National Toxicology Program

Selected toxicity information from HSDB, one of the National Library of Medicine's databases. ¹

Names (NTP)

• 2,4-OXAZOLIDINEDIONE, 3-(3,5-DICHLOROPHENYL)-5-ETHENYL-5-METHYL-
• 2,4-OXAZOLIDINEDIONE, 3-(3,5-DICHLOROPHENYL)-5-ETHENYL-5-METHYL-
• VINCLOZOLIN (ENDOCRINE DISRUPTOR)
• VINCLOZOLIN PUBERTAL STUDY
• VORLAN
• VORLAN
• Endocrine disruptor (Vinclozolin)
• Pubertal vinclozolin study
• Vinclozolin

Human Toxicity Excerpts

• Low toxicity by ingestion and inhalation. [Lewis, R.J. Sax's Dangerous Properties of Industrial Materials. 9th ed. Volumes 1-3. New York, NY: Van Nostrand Reinhold, 1996., p. 2883]**PEER REVIEWED**
  
• Industrial-derived endocrine disruptors or endocrine-active chemicals (EACs) have been identified and hypothesized to play a role in human disease. Most of the xeno-endocrine-active chemicals which have been characterized bind to the estrogen receptor, aryl hydrocarbon, or androgen receptor. Hazard and risk assessment of xeno-endocrine-active chemicals is complicated by several factors which include the following: (i) humans are exposed to relatively high levels of natural endocrine-active chemicals compared to xenoendocrine-active chemicals; (ii) very little information on the effects of metabolism, serum, and intracellular binding proteins on target cell uptake of endocrine-active chemicals is known; (iii) humans are exposed to endocrine-active chemical mixtures and their interactive effects may be additive, antagonistic, or synergistic and also response- and tissue-specific; and (iv) individual endocrine-active chemicals may be agonists/antagonists for more than one endocrine response pathway. Scientific-based hazard and risk assessment of both natural and xeno-endocrine-active chemicals clearly requires more information on dietary intakes, target organ exposures, mechanisms of action, and interactive effects of mixtures. [Safe S et al; Regulatory Toxicology and Pharmacology 26 (1 part 1): 52-58 (1997)]**PEER REVIEWED**
  
• P-glycoprotein (P-gp) is a 170 kDa membrane-bound glycoprotein shown to efflux a wide variety of chemicals, such as chemotherapeutic agents and carcinogens. Experiments were conducted using B16/F10 murine melanoma cells transfected with the human MDR1 gene (B16/hMDR1 cells), which codes for P-glycoprotein, to determine whether this transporter may contribute to the cellular efflux of some pesticides. Thirty-eight pesticides representing several classes of compounds were evaluated for their potential to bind to P-glycoprotein, as measured by the inhibition of efflux of the P-glycoprotein substrate doxorubicin. Carbamate and pyrethroid insecticides exhibited little interaction with P-glycoprotein, while many of the organophosphorus and organochlorine pesticides significantly inhibited the efflux of doxorubicin. Pesticides that significantly inhibited the efflux of doxorubicin were then assessed for P-glycoprotein-mediated efflux. One pesticide, endosulfan, exhibited slight though significant transport mediated by P-glycoprotein. Competition experiments performed with the P-glycoprotein ligand (3H)azidopine demonstrated that the P-glycoprotein inhibitory pesticides bound to P-glycoprotein. Both lipophilicity and molecular mass were major physical/chemical determinants in dictating pesticide binding to P-glycoprotein, with optimum binding occurring with compounds having a log Kow value of 3.6-4.5 and a molecular weight of 391-490 Da. The transport substrate endosulfan possessed optimal binding characteristics. These results demonstrated that many pesticides are capable of binding to P-glycoprotein; however, binding does not infer transport. [Bain LJ and GA Leblanc; Toxicology and Applied Pharmacology 141 (1): 288-298 (1996)]**PEER REVIEWED**
  
• Objectives--To examine internal exposure and targeted health outcomes of employees exposed to 3-(3,5-dichlorophenyl)-5-methyl-5-vinyl-1,3-oxazolidine-2,4-dione; chemical abstracts service (CAS) number: 50471-44-8 (vinclozolin). Methods--A cross sectional study of 67 men exposed to vinclozolin for 1-13 years during synthesis and formulation operations and 52 controls. Biomonitoring was based on determination of urinary metabolites that contained a 3,5-dichloroaniline (3,5-DCA) moiety. Targeted health endpoints were the same as in previous subchronic and chronic animal studies--namely, reversible changes in the concentrations of hormones of the adrenocorticotrophic and gonadotrophic feedback systems, signs of liver injury, hemolytic anemia, cataract formation (uniquely in rats), and hormonally induced hyperplasia and tumors at high doses. The clinical investigation consisted of a medical and occupational history questionnaire, physical examination, laboratory determinations (including testosterone, LH, and FSH measurements), ultrasonography of the liver and prostate, a detailed eye examination, and routine spirometry. Results--The mean 3,5-dichloroaniline concentration for two thirds of the study group exceeded an equivalent of the vinclozolin acceptable daily intake (ADI) used for consumer regulatory purposes. Even the highest concentrations were, however, at least 10 times below the no observable adverse effect level (NOAEL) based on animal studies. Analysis of physical examination and laboratory data provided no evidence of hormonal responses induced by vinclozolin. Furthermore, no evidence of liver injury, prostate changes, cataract formation, or hemolytic anemia was found. Conclusion--There was no evidence of any health effects induced by vinclozolin among employees with potential long term exposure. In particular, no antiandrogenic effects were found. [Zober A et al; Occup Environ Med 52 (4): 233-41 (1995)]**PEER REVIEWED**
  

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Non-Human Toxicity Excerpts

• Treatment of actively growing Botrytis cinerea hyphae with micromolar concentrations of the dicarboximide fungicide vinclozolin resulted in significant alterations in the growth rate, morphology, and chemical composition of the cells. The addition of vinclozolin resulted in an immediate and severe reduction in the hyphal growth rate and a retardation in the emergence of the second germ tube. Cells treated with vinclozolin had a lower content of pool metabolites than control cells, and this difference increased with time of exposure to the fungicide. In contrast, vinclozolin-treated cells had a higher chitin concentration than control cells. These biochemical alterations were followed by the disorganization and clearing of cells, and by the appearance of dense and dark masses outside the hyphae, presumably composed of cell debris. Hyphae exposed to vinclozolin were more curved and branched and had shorter cells than the controls. The results indicate that vinclozolin causes a slow but generalized leakage of pool metabolites; this release precedes cell lysis and is not the result of a rapid and gross damage to the cytoplasmic membrane. [Cabral S M J CS and J PS Cabral; Canadian Journal of Microbiology 43 (6): 552-560 (1997)]**PEER REVIEWED**
  
• Leydig cell adenomas are observed frequently in studies evaluating the chronic toxicity of chemical agents in laboratory animals. Doubts have been raised about the agents in laboratory animals. Doubts have been raised about the relevance of such responses for human risk assessment, but the question of relevance has not been evaluated and presented in a comprehensive manner by a broad group of experts. This article reports the consensus conclusions from a workshop on rodent Leydig cell adenomas and human relevance. Five aspects of Leydig cell biology and toxicology were discussed: 1) control of Leydig cell proliferation; 2) mechanisms of toxicant-induced Leydig cell hyperplasia and tumorigenesis; 3) pathology of Leydig cell adenomas; 4) epidemiology of Leydig cell adenomas; 5) risk assessment for Leydig cell tumorigens. important research needs also were identified. Uncertainty exists about the true incidence of Leydig cell adenomas in men, although apparent incidence is rare and restricted primarily to white males. Also, surveillance databases for specific therapeutic agents as well as nicotine and lactose that have induced Leydig cell hyperplasia or adenoma in test species have detected no increased incidence in humans. Because uncertainties exist about the true incidence in humans, induction of Leydig cell adenomas in test species may be of concern under some conditions. Occurrence of Leydig cell hyperplasia alone in test species after lifetime exposure to a chemical does not constitute a cause for concern in a risk assessment for carcinogenic potential, but early occurrence may indicate a need for additional testing. Occurrence of Leydig cell adenomas in test species is of potential concern as both a carcinogenic and reproductive effect if the mode of induction and potential exposures cannot be ruled out as relevant for humans. The workgroup focused on seven hormonal modes of induction of which two, GnRH agonism and dopamine agonism, were considered not relevant to humans. Androgen receptor antagonism, 5alpha-reductase inhibition, testosterone biosynthesis inhibition, aromatase inhibition, and estrogen agonism were considered to be relevant or potentially relevant, but quantitative differences may exist across species, with rodents being more sensitive. A margin of exposure (MOE; the ratio of the lowest exposure associated with toxicity to the human exposure level) approach should be used for compounds causing Leydig cell adenoma by a hormonal mode that is relevant to humans. For agents that a positive for mutagenicity, the decision regarding a margin of exposure or linear extrapolation approach should be made on a case-by-case basis. In the absence of information about mode of induction, it is necessary to utilize default assumptions, including linear behavior below the observable range. All of the evidence should be weighed in the decision-making process. [Clegg ED et al; Reproductive Toxicology 11 (1): 107-121 (1997)]**PEER REVIEWED**
  
• Many environmental contaminants alter the reproduction of animals by altering the development and function of the endocrine system. The ability of environmental contaminants to alter the endocrine system of alligators was studied both in a descriptive study in which juvenile alligators from a historically contaminated lake were compared to animals from a control lake and in an experimental study in which hatchling control alligators were exposed in ovo to several endocrine-disrupting standards and two modern-use herbicides. Endocrine status was assessed by examining plasma hormone concentrations, gonadal-adrenal mesonephros (GAM) aromatase activity, and gonadal histopathology. In the descriptive study, juvenile alligators from the contaminated lake had significantly lower plasma testosterone concentrations (29.2 pg/ml compared to 51.3 pg/ml), whereas plasma 17beta-estradiol concentrations did not vary when compared to controls. Gonadal-adrenal mesonephros aromatase activity was significantly decreased in the alligators from the contaminated lake (7.6 pmol/g/hr compared to 11.4 pmol/g/hr). In the experimental study, the endocrine-(disrupting standards had the expected effects. 17-beta-Estradiol and tamoxifen caused sex reversal from male to female, with a corresponding increase in aromatase activity. Vinclozolin had no apparent effect on male or female alligators. Among the herbicides tested, atrazine induced gonadal-adrenal mesonephros aromatase activity in male hatchling alligators that was neither characteristic of male nor females, although testiculate differentiation was not altered. Exposure to 2,4-dichlorophenoxyacetic acid had no effect on the endocrine parameters that were measured. Together, these studies show that exposure to some environmental chemicals (such as atrazine) can alter steroidogenesis in alligators, but the endocrine alterations previously noted for Lake Apopka, Florida, alligators can not be fully explained by this mechanism. [Crain DA et al; Environmental Health Perspectives 105 (5): 528-533 (1997)]**PEER REVIEWED**
  
• The efficacy of spraying with the fungicides iprodione and vinclozolin against storage rots of carrots was tested in 14 field trials. Despite having a larger amount of non-infected leaves, root samples from treated plots did not have significantly higher amounts of non-infected roots after longtime storage. The major damage was caused by Rhizoctonia carotae, a pathogen which was not affected by the fungicide treatments. Sclerotinia sclerotiorum was the pathogen most affected by the treatments. Arothecium carotae, formerly not registered in Sweden, was identified in two of the trials. Neither this pathogen nor others such as Mycocentrospora acerna and Botrytis cinerea were affected by the fungicide treatments. [Ewaldz T; Vaxtskyddsnotiser 61 (1): 8-13 (1997)]**PEER REVIEWED**
  
• The human progesterone receptor (hPR) B-form and a progesterone-sensitive reported were expressed in yeast and used to screen a library of synthetic chemicals for their ability to function as agonists or antagonists of human progesterone receptor. The transcriptional activity of human progesterone receptor was not increased in the presence of over 40 individual chemicals. Seven chemicals decreased progesterone-dependent activity in yeast. The most effective chemicals were 6-hydroxychrysene, 1-hydroxypyrene, 4-hydroxy, 2', 4', 6'-trichloro biphenyl, and 4-hydroxy, 2', 3', 4', 5',tetrachloro biphenyl. The decrease of progesterone-mediated transactivation strongly correlated with their displacement of (3H)progesterone from human progesterone receptor. The absence of the hydroxyl group on the above chemicals completely abolished their inhibitory activity. The other chemicals which decreased progesterone activity were endosulfan II, endosulfan sulfate, and lindane. These chemicals did not inhibit (3H)progesterone binding, suggesting that they inhibit progesterone action by interacting with a region of human progesterone receptor distinct from binding (3H)progesterone or by a mechanism independent of human progesterone receptor. These results highlight the utility of yeast for screening hormonally-active chemicals. In addition, hydroxylation appears to be essential for the interaction of some chemicals with human progesterone receptor. [Jin L et al; Biochemical and Biophysical Research Communications 233 (1): 139-146 (1997)]**PEER REVIEWED**
  
• Vinclozolin and p,p'-DDE induced antiandrogenic developmental effects in vivo and are potent inhibitors of androgen receptor (AR) binding and androgen receptor-dependent gene expression in vitro. To determine whether this molecular mechanism is operative in vivo, the effects of these compounds on two androgen-regulated prostatic mRNAs were studied. Rats were sham operated or castrated and immediately implanted with one or two empty 2.5-cm silastic capsules or with on e(1) or two (2) 2.5-cm capsules containing testosterone (T). T-implanted rats were treated by gavage for 4 days with vehicle (corn oil), vinclozolin (200 mg/kg/day), p,p'-DDE (200 mg/kg/day), or the antiandrogen flutamide (100 mg/kg/day) as a positive control. Vinclozolin, p,p'-DDE, and flutamide all induced a reciprocal decline in seminal vesicle (p < 0.01) and prostate ( p < 0.01) weight as well as a reduction in immunohistochemical staining of androgen receptor in epididymal nuclei compared to vehicle-treated T-implanted controls. Specific androgen receptor antagonism was assessed by determining the ability of these chemicals to induced a testosterone-repressed prostatic message (i.e., TRPM-2) and/or repress a testosterone-induced prostatic message (i.e. prostatein subunit C3). Densitometry scans of Northern blots indicated that vinclozolin, p,p'-DDE, and flutamide each induced TRPM-2 mRNA and repressed C3 mRNA compared to vehicle-treated T-implanted controls. These antiandrogenic effects were competitively reduced in castrate rats implanted with two 2.5 cm T capsules (2). where serum T levels were elevated more than twofold above physiological levels. Taken together, these data indicate that vinclozolin and p,p'-DDE act as antiandrogens in vivo by altering the expression of androgen-dependent genes. [Kelce WR et al; Toxicology and Applied Pharmacology 142 (1): 192-200 (1997)]**PEER REVIEWED**
  
• Industrial chemicals and environmental pollutants can disrupt reproductive development in wildlife and humans by mimicking or inhibiting the action of the gonadal steroid hormones, estradiol and testosterone. The toxicity of these so-called environmental endocrine disruptors is especially insidious during sex differentiation and development due to the crucial role of gonadal steroid hormones in regulating these processes. This review describes the mechanism of toxicity and clinical implications of a new class of environmental chemicals that inhibit androgen-mediated sex development. For several of these chemicals, including the agricultural fungicide vinclozolin and the ubiquitous and persistent 1,1,1-trichloro-2,2-bis (p-chlorophenyl)ethane metabolite 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene, the molecular mechanism of action and the adverse developmental effects on male sex differentiation have been elucidated and are used as examples. Environmental chemicals with antiandrogenic activity offer profound implications with regard to recent clinical observations that suggest an increasing incidence of human male genital tract malformations, male infertility, and female breast cancer. Finally, in light of increasing concern over the potential endocrine disrupting effects of environmental pollutants, an in vitro/in vivo investigational strategy is presented which has proved useful in identifying chemicals with antiandrogen activity and their mechanism of action. [Kelce WR and EM Wilson; Journal of Molecular Medicine 75 (3): 198-207 (1997)]**PEER REVIEWED**
  
• Many pesticides are known to produce reproductive and developmental effects in chronically-exposed non-target organisms, including humans. Recent evidence suggests that demasculinization may be an important mechanism responsible for some of these effects. Some pesticides have been shown to interact with the androgen receptor and to act as antagonists, while others have been shown to interact with the estrogen receptor and function as estrogens both in vitro and in vivo. Many pesticides can also lower serum androgen levels by altering rates of synthesis or metabolism. Given the ubiquity of pesticides in the environment and the multiple mechanisms whereby they can elicit demasculinizing effects, synergy between such compounds may produce clinical endocrine dysfunction at current human exposure levels. [Leblanc GA et al; Molecular and Cellular Endocrinology 126 (1): 1-5 (1997)]**PEER REVIEWED**
  
• Oxidative damage was quantified in the liver of rats by measuring the levels of 8-OH-2-deoxyguanosine (8-OH-2DG) relative to 2-deoxyguanosine in DNA after treating rats for 10 days at a total dose of 1 mg/kg/day with a mixture of the 15 pesticides most commonly found in Italian foods (comprised of dithiocarbamate, benomyl, procymidone, methidathion, chlorpyrifos-ethyl, parathion-methyl, chlorpropham, parathion, vinclozolin, chlorfenvinphos, pirimiphos ethyl, thiabendazole, fenarimol, diphenylamine and chlorothalonil). We fractionated this pesticide mixture into subgroups in order to determine which molecules, if any, induced DNA oxidative damage. The administration of diphenylamine (0.09-1.4 mg/kg/day) and chlorothalonil (0.13-1 mg/kg/day) induced a dose-dependent increase in 8-OH-2-deoxyguanosine levels in liver DNA. The other 13 pesticides of the mixture on the contrary, did not produce oxidative liver DNA damage. These results indicate that the toxicity of low doses of pesticide mixtures present in food might be further reduced by eliminating diphenylamine and chlorothalonil. [Lodovici M et al; Toxicology 117 (1): 55-60 (1997)]**PEER REVIEWED**
  
• This study was conducted to determine the effect of herbicides registered for use on seedling alfalfa (Medicago sativa) on mycelial growth, sclerotium production and subsequent carpogenic germination, and ascospore germination of Sclerotinia trifoliorum. One or more growth or developmental stages of S. trifoliorum were affected by each herbicide tested. Mycelial growth and sclerotium production were completely inhibited by pronamide at 10 mug active ingredient (ai) per ml. Pronamide had no effect on ascospore germination at concentrations up to 100 mug ai/ml but reduced ascospore germ tube length at 1 mug ai/ml. Mycelial growth was reduced by 2,4-DB at 1 mug ai/ml. Mycelial growth, sclerotium production, and ascospore germination were completely inhibited by 2,4-DB at 100 mug ai/ml. Bromoxynil reduced mycelial growth at 10 mug ai/ml, and reduced sclerotium weight, ascospore germination, and germ tube length at 100 mug ai/ml. Mycelial growth and sclerotium production were completely inhibited by bromoxynil at 1000 mug ai/ml. Sethoxydim reduced mycelial growth at 10 mug ai/ml, and sclerotium weight at 1000 mug ai/ml. Imazethapyr reduced mycelial growth at 1000 mug ai/ml, had no effect on sclerotium weight and ascospore germination, but enhanced carpogenic germination at 100 mug ai/ml. The fungicide vinclozolin was more toxic to S. trifoliorum than any of the herbicides tested, in that it completely inhibited mycelial growth and ascospore germination at 1 mug ai/ml. [Reichad SL et al; Mycologia 89 (1): 82-88 (1997)]**PEER REVIEWED**
  
• A bioassay system for rapid detection of carcinogenic agents has been developed using male Fischer 344 rats to bridge the gap between long-term carcinogenicity tests and short-term screening assays. The system, called the medium-term liver bioassay, is fundamentally based on the 2-stage hypothesis of tumor production, employing initiation by diethylnitrosamine (200 mg/kg, ip) in the first stage and test chemical administration during the second, in combination with two-thirds partial hepatectomy. It requires only 8 wk for animal experimentation and a further few weeks for quantitative analysis of immunohistochemically demonstrated glutathione S-transferase placental form positive hepatic foci. A total of 291 chemicals/substances have already been analyzed in our laboratory. Among 63 chemicals that were proved to be carcinogenic in the liver of rat and/or mouse, 57 (90%) gave positive results irrespective of their mutagenicity. Negative compounds include peroxisome proliferators and tamoxifen. Even nonhepatocarcinogens were positive at a rate of 24%. Eighty-six percent (12/14) of mouse liver carcinogens were also positive. On the other hand, only 2 out of 45 noncarcinogens showed very weak positivity. Thus, the efficacy of the system for hepatocarcinogens has been well established. This bioassay is increasingly regarded as an appropriate alternative test for carcinogenicity risk assessment and is practically used for a rapid evaluation of hepatocarcinogenicity of chemicals. [Shirai T; Toxicologic Pathology 25 (5): 453-460 (1997)]**PEER REVIEWED**
  
• A dicarboximide-susceptible (DS) isolate and a dicarboximide-resistant (DR) isolate of Botrytis cinerea were compared with regard to spore germination, mycelial growth, cellular leakage, and lipid peroxidation upon treatment with the dicarboximide fungicide vinclozolin. The fungicide inhibited spore germination and mycelial growth of the dicarboximide-susceptible isolate, but not those of the dicarboximide-resistant isolate. The inhibitory effect of the fungicide was greater on mycelial growth than on spore germination of the dicarboximide-susceptible isolate. Significant cellular leakage from the fungicide-treated dicarboximide-susceptible or dicarboximide-resistant isolate began to increase after 24 hr incubation, depending on the concentration of the fungicide and the duration of incubation time. However, the magnitude of cellular leakage was much greater from the dicarboximide-susceptible isolate than from the dicarboximide-resistant isolate. Vinclozolin caused considerable lipid peroxidation in the dicarboximide-susceptible isolate, whereas little or no lipid peroxidation occurred in the dicarboximide-resistant isolate treated with the fungicide. Lipid peroxidation preceded cellular leakage from the dicarboximide-susceptible isolate following fungicide treatment. The effects of the fungicide on mycelial growth, cellular leakage, and lipid peroxidation of the dicarboximide-susceptible isolate were all reversed by the addition of alpha-tocopherol to the incubation medium. These results demonstrate that vinclozolin causes significant lipid peroxidation and subsequent cellular leakage from a dicarboximide-susceptible isolate, but not from a dicarboximide-resistant isolate. Furthermore, they suggest that the mechanism of action of dicarboximide fungicides is associated with membrane lipid peroxidation. [Choi GJ et al; Pesticide Biochemistry and Physiology 55 (1): 29-39 (1996)]**PEER REVIEWED**
  
• The mutagenic/cocarcinogenic potential of the fungicide vinclozolin was assessed by a comprehensive examination of toxicity mechanisms at both the genetic and the metabolic level. Vinclozolin did not induce any significant increase in chromosomal aberrations in human peripheral blood lymphocytes cultures in vitro, both in the presence and in the absence of metabolic activation. However, significant dose-related increases in micronucleated erythrocytes (up to 4-fold over the control) were found in the bone marrow cells of mice 24 hr after treatment with the fungicide over a range of concentrations from 312.5 to 1250 mg/kg. The morphology and the size of micronuclei induced was suggestive of a predominantly clastogenic mode of action. Several cytochrome P450 (CYP)-dependent reactions have been monitored in liver, kidney and lung microsomes of male and female Swiss Albino CD1 mice in order to ascertain certain toxic non-genetic properties (related to carcinogenesis) of vinclozolin. It was found to be a selective inducer towards cytochrome P450 3A (liver, kidney) and 2E1 (liver), as exemplified by the significant increases of the demethylation of aminopyrine (APND, up to 2.3-fold, female liver), and hydroxylation of p-nitrophenol (pNPH, up to 5.6-fold, male liver). In general, however, vinclozolin has a complex pattern of induction and suppression of cytochrome P450-dependent enzymes, as shown from the reduced expression of various monooxygenases depending upon dose, sex or organ considered. For example, pNPH activity was suppressed in kidney (up to 48% loss, averaged between male and female), whereas ethoxycoumarin O-deethylase was reduced in lung up to 53% in male (at the highest dose). These data were sustained by means of Western immunoblotting using rabbit polyclonal antibodies anti-cytochrome P450 3A and 2E1. Northern blotting analysis using cytochrome P450 3A1/2 and 2E1 cDNA biotinylated probes showed that the expression of such isozymes is regulated at the mRNA level. Taken together, the findings indicate the clastogenic activity and the possible cotoxic, cocarcinogenic and promoting potential of vinclozolin. [Hrelia P et al; Mutagenesis 11 (5): 445-53 (1996)]**PEER REVIEWED**
  
• Possible modifying effects of pesticide mixtures on tumorigenesis were investigated with medium-term carcinogenesis protocols for rapid detection of carcinogenic agents using male F344 rats. In the 8-wk liver model, administration of 20 pesticides (19 organophosphorus compounds and one organochlorine), added to the diet each at acceptable daily intake (ADI) levels, did not enhance rat liver preneoplastic lesion development initiated by diethyltyrosamine. In contrast, a mixture of these 20 pesticides at 100 times the acceptable daily intake significantly increased the number and area of liver lesions. In the second experiment using a multi-organ carcinogenicity protocol of 28 wk, mixtures of 40 pesticides (high production examples) or 20 pesticides (suspected carcinogens) added to the diet at their respective acceptable daily intake levels did not modulate carcinogenesis in any organ initiated by five known potent carcinogens in combination. These results thus provide direct support for the safety factor (usually 100) approach using acceptable daily intake values for the quantitative risk evaluation of pesticides. [Ito N et al; Food and Chemical Toxicology 34 (11-12): 1091-1096 (1996)]**PEER REVIEWED**
  
• Selected pesticides (aldicarb, 1,3-dichloropropene, methidathion, parathion, triadimefon, vinclozolin) were tested for their clastogenic and aneugenic activities in the mouse bone-marrow micronucleus (MN) test in vivo and for their sister-chromatid exchange-inducing activities in human lymphocytes in vitro in the presence and absence of an exogenous metabolizing system from rat-liver S9. 1,3-Dichloropropene significantly increased the frequencies of micronucleated polychromatic erythrocytes (PCE) in bone-marrow cells of female mice from 3.3 micronucleus/1000 polychromatic erythrocytes to 15.3 micronucleus/1000 polychromatic erythrocytes (187 mg/kg bw). 1,3-Dichloropropene (100 uM) induced 16.0 SCE/metaphase after 24 hr of incubation as compared with the basal rate of 11.2 SCE/metaphase (-S9) and of 15.4 SCE/metaphase as compared with 10.5 SCE/metaphase of the control (+S9). These values were statistically significantly different from each other. The other pesticides tested did neither increase the rate of micronuclei significantly in polychromatic erythrocytes in male nor in female animals. Aldicarb and methidathion induced a significant increase in SCEs in human lymphocytes in vitro only without the metabolic activating system: aldicarb, 5 uM, 24 hr incubation; 15.5 SCE/metaphase; control: 12.6 SCE/metaphase; methidathion, 100 uM, 24 hr incubation: 15.8 SCE/metaphase, control: 11.1 SCE/metaphase. Parathion, triadimefon and vinclozolin did not have any SCE-inducing effects. [Kevekordes S et al; Toxicol Lett 89 (1): 35-42 (1996)]**PEER REVIEWED**
  
• Vinclozolin, a dicarboximide fungicide, alters morphological sex differentiation in male rats following perinatal exposure. The occurrence of these abnormalities correlates with the in vivo formation of two antiandrogenic metabolites of vinclozolin, (i.e. 2-(((3,5-dichlorophenyl)-carbamoyl)oxy)-2-methyl-3-butenoic acid (M1) and 3',5'-dichloro-2-hydroxy-2-methylbut-3-enanilide (M2)), which are potent inhibitors of rat androgen receptor binding. As steroid hormone receptors exhibit promiscuity in their ability to bind different ligands, the present study evaluated the ability of these vinclozolin metabolites to bind to the estrogen (ER) and progesterone (PR) receptors in vitro, and to alter estrogen receptor and progesterone receptor function following in vivo exposure. To this end, in vitro ligand binding assays demonstrated that both 2-(((3,5-dichlorophenyl)-carbamoyl)oxy)-2-methyl-3-butenoic acid and 3',5'-dichloro-2-hydroxy-2-methylbut-3-enanilide can compete with endogenous ligand for binding to the progesterone receptor (Ki = 400 and 60 muM, respectively). In contrast, neither metabolite exhibited the ability to bind estrogen receptor. Subsequent in vivo studies to evaluate the potential of vinclozolin to alter estrogen receptor or progesterone receptor function demonstrate that, (1) the estrogen-dependent increases in uterine weight and progesterone receptor induction were not altered by vinclozolin; (2) the distribution of nuclear and cytosolic progesterone receptor was not altered following short-term vinclozolin exposure: and (3) vinclozolin did not disrupt ovulation in cycling female rats. These studies indicate that although vinclozolin metabolites can compete for binding to the progesterone receptor in vitro, concentrations of these metabolites do not reach sufficient levels to disrupt female reproductive function following short-term in vivo exposure to vinclozolin. in addition, these studies demonstrate the importance of correlating in vitro receptor binding data with in vivo studies in order to understand the physiological consequences of exposure to environmental toxicants. [Laws SC et al; Toxicology 112 (3): 173-182 (1996)]**PEER REVIEWED**
  
• Grey mould, incited by Botrytis cinerea, can cause serious damages on cyclamen in the presence of conditions highly favorable to the pathogen. Its control relies, beside the adoption of appropriate cultural techniques, on the application of chemicals. However, chemical control is complicated by the widespread presence of populations of B. cinerea resistant to benzimidazoles and dicarboximides. Several experimental trials have been carried out during the past 5 years in order to test the efficacy of different fungicides, chosen among those already available and some new ones at present under development. Among the already available fungicides, the mixtures of carbendazim + diethofencarb, procymidone + thiram and chlozolinate + thiram performed well in all trials. Among the new fungicides, fludioxonil, alone and in mixture with cyprodinil were highly effective. Also pyrimethanil provided good disease control. By considering the phytoxicity, among the tested fungicides and under our experimental conditions, only anilazine, chlorothalonil, fluazinam and tebuconazole caused unacceptable flower injury. [Minuto A et al; Mededelingen Faculteit Landbouwkundige en Toegepaste Biologische Wetenschappen Universiteit Gent 61 (2A): 453-459 (1996)]**PEER REVIEWED**
  
• In 1991, the effectiveness of fungicides iprodione (Rovral 50%), vinclozolin (Ronilan 50%), procymidone (Sumilex 50%), dichlofluanid (Euparen 50%) and folpet (Folpet 50%) in controlling grey mould on grapes was tested infield experiments. Fungicides were applied four times according to the phenological method. At harvest, the percentage of infection was evaluated. All fungicides gave a significant reduction in disease compared with the untreated control, but among them folpet showed a slightly inferior result. Unclarified musts were analyzed for fungicide residues. The residue contents were below the prescribed tolerance. The highest amounts of residues in must were found in the must that contained iprodione. There was no significant difference among other fungicide residue contents in must. The influence of fungicides on the fermentation of musts was monitored for 3 years. Fermentation was strongly influenced by folpet. Iprodione, vinclozolin, procymidone, and dichlofluanid showed no influence on fermentation. [Mlikota F et al; Journal of Wine Research 7 (2): 103-110 (1996)]**PEER REVIEWED**
  
• The larvae of green lacewing, Mallada basalis are polyphagous predators which have been mass-reared in the laboratory and released against two-spotted mites, Tetranychus urticae on strawberry in Taiwan. Toxicity of 23 commonly used insecticides used to control pests of strawberry were evaluated against larvae of M. basalis. The tested pesticide dosages were equivalent to those recommended in the field on strawberry and other crops. Pesticides diluted with acetone were first sprayed on glass plates to make a residue film on which 0-24 hour-old larva were placed. Mortality were recorded at 24, 48, 72 hr after application. Results revealed that 6 acaricides: hexythiazox, fenbutatin-oxide, oxythioquinox, fenpyroximate, fenothiocarb, abamectin and 9 fungicides: carbendazim, vinclozolin, mancozeb + metalaxyl, metiram + vinclozolin, iprodione, procymidone, carbendazim + metiram, prochlorate manganese, benomyl are harmless (mortality < 50%) to the larvae of M. basalis. Among the eight insecticides tested, carbofuran is harmful (mortality 100%); methomyl, chlorpyrifos, mevinphos, and permethrin are moderately harmful (mortality 80-99%); deltamethrin is slightly harmful (mortality 50-79%); fenvalerate and cypermethrin are harmless (mortality < 50%). The second stage of the test was conducted on strawberry in the pot maintained under field condition. Recommended concentration of pesticides diluted with water were sprayed onto the strawberry plants until it runs off. Ten pots of strawberry treated with each pesticide were kept on the field and covered with plastic transparency film to cut out rain. Strawberry leaves cut off from each pot 0, 1, 2, 4, 7, 14, 28 days after treatment were kept underside up on a pad of cotton wool placed in a plastic tray filled with water. One 0-24 hour-old larva of M. basalis was placed on each leaf and fed with eggs of Corcyra cephalonica. Mortality were recorded at 24, 48, 72 hours after treatment. The semi-field residual effect of 12 pesticides tested is rated in the order of chlorpyrifos, permethrin > methomyl/carbofuran > mevinphos, deltamethrin > fenvalerate > cypermethrin > abamectin > oxythioquinox, procymidone, iprodione. [Tzeng CC and SS Kao; Plant Protection Bulletin 38 (3): 203-213 (1996)]**PEER REVIEWED**
  
• The mechanism of antiandrogenic activity of vinclozolin (3-(3,5-dichlorophenyl)-5-methyl-5-vinyloxazolidine-2,4-dione), a dicarboximide fungicide under investigation for its potential adverse effects on human male reproduction, was investigated using recombinant human androgen receptor (AR). The two primary metabolites of vinclozolin in plants and mammals are M1 (2-[[3,5-dichlorophenyl)-carbamoyl]oxy]-2-methyl-3-butenoic acid) and M2 (3',5'-dichloro-2-hydroxy-2-methylbut-3-enanilide). Both metabolites, in a dose-dependent manner, target androgen receptor to the nucleus and inhibit androgen-induced transactivation mediated by the mouse mammary tumor virus promoter. 3',5'-Dichloro-2-hydroxy-2-methylbut-3-enanilide is a 50-fold more potent inhibitor than (2-[[3,5-dichlorophenyl)-carbamoyl]oxy]-2-methyl-3-butenoic acid) and only 2-fold less than hydroxyflutamide. In the presence of dihydrotestosterone (50 nM), 3',5'-dichloro-2-hydroxy-2-methylbut-3-enanilide (0.2-10 uM) inhibits androgen-induced androgen receptor binding to androgen response element DNA. In the absence of dihydrotestosterone, concentrations of 10 uM 3',5'-dichloro-2-hydroxy-2-methylbut-3-enanilide or hydroxyflutamide promote androgen receptor binding to androgen response element DNA and activation of transcription. Agonist activities of 3',5'-dichloro-2-hydroxy-2-methylbut-3-enanilide and hydroxyflutamide occur at 10-fold lower concentrations with the mutant androgen receptor (Thr877 to Ala) endogenous to LNCaP human prostate cancer cells. The results indicate that androgen antagonists can act as agonists, depending on ligand binding affinity, concentration, and the presence of competing natural ligands.[Wong C et al; J Biol Chem 270 (34): 19998-20003 (1995)]**PEER REVIEWED**
  
• When pregnant rats are exposed to high doses (100 and 200 mg/kg/d) of the antiandrogenic pesticide V, sex differentiation of the male offspring is disrupted in a manner that closely resembles that of the antiandrogenic drug flutamide. Treated males display alterations of the external genitalia and lower reproductive tract, including hypospadias, cleft phallus, ectopic testes and vaginal pouches ... These effects are likely due to metabolites of V that competitively inhibit the binding of androgens to their receptor ... In contrast, even the highest does of V did not block androgen-dependent differentiation of the Wolffian duct derivatives. Here, our objectives were to determine those measures of male sex differentiation most sensitive to the antiandrogenic effects of V. Tot his end, pregnant rats were dosed with lower doses of V (0, 3.12, 6.25, 12.5, 25, 50 or 100 mg/kg/d) from gestational day 14 to postnatal day 3, and reproductive function of the male offspring was monitored for 11 months. Adverse reproductive effects ranged from infertility, reduced ejaculated sperm counts and hypospadias at 50 and 100 mg/kg/d, to subtle reductions of anogenital distance at 3 and 6 mg/kg/d. At the intermediate doses, retained nipples and reduced ventral prostate and seminal vesicle weights were detected. These data demonstrate that doses of V 15-fold below those that reduced fertility shortened anogenital distance and reduced sex accessory gland weights. It is of concern that standard multigenerational reproductive toxicity tests rely primarily on fertility to detect reproductive hazard because chemicals like V, that disrupt perinatal endocrine function, alter sex differentiation at doses well below those that affect fertility. [Gray LE Jr et al; Biol Reprod 50 (Suppl 1): 101 (1994)]**PEER REVIEWED**
  
• In humans and rodents, exposure to hormonally active chemicals during sex differentiation can produce a wide range of abnormal sexual phenotypes including masculinized and defeminized females and feminized and demasculinized males. Although numerous "environmental estrogens," including pesticides, toxic substances (PCBs), and plant and fungal estrogens, have been shown to alter mammalian sex differentiation, similar information on environmental androgens is lacking. Recently, the fungicide vinclozolin (V) was found to inhibit sexual differentiation in male rats in an antiandrogenic manner. In the present study, vinclozolin was administered to pregnant rats (p.o.) at 0, 100, or 200 mg/kg/day in corn oil during the period of sex differentiation (Gestational Day 14 to Postnatal Day 3) to examine the demasculinizing effect of this fungicide more closely. In both groups of vinclozolin-treated male offspring, anogenital distance was female like at birth, and nipple development was prominent at 2 wk of age. After puberty, most of the vinclozolin-treated male offspring were unable to attain intromission even though they all mounted sexually receptive females. The vinclozolin-treated male offspring that appeared to achieve intromission, failed to ejaculate normally, as no sperm were found in the uterus after overnight matings. A factor in the abnormal ejaculation was that all vinclozolin-treated male offspring had cleft phallus with hypospadias. In addition, a number of unusual reproductive malformations were noted when the males were necropsied at 1 yr. Many vinclozolin-treated male offspring had suprainguinal ectopic scrota/testes, a vaginal pouch, epididymal granulomas, and small to absent sex accessory glands. During the study, about 25% of the vinclozolin-treated males died as a result of bladder stones, hydroureter, or hydronephrosis, while other males displayed these lesions at necropsy. While some of the above malformations in male offspring can also be produced by perinatal administration of a potent estrogen, like DES, vinclozolin-treated female offspring did not display any estrogen-like alterations of reproductive development or fecundity. The only change seen in the female offspring was a reduced anogenital distance during neonatal life. Our observation of perinatal-induced agenesis of the prostate and blocked testicular descent, a pattern of malformations nearly identical to the reported for the antiandrogen flutamide, is consistent with other recent evidence that this fungicide is an androgen-receptor antagonist. [Gray LE Jr et al; Toxicol Appl Pharmacol 129 (1): 46-52 (1994)]**PEER REVIEWED**
  
• Recent studies with vinclozolin, a dicarboximide fungicide, demonstrate that perinatal exposure to 100 mg vinclozolin /kg/day from Gestational Day 14 through Postnatal Day 3 inhibits morphological sex differentiation. At 1 yr, treated male rats exhibited hypospadias, cleft phallus, suprainguinal ectopic testes, a vaginal pouch, epididymal and testicular granulomas, and atrophic seminal vesicles and ventral prostate glands. This pattern of malformations suggests that this fungicide possesses antiandrogenic activity. To test this hypothesis, we examine the ability of vinclozolin to inhibit the conversion of testosterone to the more potent androgen 5 alpha-dihydrotestosterone via 5 alpha-reductase (EC 1.3.1.22) and to compete with androgen for binding to the androgen receptor. The results indicate that neither vinclozolin nor its degradation products, 2-[[(3,5-dichlorophenyl)-carbamoyl]oxy]-2-methyl-3-butenoic acid (M1) and 3',5'-dichloro-2-hydroxy-2-methylbut-3-enanilide (M2), inhibit 5 alpha-reductase activity. Although the ability of vinclozolin to compete with androgen for binding to the androgen receptor was weak (Ki > 700 uM), the two vinclozolin metabolites, 2-[[(3,5-dichlorophenyl)-carbamoyl]oxy]-2-methyl-3-butenoic acid and 3',5'-dichloro-2-hydroxy-2-methylbut-3-enanilide, were effective antagonists of androgen receptor binding (Ki = 92 and 9.7 uM, respectively). As the concentrations of 2-[[(3,5-dichlorophenyl)-carbamoyl]oxy]-2-methyl-3-butenoic acid in the serum of pregnant rats and their pups on Postnatal Day 3 meet or exceed the in vitro Ki for androgen receptor inhibition, we suggest that the demasculinizing effects of vinclozolin exposure in vivo also may be mediated via the antiandrogenic metabolites 2-[[(3,5-dichlorophenyl)-carbamoyl]oxy]-2-methyl-3-butenoic acid and/or 3',5'-dichloro-2-hydroxy-2-methylbut-3-enanilide.[Kelce WR et al; Toxicol Appl Pharmacol 126 (2): 276-85 (1994)]**PEER REVIEWED**
  

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Human Toxicity Values

• None found

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Non-Human Toxicity Values

• None found

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Absorption, Distribution and Excretion

• None found

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Metabolism/Metabolites

• ... Has metabolites that can act as androgen antagonists. [Klaassen, C.D., M.O. Amdur, Doull J. (eds.). Casarett and Doull's Toxicology. The Basic Science of Poisons. 5th ed. New York, NY: McGraw-Hill, 1995., p. 549]**PEER REVIEWED**
  
• metabolite is buteonic acid derivative and an enanilide metabolite [Klaassen, C.D., M.O. Amdur, Doull J. (eds.). Casarett and Doull's Toxicology. The Basic Science of Poisons. 5th ed. New York, NY: McGraw-Hill, 1995., p. 562]**PEER REVIEWED**
  

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TSCA Test Submissions

• None found

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Footnotes

¹ Source: the National Library of Medicine's Hazardous Substance Database, 10/28/2007.