicides causing well-documented problems associated with drift and crop damage, slipping efficacy, and human health risks. Initial industry toxicity testing suggested that GBHs posed relatively low risks to non-target species, including mammals, leading regulatory authorities worldwide to set high acceptable exposure limits. To accommodate changes in GBH use patterns associated with genetically engineered, herbicide-tolerant crops, regulators have dramatically increased tolerance levels in maize, oilseed (soybeans and canola), and alfalfa crops and related livestock feeds. Animal and epidemiology studies published in the last decade, however, point to the need for a fresh look at glyphosate toxicity. Furthermore, the World Health Organization’s International Agency for Research on Cancer recently concluded that glyphosate is “probably carcinogenic to humans.” In response to changing GBH use patterns and advances in scientific understanding of their potential hazards, we have produced a Statement of Concern drawing on emerging science relevant to the safety of GBHs. Our Statement of Concern considers current published literature describing GBH uses, mechanisms of action, toxicity in laboratory animals, and epidemiological studies. It also examines the derivation of current human safety standards. We conclude that: (1) GBHs are the most heavily applied herbicide in the world and usage continues to rise; (2) Worldwide, GBHs often contaminate drinking water sources, precipitation, and air, especially in agricultural regions; (3) The half-life of glyphosate in water and soil is longer than previously recognized; (4) Glyphosate and its metabolites are widely present in the global soybean supply; (5) Human exposures to GBHs are rising; (6) Glyphosate is now authoritatively classified as a probable human carcinogen; (7) Regulatory estimates of tolerable daily intakes for glyphosate in the United States and European Union are based on outdated science. We offer a series of recommendations related to the need for new investments in epidemiological studies, biomonitoring, and toxicology studies that draw on the principles of endocrinology to determine whether the effects of GBHs are due to endocrine disrupting activities. We suggest that common commercial formulations of GBHs should be prioritized for inclusion in government-led toxicology testing programs such as the U.S. National Toxicology Program, as well as for biomonitoring as conducted by the U.S. Centers for Disease Control and Prevention.

Зависимость биологической активности бактерий Bacillus Sp. из многолетнемерзлых пород от температуры

Fossil bacteria in permafrost evolutionarily adapted to low temperatures (-5ºC), modern probiotics bacteria are adapted to living in warm-blooded animals (37ºC). It was found that at -5ºC, the enzymatic activity of fossil bacteria Bacillus sp. MG8 is a minimal strain. At lowering the incubation temperature to -16ºC, the enzymatic activity of bacte-ria MG8 increases in 3 times, at the temperature 42ºC - in a 1.5times relative IP5832 strain probiotic bacteria Bacillus cereus. Fossil strain Bacillus sp. MG8 and probiotic bacterial strain B.cereus IP5832 at incubation temperature 37ºC practically don’t differ from each other in the enzymatic activity in vitro and toxicity in laboratory animals in vivo. Incubation fossil bacteria Bacillus sp. at -5ºC allows to reduce their toxicity in warm-blooded animals in 5 times in comparison with Bacillus cereus JP5832, and to increase immunostimulating effect in the doses from 0,005•106 to 50•106 microbial cells per mouse. The obtained data show that fossil saprophytic bacteria strain MG8 Bacillus sp. from permafrost are less toxic to modern mammals than even bacilli-probiotics for medical purposes.

In vitro exposure of DE‐71, a penta‐PBDE mixture, on immune endpoints in bottlenose dolphins (Tursiops truncatus) and B6C3F1 mice

Polybrominated diphenyl ethers (PBDEs) are an emerging contaminant of concern with low level exposures demonstrating toxicity in laboratory animals and wildlife, although immunotoxicity studies have been limited. Bottlenose dolphin peripheral blood leukocytes (PBLs) and mouse splenocytes were exposed to environmentally relevant DE-71 (a penta-PBDE mixture) concentrations (0-50 µg ml(-1) ) in vitro. Natural killer (NK) cell activity and lymphocyte (B and T cell) proliferation were evaluated using the parallelogram approach for risk assessment. This study aimed to substantiate results from field studies with dolphins, assess the sensitivities between the mouse model and dolphins, and to evaluate risk using the parallelogram approach. In mouse cells, NK cell activity increased at in vitro doses 0.05, 0.5 and 25 µg DE-71 ml(-1) , whereas proliferation was not modulated. In dolphin cells, NK cell activity and lymphocyte proliferation was not altered after in vitro exposure. In vitro exposure of dolphin PBLs to DE-71 showed similar results to correlative field studies; NK cell activity in mice was more sensitive to in vitro exposure than dolphins, and the parallelogram approach showed correlation with all three endpoints to predict risk in bottlenose dolphins.

Essential Role of the Cytochrome P450 Enzyme CYP2A5 in Olfactory Mucosal Toxicity of Naphthalene

Naphthalene (NA), a ubiquitous environmental pollutant that can cause pulmonary and nasal toxicity in laboratory animals, requires cytochrome P450 (P450)-mediated metabolic activation to cause toxicity. Our recent study using a Cyp2f2-null mouse showed that CYP2F2 plays an essential role in NA-induced lung toxicity, but not in NA-induced nasal toxicity. The aim of this study was to determine whether mouse CYP2A5, abundantly expressed in nasal olfactory mucosa (OM) and the liver, but less in the lung, plays a major role in the bioactivation and toxicity of NA in the OM. We found, by comparing Cyp2a5-null and wild-type (WT) mice, that the loss of CYP2A5 expression led to substantial decreases in rates of NA metabolic activation by OM microsomes. The loss of CYP2A5 did not cause changes in systemic clearance of NA (at 200 mg/kg, i.p.). However, the Cyp2a5-null mice were much more resistant than were WT mice to NA-induced nasal toxicity (although not lung toxicity), when examined at 24 hours after NA dosing (at 200 mg/kg, i.p.), or to NA-induced depletion of total nonprotein sulfhydryl in the OM (although not in the lung), examined at 2 hours after dosing. Thus, mouse CYP2A5 plays an essential role in the bioactivation and toxicity of NA in the OM, but not in the lung. Our findings further illustrate the tissue-specific nature of the role of individual P450 enzymes in xenobiotic toxicity, and provide the basis for a more reliable assessment of the potential risks of NA nasal toxicity in humans.

Phthalate exposure among pregnant women in Jerusalem, Israel: Results of a pilot study

Background Phthalates can disrupt endocrine function and induce reproductive and developmental toxicity in laboratory animals. Few studies have evaluated exposure to phthalates in pregnant women, despite the potential sensitivity of the developing fetus to adverse effects of phthalates. Methods We measured urinary concentrations of 11 phthalate metabolites in 19 pregnant women, recruited in Jerusalem, Israel in 2006, and collected questionnaire data on demographic factors and consumer habits from these women. We compared geometric mean concentrations in subgroups and used the Mann–Whitney U-test for independent samples to determine significant differences between groups. Results Nine metabolites were detected in at least 95% of the samples: mono(2-ethyl-5-carboxypentyl) phthalate, mono(2-ethyl-5-hydroxyhexyl) phthalate, mono(2-ethyl-5-oxohexyl) phthalate, mono(3-carboxypropyl) phthalate, mono( n-butyl) phthalate, monobenzyl phthalate (MBzP), monoethyl phthalate (MEP), mono(2-ethylhexyl) phthalate and monoisobutyl phthalate. Phthalate metabolite concentrations in these pregnant women were remarkably similar to those in the general United States female population. MBzP geometric mean concentrations were higher in women living in buildings existing 40 years or more ( P = 0.04). In women who used four or more personal care products (perfume, deodorant, lipstick, nail polish, or hand/face cream) in the 48 h prior to providing the urine sample, geometric mean MEP concentrations were more than 4 times higher than concentrations in women using only two or three of the aforementioned products ( P = 0.07). Conclusions Pregnant women in Jerusalem are exposed to a wide range of phthalates. Building materials used in old constructions may be a source of exposure to benzylbutyl phthalate, the parent compound of MBzP. Personal care products may be sources of exposure to diethyl phthalate, the parent compound of MEP.

Internal Exposure and Variability of Phthalate Metabolites in German Men Visiting an Outpatient Clinic For Fertility Work-Up

MAA4-PD-01 Session Title: Biomolecular Methods (II) Introduction: There is scientific and public concern about phthalates that are associated with reproductive toxicity in laboratory animals and are hormonally active. The general population is exposed to phthalates through nutrition, consumer products, and medical devices. The purpose of the present evaluation was to determine intraindiviual variability of internal phthalate exposure and its general values among men in Germany. Methods: We recruited 335 men, part of subfertile couples referred to the Centre of Dermatology and Andrology of the University, Giessen, Germany, for a fertility work-up between April 2004 and October 2005. They completed a questionnaire on nutrition, lifestyle, health status, and environmental worry and gave single spot urines. Secondary metabolites of Di(2-ethylhexyl)phthalate (DEHP), mono-(2-ethyl-5-oxohexyl)phthalate (MEOHP), and mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) next to the monoester metabolite monoethylhexylphthalate (MEHP) were analyzed. In subgroups other phthalate metabolites were determined (eg, MnBP, MiBP, MBzP, 7OH-MeOP). Subjects were asked to participate in the study several times during their clinical appointments. Results: The concentrations of phthalate metabolites of 306 men (age: median = 34 years; body mass index: median, 25.99 kg/m2) were analyzed. Study group median (75th percentile; 95th percentile) concentrations were, in micrograms: MEHP (n = 297) 4.99 (10.85; 30.05), MEOHP (n = 306) 13.32 (26.21; 84.04), MEHHP (n = 306) 10.20 (18.83; 66.64), MCHP (n = 258) 16.23 (32.20; 87.94), MnBP (n = 259) 32.71 (56.70; 165.81), MiBP (n = 137) 49.65 (79.03; 166.23), 7OH-MeOP (n = 136) 4.19 (8.26; 26.58), 7oxo- sum (n=129) 1.98 (3.78; 10.11), MBzP (n = 258) 5.05 (9.33; 28.55), DEHP-metabolites (σ[MEHP, MEOHP, MEHHP, MCHP], n = 249) 46.46 (92.46; 280.23), sum of endocrine-relevant metabolites (σ[MEHP, MEOHP, MEHHP, MCHP, MnBP, MBzP], n = 247) 98.58 (183.98; 525.79), and sum derived from Swan et al 2005 (σ[MiBP, MnBP, MBzP], n = 136) 100.63 (161.4; 390.20). Results can be compared with those of NHANES (2005, eg, median concentrations (75th percentile; 95th percentile) in micrograms for adults: MEHP = 4.1 (9.4; 33.3), MEOHP = 17.7 (25.9; 115), and MEHHP = 12.2 (39.8; 175), n=1647). For 70 men, 2 spot urines within a period of 4–6 weeks were evaluated. Intraindividual variability of metabolite concentrations was small, for example, Wilcoxon Signed-Rank test for MEHP: P = 0.64; MEOHP: P = 0.71; MEHHP: P = 0.78). Discussion: Phthalate metabolites, especially secondary metabolites of DEHP analyzed in the scope of this study, are considered to be very specific for determining internal phthalate exposure. Concentrations determined in single spot urine were in similar range to the results of NHANES. According to this evaluation, variability is judged to be of expected range confirming preliminary results of smaller study groups. Further analyses will focus on exposure paths and influencing variables being evaluated by results of the data from environmental questionnaires.

Serum Dioxin-like Activity Is Associated with Reproductive Parameters in Young Men from the General Flemish Population

Background2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and some related environmental contaminants are aryl hydrocarbon receptor (AhR) ligands that exert reproductive and developmental toxicity in laboratory animals. In humans, fertility-related effects are less documented.ObjectiveThe aim of this study was to investigate the relationship between dioxin-like biological activity in serum and parameters of reproductive status in men from the general population 5 months after a polychlorinated biphenyl and dioxin food-contamination episode in Belgium.DesignIn the framework of the cross-sectional Flemish Environment and Health Study (FLEHS), we recruited 101 men 20–40 years of age and evaluated sperm parameters, measured sex hormones, and gathered information on a number of lifestyle factors. In addition, we determined the AhR-mediated enzymatic response elicited by individual serum samples and expressed it as TCDD equivalent concentrations (CALUX-TEQs) using an established transactivation assay.ResultsAge (p = 0.04) and the frequency of fish (p = 0.02) and egg (p = 0.001) consumption were independent positive determinants of serum dioxin-like activity. After correcting for possible confounders, we found that a 2-fold increase in CALUX-TEQ > 16 pg/L was associated with a 7.1% and 6.8% (both p = 0.04) decrease in total and free testosterone, respectively. We also observed a more pronounced drop in semen volume of 16.0% (p = 0.03), whereas sperm concentration rose by 25.2% (p = 0.07). No relationship was found with total sperm count or sperm morphology.ConclusionsThese data suggest an interaction of dioxin-like compounds with the secretory function of the seminal vesicles or prostate, possibly indirectly through an effect on testosterone secretion, at levels not affecting spermatogenesis as such.

Role of Secondary Alcohol Metabolites in Anthracycline Cardiotoxicity: from Hypotheses to New Drugs

The clinical use of doxorubicin and other anticancer anthracyclines is limited by the possible development of a life-threatening form of cardiomyopathy. Here, we briefly review biochemical and pharmacological studies that identify secondary alcohol metabolites as important mediators of cardiotoxicity induced by anthracyclines. The pharmacokinetics and pharmacodynamics of secondary alcohol metabolites suggest that they might cause cardiotoxicity while not mediating or actually diminishing the antitumour potency of anthracyclines. This concept implies that novel anthracyclines forming fewer amounts of their secondary alcohol metabolites might prove to spare the vulnerable cardiomyocytes while also retaining good activity in cancer cells, thus offering advantages over currently available anthracyclines in terms of therapeutic index. MEN 10755 (sabarubicin) is a newly designed disaccharide anthracycline that fits well in this context: it forms less alcohol metabolite than doxorubicin, and consistently induces less cardiac toxicity in laboratory animals in the face of an equal or even improved spectrum of activity in human tumour xenografts. On the basis of these preclinical findings, MEN 10755 has entered clinical trials, which will define its activity and safety and will serve an opportunity to probe the "secondary alcohol metabolite hypothesis" of cardiotoxicity. Keywords: anthracyclines, cardiotoxicity, secondary alcohol metabolites, iron, men, drug discovery

Early Developmental 2,3,7,8-Tetrachlorodibenzo-p-Dioxin Exposure Decreases Chick Embryo Heart Chronotropic Response to Isoproterenol but Not to Agents Affecting Signals Downstream of the Beta-Adrenergic Receptor

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) causes cardiovascular toxicity in laboratory animals, including alteration in several processes in which beta-adrenergic receptor (beta-AR) signaling plays important roles. Thus, our laboratory investigated the effects of TCDD on beta-AR expression and signal transduction. Fertile chicken eggs were injected with vehicle (corn oil), 0.24 or 0.3 pmol TCDD/g egg on incubation day 0 (D0) or D5. On D10, heart function was assessed by ECG in ovo. Exposure to TCDD increased the incidence of arrhythmias and decreased the positive chronotropic responsiveness of the heart to isoproterenol. The reduced beta-AR responsiveness was, in part, independent of any overt morphological changes in the heart as chick embryos exposed to TCDD on D5 displayed an intermediate responsiveness to beta-AR agonist in the absence of the dilated cardiomyopathy observed in chick embryos exposed to TCDD on D0. TCDD did not decrease the chronotropic response of the heart to agents that stimulate signals downstream of the beta-AR. In fact, TCDD-exposed embryos were more sensitive than controls to forskolin, increasing heart rates (HR) 21.8 +/- 3.5 beats per min (bpm) above baseline versus control values at 6.3 +/- 2.7 bpm above baseline. TCDD exposure also augmented the negative chronotropic response of the heart to verapamil, decreasing HR -23.2 +/- 7.4 bpm relative to baseline versus control embryos at -12.7 +/- 5.9 bpm below baseline. Finally, the mean cardiac beta1-AR mRNA expression in D10 embryos was not significantly altered by exposure to TCDD on D0. These findings establish that a functional end point of the developing chick heart is sensitive to TCDD exposure and that the TCDD-induced reduction in beta-AR responsiveness may result from alterations in signal transduction upstream of adenylyl cyclase.

Pediatric exposure and potential toxicity of phthalate plasticizers.

Phthalates are plasticizers that are added to polyvinyl chloride (PVC) products to impart flexibility and durability. They are produced in high volume and generate extensive though poorly defined human exposures and unique childhood exposures. Phthalates are animal carcinogens and can cause fetal death, malformations, and reproductive toxicity in laboratory animals. Toxicity profiles and potency vary by specific phthalate. The extent of these toxicities and their applicability to humans remains incompletely characterized and controversial. Two phthalates, diethylhexyl phthalate (DEHP) and diisononyl phthalate (DINP), have received considerable attention recently because of specific concerns about pediatric exposures. Like all phthalates, DEHP and DINP are ubiquitous contaminants in food, indoor air, soils, and sediments. DEHP is used in toys and medical devices. DINP is a major plasticizer used in children's toys. Scientific panels, advocacy groups, and industry groups have analyzed the literature on DEHP and DINP and have come to different conclusions about their safety. The controversy exists because risk to humans must be extrapolated from animal data that demonstrate differences in toxicity by species, route of exposure, and age at exposure and because of persistent uncertainties in human exposure data. This report addresses sensitive endpoints of reproductive and developmental toxicity and the unique aspects of pediatric exposures to phthalates that generate concern. DEHP and DINP are used as specific examples to illustrate the controversy.

Phthalate Exposure and Human Semen Parameters

There is scientific and public concern about commonly used chemicals, including phthalates, that are associated with reproductive toxicity in laboratory animals and are hormonally active. People are exposed to phthalates through diet, consumer products and medical devices. The present study explored whether environmental levels of phthalates are associated with altered semen quality in humans. We recruited 168 men who were part of subfertile couples and who presented to the Massachusetts General Hospital andrology laboratory for semen analysis between January 2000 and April 2001. Semen parameters were dichotomized based on 1999 World Health Organization reference values for sperm concentration (< 20 million/ml) and motility (< 50% motile), as well as Tygerberg Strict criteria for morphology (< 4% normal). The comparison group was men for whom these semen parameters were all above the reference values. In urine, eight phthalate metabolites were measured with high-performance liquid chromatography and tandem mass spectrometry. Specific gravity-adjusted phthalate metabolite levels were categorized into tertiles. There was a dose-response relation between tertiles of mono-butyl phthalate and sperm motility (odds ratio per tertile = 1.0, 1.8, 3.0; P-value for trend = 0.02) and sperm concentration (1.0, 1.4, 3.3; P-value for trend = 0.07). In addition, there was a dose-response relation between tertiles of mono-benzyl phthalate and sperm concentration (1.0, 1.4, 5.5; P-value for trend = 0.02). There were dose-response relations for monobutyl phthalate and monobenzyl phthalate with one or more semen parameters, and suggestive evidence for monomethyl phthalate with sperm morphology. The lack of a relation for other phthalates may indicate a difference in spermatotoxicity among phthalates.

Low dose exposure to cadmium and its health effects. (3) Toxicity in laboratory animals and cultured cells

We have reviewed studies on cadmium (Cd) toxicity in laboratory animals and cultured cells with special attention to the disruption in cellular signal transduction, involvement in apoptosis of Cd, the cellular transport system for Cd and roles of metallothionein as a protective factor against Cd. Cd affects cellular functions by perturbing signal transductions, such as protein kinase C, mitogen-activated protein kinase and cyclic AMP pathways, but how the disruption of these pathways by Cd leads to the manifestation of toxicity in vivo is largely unknown. Exposure to cadmium at relatively high and low levels causes necrosis and apoptosis, respectively, which suggests that the mode of cell death by cadmium is dependent upon its exposure level. On the other hand, utilization of Ca2+ channels, DMT1 (divalent metal transporter 1) and a novel transport system having high-affinity for Mn2+ and Cd2+ were found to act as Cd transport systems via the cellular membrane. Metallothionein-I/II-null mice are highly susceptible to renal toxicity, hepatotoxicity, bone injury, hematotoxicity and immunotoxicity caused by chronic Cd exposure. Thus, metallothionein plays an important role in detoxification of Cd toxicity.

Characterization of F-actin depolymerization as a major toxic event induced by pectenotoxin-6 in neuroblastoma cells

Pectenotoxins are a group of marine toxins produced by dinoflagellates and formerly included within the group of diarrhetic shellfish poison or toxins (DSP or DST) because of their physico-chemical properties. However, toxicological data on pectenotoxins are still very scarce and its mechanism of action is largely unknown, but toxicity in laboratory animals has been demonstrated by intraperitoneal injection. In this report, we present results of in vitro toxicological assessment of pectenotoxin-6, a derivative of the parental toxin pectenotoxin-2 first isolated from toxic scallops. Results obtained demonstrate an specific time- and dose-dependent depolymerization of F-actin in neuroblastoma cells exposed to pectenotoxin-6 (half-maximal effect about 700 nM at 24 hr). The change in the state of polymerization of actin was not accompanied by other major effects on specific signal transduction pathways or cell survival rate. Pectenotoxin-6 does not modify cytosolic calcium levels either in a calcium containing or calcium-free medium in human lymphocytes. Only when capacitative calcium influx was first activated, the toxin addition significantly decreased the following calcium influx. In these cells, pectenotoxin-6 only modifies cAMP (adenosine 3′,5′-cyclic monophosphate) levels in calcium-free conditions. In addition, no effect on cell attachment or apoptosis induction was observed at micromolar concentrations of pectenotoxin-6. Therefore, we conclude that cytoskeletal disruption is a key mechanism of PTX6-induced toxicity in eukaryotic cells.

The History of Thalidomide.

The first paper describing the pharmacological actions of thalidomide was published in 1956. The drug, then designated as K17, was thought to have sedative effects superior to those of comparator drugs and was thought to be virtually nontoxic. Only 2 years after thalidomide's launch as Contergan in Germany, it's alleged lack of toxicity came into question, with reports of the drug causing numerous side effects. Shortly thereafter, thalidomide was connected with an epidemic of horrific deformities in children whose mothers had taken the drug during pregnancy. This disaster brought on by thalidomide's teratogenic effects was responsible for the institution of some regulatory bodies, such as the United Kingdom's Committee on the Safety of Drugs, and for the strengthening of others, such as the U.S. Food and Drug Administration. An objective examination of published papers and contemporary accounts confirms that the preclinical tests on thalidomide were superficial, and there is no doubt that it was never administered to pregnant animals prior to its use in patients. Within a short time after its withdrawal from the market due to its suspected association with fetal abnormalities, the drug was shown to produce fetal toxicity in laboratory animals. Had there been more extensive testing on laboratory animals before the drug was launched, the disaster could have been avoided. (c) 2002 Prous Science. All rights reserved.

Quantitative evaluation of alternative mechanisms of blood disposition of di(n-butyl) phthalate and mono(n-butyl) phthalate in rats.

Phthalate esters are ubiquitous, low-level environmental contaminants that induce testicular toxicity in laboratory animals. The diester is rapidly metabolized in the gut to the monoester, which causes the testicular toxicity. Several physiologically based pharmacokinetic (PBPK) model structures have been evaluated for di(2-ethylhexyl) phthalate (DEHP) and mono(2-ethylhexyl) phthalate (MEHP). The objective of this study was to test these PBPK models for a less lipophilic phthalate diester, di(n-butyl) phthalate (DBP), and monoester, mono(n-butyl) phthalate (MBP). Alternate models describing enterohepatic circulation, diffusion-limitation, tissue pH gradients (pH trapping), and a simpler, flow-limited model were evaluated. A combined diffusion-limited and pH trapping model was also tested. MBP tissue:blood partition coefficients were similar when determined either experimentally by a nonvolatile, vial equilibration technique or algorithmically. All other parameters were obtained from the literature or estimated from MBP blood concentrations following intravenous or oral exposure to DBP or MBP. A flow-limited model was unable to predict MBP blood levels, whereas each alternative model had statistically better predictions. The combined diffusion-limited and pH trapping model was the best overall, having the highest log-likelihood function value. This result is consistent with a previous finding that the pH trapping model was the best model for describing DEHP and MEHP blood dosimetry, though it was necessary to extend the model to include diffusion-limitation. The application of the pH trapping model is a step toward developing a generic model structure for all phthalate esters, though more work is required before a generic structure can be identified with confidence. Development of a PBPK model structure applicable to all phthalate esters would support more realistic assessments of risk to human health from exposure to one or more members of this class of compounds.