Behavioral responses of rats exposed to long-term dietary vinclozolin

Effect of Pesticide Vinclozolin Toxicity Exposure on Cardiac Oxidative Stress and Myocardial Damage

(1) Background: Vinclozolin is a popular fungicide used in fruit, ornamental plants, and vegetable crops. It has recently been seen that prolonged exposure to VZN can cause human or animal health damage to various organs, but little is known to date about its cardiovascular effects. In this study, we addressed the chronic effects of VZN on the myocardium and the enzymes involved in the cardiovascular function. (2) Methods: The animals were divided into four groups: group 1 served as the control, group 2 received 1 mg/kg of VZN by gavage, group 3 received 30 mg/kg of VZN by gavage, and group 4 received 100 mg/kg of VZN by gavage, for 30 days. (3) Results: Results showed that 100 mg/kg VZN markedly increased the plasma concentration of cardiac markers (CK-MB, cTnT, ANP, BNP). Moreover, compared to the control group, VZN treatment decreased the activity of SOD, CAT, and GPx, and downregulated the mRNA expression levels of Nrf2. Furthermore, collagen deposition was amplified owing to 100 mg/kg VZN cardiotoxicity. This harmful effect was confirmed by a histological study using hematoxylin and eosin (H&E) and Masson's trichrome staining. (4) Conclusion: Overall, our results proved the cardiotoxicity caused by chronic exposure to VZN.

Effects of chronic exposure to the fungicide vinclozolin on gut microbiota community in an aquatic turtle

Environmental issues associated with the widespread use of agricultural chemicals are being seriously concerned. Of them, toxicological impacts of fungicides in aquatic organisms are often overlooked. Here, soft-shelled turtle (Pelodiscus sinensis) hatchlings were exposed to different concentrations of vinclozolin (0, 5, 50, 500 and 5000 μg/L) for 60 days to investigate the impact of fungicide exposure on their gut microbial composition and diversity. Vinclozolin exposure significantly affected the composition of the gut microbiota in hatchling turtles. Unexpectedly, gut bacterial diversity and richness of vinclozolin-exposed turtles (but not for the 5000 μg/L-exposed group) were relatively higher than control ones. At the phylum level, the abundance of Firmicutes was decreased, while that of Proteobacteria was increased in high-concentration groups. At the genus level, some bacterial genera including Cellulosilyticum, Romboutsia and Clostridium_sensu_stricto, were significantly changed after vinclozolin exposure; and some uniquely observed in high-concentration groups. Gene function predictions showed that genes related to amino acid metabolism were less abundant, while those related to energy metabolism more abundant in high-concentration groups. The prevalence of some pathogens inevitably affected gut health status of vinclozolin-exposed turtles. Such gut microbiota dysbiosis might be potentially linked with hepatic metabolite changes induced by vinclozolin exposure.

Risky business: Changes in boldness behavior in male Siamese fighting fish, Betta splendens, following exposure to an antiandrogen

Components of boldness, such as activity level and locomotion, influence an individual's ability to avoid predators and acquire resources, generating fitness consequences. The presence of endocrine disrupting chemicals (EDCs) in the aquatic environment may affect fitness by changing morphology or altering behaviors like courtship and exploration. Most research on EDC-generated behavioral effects has focused on estrogen mimics and reproductive endpoints. Far fewer studies have examined the effects of other types of EDCs or measured non-reproductive behaviors. EDCs with antiandrogenic properties are present in waterways yet we know little about their effects on exposed individuals although they may produce effects similar to those caused by estrogen mimics because they act on the same hormonal pathway. To examine the effects of antiandrogens on boldness, this study exposed male Siamese fighting fish, Betta splendens, to a high or low dose of one of two antiandrogens, vinclozolin or flutamide, and observed behavior in three boldness assays, both before and after exposure. Overall, antiandrogen exposure increased boldness behavior, especially following exposure to the higher dose. Whether or not antiandrogen exposure influenced boldness, as well as the nature and intensity of the effect, was assay-dependent. This demonstrates the importance of studying EDC effects in a range of contexts and, at least within this species, suggests that antiandrogenic compounds may generate distinct physiological effects in different situations. How and why the behavioral effects differ from those caused by exposure to an estrogen mimic, as well as the potential consequences of increased activity levels, are discussed. Exposure to an antiandrogen, regardless of dose, produced elevated activity levels and altered shoaling and exploration in male Siamese fighting fish. These modifications may have fitness consequences.

Developmental Exposure to Low Levels of Ethinylestradiol Affects Play Behavior in Juvenile Female Rats

Juvenile social play contributes to the development of adult social and emotional skills in humans and non-human animals, and is therefore a useful endpoint to study the effects of endocrine disrupters on behavior in animal models. Ethinylestradiol (EE₂) is a widely produced, powerful synthetic estrogen that is widespread in the environment mainly because is a component of the contraceptive pill. In addition, fetuses may be exposed to EE2 when pregnancy is undetected during contraceptive treatment. To understand whether exposure to EE₂ during gestation or lactation affects social play, we exposed 72 female Sprague-Dawley rats to EE₂ or vehicle either during gestation (gestation day (GD) 5 through GD 20) or during lactation (from postnatal day (PND) 1 through PND 21). Two doses of EE₂ were used to treat the dams: a lower dose in the range of possible environmental exposure (4 ng/kg/day) and a higher dose equivalent to that received during contraceptive treatment (400 ng/kg/day). Behavioral testing was carried out between PND 40 and 45. A principal component analysis of frequencies of behavioral items observed during play sessions identified three main components: defensive-like play, aggressive-like play, and exploration. Aggressive-like play was significantly increased by both doses of EE₂, and the gestational administration was in general more effective than the lactational one. Defensive-like play and exploration were not significantly affected by treatment. This research showed that low and very low doses of EE₂ that mimic clinical or environmental exposure during development can affect important aspects of social behavior even during restricted time windows.

Early endocrine disruptors exposure acts on 3T3-L1 differentiation and endocrine activity

Introduction: Data from last years suggested that early exposure to endocrine disruptors (EDs) can predispose newborns to endocrine dysfunction of adipocytes, obesity, and associated disorders. The implication of EDs at low doses on adipocyte development has been poorly investigated. For instance, vinclozolin (V) is a dicarboximide fungicide widely used in agriculture since the 90's, alone or in mixture with genistein (G), an isoflavonoid from Leguminosae. This study aims to identify the effect of vinclozolin alone or with genistein, on adipose tissue properties using cell culture.

Methods: In steroid-free conditions, 3T3-L1 pre-adipocytes were induced to differentiate in the presence of EDs, singularly or in mixtures, for 2 days. DNA and triglyceride (TG) levels were measured on days 0, 2 and 8 of differentiation. Leptin secretion was measured only on the eighth day.

Results: We show that low doses of G (25 µM) and V (0.1 µM) inhibit pre-adipocytes differentiation. This inhibition has been represented by a decreasing in DNA content (µg/well) and decreasing in TG accumulation (mg/mL) in 3T3-L1 cells. Nevertheless, V increased the anti-adipogenic properties of G.

Conclusion: This study confirms that EDs singularly or in mixtures, introduced during early stages of life, could affect the differentiation and the endocrine activity of adipocytes, and can act as potential factors for obesity.

Developmental treatment with ethinyl estradiol, but not bisphenol A, causes alterations in sexually dimorphic behaviors in male and female Sprague Dawley rats

The developing central nervous system may be particularly sensitive to bisphenol A (BPA)-induced alterations. Here, pregnant Sprague Dawley rats (n = 11-12/group) were gavaged daily with vehicle, 2.5 or 25.0 μg/kg BPA, or 5.0 or 10.0 μg/kg ethinyl estradiol (EE2) on gestational days 6-21. The BPA doses were selected to be below the no-observed-adverse-effect level (NOAEL) of 5 mg/kg/day. On postnatal days 1-21, all offspring/litter were orally treated with the same dose. A naïve control group was not gavaged. Body weight, pubertal age, estrous cyclicity, and adult serum hormone levels were measured. Adolescent play, running wheel activity, flavored solution intake, female sex behavior, and manually elicited lordosis were assessed. No significant differences existed between the vehicle and naïve control groups. Vehicle controls exhibited significant sexual dimorphism for most behaviors, indicating these evaluations were sensitive to sex differences. However, only EE2 treatment caused significant effects. Relative to female controls, EE2-treated females were heavier, exhibited delayed vaginal opening, aberrant estrous cyclicity, increased play behavior, decreased running wheel activity, and increased aggression toward the stimulus male during sexual behavior assessments. Relative to male controls, EE2-treated males were older at testes descent and preputial separation and had lower testosterone levels. These results suggest EE2-induced masculinization/defeminization of females and are consistent with increased volume of the sexually dimorphic nucleus of the preoptic area (SDN-POA) at weaning in female siblings of these subjects (He, Z., Paule, M. G. and Ferguson, S. A. (2012) Low oral doses of bisphenol A increase volume of the sexually dimorphic nucleus of the preoptic area in male, but not female, rats at postnatal day 21. Neurotoxicol. Teratol. 34, 331-337). Although EE2 treatment caused pubertal delays and decreased testosterone levels in males, their behaviors were within the range of control males. Conversely, BPA treatment did not alter any measured endpoint. Similar to our previous reports (Ferguson, S. A., Law, C. D. Jr and Abshire, J. S. (2011) Developmental treatment with bisphenol A or ethinyl estradiol causes few alterations on early preweaning measures. Toxicol. Sci. 124, 149-160; Ferguson, S. A., Law, C. D. and Abshire, J. S. (2012) Developmental treatment with bisphenol A causes few alterations on measures of postweaning activity and learning. Neurotoxicol. Teratol. 34, 598-606), the BPA doses and design used here produced few alterations.

Current concepts in neuroendocrine disruption

In the last few years, it has become clear that a wide variety of environmental contaminants have specific effects on neuroendocrine systems in fish, amphibians, birds and mammals. While it is beyond the scope of this review to provide a comprehensive examination of all of these neuroendocrine disruptors, we will focus on select representative examples. Organochlorine pesticides bioaccumulate in neuroendocrine areas of the brain that directly regulate GnRH neurons, thereby altering the expression of genes downstream of GnRH signaling. Organochlorine pesticides can also agonize or antagonize hormone receptors, adversely affecting crosstalk between neurotransmitter systems. The impacts of polychlorinated biphenyls are varied and in many cases subtle. This is particularly true for neuroedocrine and behavioral effects of exposure. These effects impact sexual differentiation of the hypothalamic-pituitary-gonadal axis, and other neuroendocrine systems regulating the thyroid, metabolic, and stress axes and their physiological responses. Weakly estrogenic and anti-androgenic pollutants such as bisphenol A, phthalates, phytochemicals, and the fungicide vinclozolin can lead to severe and widespread neuroendocrine disruptions in discrete brain regions, including the hippocampus, amygdala, and hypothalamus, resulting in behavioral changes in a wide range of species. Behavioral features that have been shown to be affected by one or more these chemicals include cognitive deficits, heightened anxiety or anxiety-like, sociosexual, locomotor, and appetitive behaviors. Neuroactive pharmaceuticals are now widely detected in aquatic environments and water supplies through the release of wastewater treatment plant effluents. The antidepressant fluoxetine is one such pharmaceutical neuroendocrine disruptor. Fluoxetine is a selective serotonin reuptake inhibitor that can affect multiple neuroendocrine pathways and behavioral circuits, including disruptive effects on reproduction and feeding in fish. There is growing evidence for the association between environmental contaminant exposures and diseases with strong neuroendocrine components, for example decreased fecundity, neurodegeneration, and cardiac disease. It is critical to consider the timing of exposures of neuroendocrine disruptors because embryonic stages of central nervous system development are exquisitely sensitive to adverse effects. There is also evidence for epigenetic and transgenerational neuroendocrine disrupting effects of some pollutants. We must now consider the impacts of neuroendocrine disruptors on reproduction, development, growth and behaviors, and the population consequences for evolutionary change in an increasingly contaminated world. This review examines the evidence to date that various so-called neuroendocrine disruptors can induce such effects often at environmentally-relevant concentrations.

Perinatal xenohormone exposure impacts sweet preference and submandibular development in male rats

OBJECTIVE

To determine the effect of perinatal exposure to low doses of genistein and/or vinclozolin on submandibular salivary gland (SSG) development in juvenile and adult male rats and to establish a link with sweet preference.

MATERIAL AND METHODS

Female rats received orally (1 mg kg(-1) body weight/day) genistein and vinclozolin, alone or in combination, from the first gestational day up to weaning. Sweet preference was assessed at weaning and in adulthood in male offspring; submandibular glands were then collected to study the morphogenesis and mRNA expression of steroid receptors, growth factors and taste related proteins.

RESULTS

Exposure to genistein and/or vinclozolin resulted in a higher saccharin intake on postnatal day 25 (P < 0.05) linked to a higher number of pro-acinar cells (P < 0.01) and mRNA expression of progesterone receptor, growth factors and gustine (P < 0.01). These increases disappeared in adulthood, but mRNA expressions of sex hormone receptors and growth factors were strongly repressed in all treated groups (P < 0.01).

CONCLUSION

Our findings confirm that the SSG are target for xenohormones and provide evidence that perinatal exposure to low doses of genistein and/or vinclozolin could simultaneously disrupt not only the salivary gland prepubertal development and sweet intake but also endocrine gene mRNA expression later in life.

Effects of Aromatase Inhibition on the Physical Activity Levels of Male Mice

Increasing activity levels in an inactive population can lead to associative increases in health and well-being. Both biologic and genetic factors have been identified that alter physical activity levels in humans and rodents with an extensive early literature regarding sex steroid effects on physical activity. Currently, it is suggested that the androgens require conversion to estrogens prior to eliciting any effects on activity patterns. Recent data contradicts this assertion; thus, the purpose of this study was to evaluate the necessity of the aromatase complex in activity regulation. Wheel running was assessed in male C57BL/6J mice under various sex steroid-disrupted and aromatase-inhibited conditions. Inhibition of the aromatase complex was achieved through administration of two different aromatase inhibiting substances-letrozole and exemestane. Wheel running was unaffected by aromatase inhibition in reproductively intact and sex steroid supplemented mice. Orchidectomy significantly reduced wheel running activity. Steroid replacement recovered wheel running to pre-surgical levels; however, aromatase inhibition did not further affect wheel running levels. The recovery of wheel running in mice with androgen supplementation and the further persistence of wheel running in mice with compromised aromatase function suggests that the androgens-testosterone in particular-may directly affect wheel running patterns in male mice.

Pesticide exposure and neurodevelopmental outcomes: review of the epidemiologic and animal studies

Assessment of whether pesticide exposure is associated with neurodevelopmental outcomes in children can best be addressed with a systematic review of both the human and animal peer-reviewed literature. This review analyzed epidemiologic studies testing the hypothesis that exposure to pesticides during pregnancy and/or early childhood is associated with neurodevelopmental outcomes in children. Studies that directly queried pesticide exposure (e.g., via questionnaire or interview) or measured pesticide or metabolite levels in biological specimens from study participants (e.g., blood, urine, etc.) or their immediate environment (e.g., personal air monitoring, home dust samples, etc.) were eligible for inclusion. Consistency, strength of association, and dose response were key elements of the framework utilized for evaluating epidemiologic studies. As a whole, the epidemiologic studies did not strongly implicate any particular pesticide as being causally related to adverse neurodevelopmental outcomes in infants and children. A few associations were unique for a health outcome and specific pesticide, and alternative hypotheses could not be ruled out. Our survey of the in vivo peer-reviewed published mammalian literature focused on effects of the specific active ingredient of pesticides on functional neurodevelopmental endpoints (i.e., behavior, neuropharmacology and neuropathology). In most cases, effects were noted at dose levels within the same order of magnitude or higher compared to the point of departure used for chronic risk assessments in the United States. Thus, although the published animal studies may have characterized potential neurodevelopmental outcomes using endpoints not required by guideline studies, the effects were generally observed at or above effect levels measured in repeated-dose toxicology studies submitted to the U.S. Environmental Protection Agency (EPA). Suggestions for improved exposure assessment in epidemiology studies and more effective and tiered approaches in animal testing are discussed.

Development of partial life-cycle experiments to assess the effects of endocrine disruptors on the freshwater gastropod Lymnaea stagnalis: a case-study with vinclozolin

Long-term effects of endocrine disruptors (EDs) on aquatic invertebrates remain difficult to assess, mainly due to the lack of appropriate sensitive toxicity test methods and relevant data analysis procedures. This study aimed at identifying windows of sensitivity to EDs along the life-cycle of the freshwater snail Lymnaea stagnalis, a candidate species for the development of forthcoming test guidelines. Juveniles, sub-adults, young adults and adults were exposed for 21 days to the fungicide vinclozolin (VZ). Survival, growth, onset of reproduction, fertility and fecundity were monitored weekly. Data were analyzed using standard statistical analysis procedures and mixed-effect models. No deleterious effect on survival and growth occurred in snails exposed to VZ at environmentally relevant concentrations. A significant impairment of the male function occurred in young adults, leading to infertility at concentrations exceeding 0.025 μg/L. Furthermore, fecundity was impaired in adults exposed to concentrations exceeding 25 μg/L. Biological responses depended on VZ concentration, exposure duration and on their interaction, leading to complex response patterns. The use of a standard statistical approach to analyze those data led to underestimation of VZ effects on reproduction, whereas effects could reliably be analyzed by mixed-effect models. L. stagnalis may be among the most sensitive invertebrate species to VZ, a 21-day reproduction test allowing the detection of deleterious effects at environmentally relevant concentrations of the fungicide. These results thus reinforce the relevance of L. stagnalis as a good candidate species for the development of guidelines devoted to the risk assessment of EDs.

Effects of vinclozolin, an anti-androgen, on affiliative behavior in the Dark-eyed Junco, Junco hyemalis

Endocrine disrupting chemicals (EDCs) produce changes in physiology and behavior via diverse mechanisms including acting as hormone mimics or antagonists, affecting intracellular signaling pathways, and altering hormone production pathways. The fungicide vinclozolin acts as an anti-androgen and is known to affect affiliative behaviors in rodents, fish and amphibians. To investigate the possible effects of exposure to EDCs on reproductive behavior in a wild population of songbirds, we examined the effects of vinclozolin in wild-caught Dark-eyed Juncos (Junco hyemalis). For this and many other temperate songbird species, testosterone has powerful activational effects on affiliative behaviors in adulthood. We hypothesized that vinclozolin would affect male behaviors associated with female preference. Male juncos received daily oral gavage for 10 weeks with 2mM vinclozolin in vehicle or vehicle alone. Juncos were photostimulated (16L:8D) to induce breeding behavior. Each pair of a treated and non-treated male was presented to an estrogen-primed female to assess female preference. Seven of eight females exhibited a strong preference for a male exposed to vinclozolin over a control male (p=0.01). The only significant difference in measured male behaviors was increased beak wiping in controls (p=0.006) and there was no difference in gonad size or brain weight (p>0.05 for each). Our data suggest that estrogen-primed female juncos prefer to associate with male juncos exposed to this anti-androgen. This finding demonstrates that environmentally occurring anti-androgens can affect the social behavior of this species. To our knowledge, this is the first study to show that vinclozolin has effects on the social behavior of songbirds.

Learning deficits expressed as delayed extinction of a conditioned running response following perinatal exposure to vinclozolin

Vinclozolin (Vz) is one member of a group of fungicides whose metabolites are androgen receptor antagonists. These fungicides have been shown to block androgen-driven development and compromise reproductive function. The current study sought to determine if Vz also affects learning following exposure to low doses during the perinatal period. To test this, an androgen-dependent behavior was examined, the extinction of a previously reinforced running response. Pregnant Long-Evans rats were administered a daily oral dose of 0, 1.5, 3, 6 or 12 mg/kg Vz from the 14th day of gestation through postnatal day 3. After reaching adulthood, male and female offspring were trained to run through a short alleyway for food reinforcement. Acquisition of the response was not affected by Vz exposure. However, males required more trials than females for response extinction once food was no longer available in the apparatus. Males exposed to 6 or 12 mg/kg Vz failed to show any extinction by the end of the procedure, while the lowest dose of Vz appeared to facilitate extinction in both male and female offspring. These results demonstrate that endocrine disrupting antiandrogens can alter nervous system development in addition to the reproductive system.

Myelotoxicity in genistein-, nonylphenol-, methoxychlor-, vinclozolin- or ethinyl estradiol-exposed F1 generations of Sprague–Dawley rats following developmental and adult exposures

The myelotoxicity of five endocrine active chemicals was evaluated in F1 generation of Sprague-Dawley rats following developmental and adult exposures at three concentration levels. Rats were exposed to genistein (GEN: 25, 250 and 1250 ppm), nonylphenol (NPH: 25, 500 and 2000 ppm), methoxychlor (MXC: 10, 100 and 1000 ppm), vinclozolin (VCZ: 10, 150 and 750 ppm) and ethinyl estradiol (EE2: 5, 25 and 200 ppb) gestationally and lactationally through dams from day 7 of gestation and through feed after weaning on postnatal day (PND) 22 to PND 64. The parameters examined included the number of recovered bone marrow cells, DNA synthesis, and colony forming units (CFU) in the presence of granulocyte macrophage-colony stimulating factor (GM-CSF), macrophage colony-stimulating factor (M-CSF) and erythropoietin. Except for the EE2, the concentrations of other individual chemicals in the diet were in an approximate range that allowed for a comparison to be made in terms of myelotoxic potency. Decreases in the DNA synthesis, CFU-GM and CFU-M seemed to be the common findings among the alterations induced by these compounds. Using the numbers of alterations induced by each chemical in the parameters examined as criteria for comparison, the order of myelotoxic potency in F(1) males was: GEN>MXC>NPH>VCZ; the order in females: GEN>NPH>VCZ. Additionally, some of the functional changes induced by these compounds were gender-specific or dimorphic. Overall, the results demonstrated that developmental and adult exposures of F1 rats to these endocrine active chemicals at the concentrations tested had varied degrees of myelotoxicity with GEN being the most potent. Furthermore, the sex-specific effects of these chemicals in F1 male and female rats suggest that there may be interactions between these compounds and sex hormone in modulating these responses.

Chronic Oral Treatment with 13-cis-Retinoic Acid (Isotretinoin) or all-trans-Retinoic Acid Does Not Alter Depression-Like Behaviors in Rats

Oral treatment with the anti-acne drug Accutane (isotretinoin, 13-cis-retinoic acid) has been associated with suicide ideation and depression. Here, depression-like behaviors (i.e., behavioral despair and anhedonia) were quantified in adult Sprague-Dawley rats gavaged daily beginning at postnatal day (PND) 82 with 13-cis-RA (7.5 or 22.5 mg/kg) or all-trans-retinoic acid (10 or 15 mg/kg ). Tested at PND 130-131 in the Forced Swim Test, 7.5 mg/kg 13-cis-RA marginally decreased immobility and slightly increased climb/struggle durations whereas neither all-trans-retinoic acid group differed from controls. Voluntary saccharin solution (0.03%) intake at PND 102-104 and PND 151-153 was not different from controls in any treated group, although all RA-treated groups had lower intakes. Swim speed in a water maze at PND 180 was similar across groups, indicating no RA-induced differences in physical ability. Open field activity was mildly decreased at PND 91 in 7.5 mg/kg-treated males only, but it was within the control range at PND 119, 147, and 175. Thus, at serum levels similar to those in humans receiving the drug, chronic 13-cis-RA treatment did not severely affect depression-like behaviors in rats. These data do not substantiate the hypothesis of 13-cis-RA-induced depression.

Perinatal exposure to low levels of the environmental antiandrogen vinclozolin alters sex-differentiated social play and sexual behaviors in the rat

In this study we examined the effects of exposure to the antiandrogenic fungicide vinclozolin (Vz) on the development of two sex-differentiated behaviors that are organized by the perinatal actions of androgens. Pregnant Long-Evans rats were administered a daily oral dose of 0, 1.5, 3, 6, or 12 mg/kg Vz from the 14th day of gestation through postnatal day (PND)3. The social play behavior of juvenile offspring was examined on PND22 and again on PND34 during play sessions with a same-sex littermate. After they reached adulthood, the male offspring were examined with the ex copula penile reflex procedure to assess erectile function. Vz did not produce any gross maternal or neonatal toxicity, nor did it reduce the anogenital distance in male pups. We observed no effects of Vz on play behavior on PND22. However, the 12-mg/kg Vz dose significantly increased play behavior in the male offspring on PND34 compared with controls. The most dramatic increases were seen with the nape contact and pounce behavior components of play. The Vz effect was more pronounced in male than in female offspring. As adults, male offspring showed a significant reduction of erections at all dose levels during the ex copula penile reflex tests. The 12-mg/kg dose was also associated with an increase in seminal emissions. These effects demonstrate that perinatal Vz disrupts the development of androgen-mediated behavioral functions at exposure levels that do not produce obvious structural changes or weight reductions in androgen-sensitive reproductive organs.

Long term dietary methoxychlor exposure in rats increases sodium solution consumption but has few effects on other sexually dimorphic behaviors

Methoxychlor is an insecticide with estrogen-like activity, thus exposure during development might cause sexually dimorphic behavioral alterations. To evaluate this, pregnant rats consumed diets containing 0, 10, 100 or 1000 ppm methoxychlor from gestational day 7, and offspring continued on these diets until postnatal day (PND) 77. Assessments of sexually dimorphic behaviors in offspring indicated that intake of a 3.0% sodium chloride solution was significantly increased (41%) in males and females of the 1000 ppm group. No treatment group differed from controls in open field nor running wheel activity, play behavior, nor 0.3% saccharin solution intake. Offspring of the 1000 ppm group showed significantly decreased body weight, reaching 17% less than controls at PND 77, but not clearly related to their salt solution intake. During pregnancy, 1000 ppm dams consumed 23% less food and weighed 10% less than controls, but this did not affect litter outcomes. These results indicate that in rodents, developmental and chronic exposure to dietary methoxychlor alters the sexually dimorphic behavior of salt-solution intake in young adults of both sexes. Similar behavioral alterations with other xenoestrogens, and the potential for interactions among xenoestrogens, suggest that this report may minimize the true effects of dietary methoxychlor exposure.

An environmental antiandrogen, vinclozolin, alters the organization of play behavior

During mammalian sexual differentiation, the androgens, testosterone and dihydrotestosterone are critical for the organization of the male phenotype. In rats, play behavior is sexually dimorphic. Administration of exogenous androgens during the perinatal period results in masculine-like play behavior of juveniles. Recently, there has been increasing concern about the potential for environmental endocrine-disrupting chemicals (EDCs) to alter sexual differentiation in mammals. One such EDC is the fungicide and androgen receptor (AR) antagonist, vinclozolin. We tested whether developmental exposure to an EDC could alter androgen-dependent behaviors such as play. To examine this possibility, neonatal male rats were injected from Postnatal Days (PND) 2 to 3 with corn oil, pharmacological antiandrogen flutamide (50 mg/kg/day) or vinclozolin (200 mg/kg/day); whereas neonatal females were treated either with corn oil or testosterone propionate (TP, 250 microg/kg/day). At PNDs 36-37, animals were observed for social play. Behaviors associated with general social activity, such as sniffing and dorsal contact, were unaffected by treatment or sex. However, play behavior in males treated with flutamide or vinclozolin was significantly reduced to near-female levels when compared to control males. Play behavior in females exposed to TP during the neonatal period was significantly increased when compared with control females. Hence, this study suggests that perinatal exposure to vinclozolin, an environmental antiandrogen, can alter androgen-dependent behavior, such as play, in the male rat.

Dietary ethinyl estradiol exposure during development causes increased voluntary sodium intake and mild maternal and offspring toxicity in rats

Exogenous estrogen exposure during development often results in behavioral masculinization and/or defeminization of genetic females. Genetic males may be defeminized, hypermasculinized or even demasculinized after similar treatment. Here, pregnant Sprague-Dawley rats consumed phytoestrogen-free diets containing 0, 1, 5 or 200 ppb EE(2) beginning on gestational day (GD) 7. Offspring were weaned to the same maternal diet and maintained gonadally intact. There were mild effects on body weight and food consumption in dams of the 200 ppb group and their offspring weighed less at birth than those of the control group; however, gross assessments of nursing behavior were normal in all dietary groups. Postweaning, offspring of the 200 ppb group weighed less and consumed less food than controls. There were no EE(2)-related effects on open-field activity (tested at postnatal days (PND) 22-24, 43-45 and 64-66), play behavior (tested at PND 35), running wheel activity (PND 63-77) or intake of a 0.3% saccharin-flavored solution (PND 69-71). Intake of a 3.0% sodium chloride-flavored solution on PND 73-75 was increased in both male and female offspring of the 200 ppb group relative to same-sex controls, an effect that is reportedly estrogen mediated. Sodium chloride-flavored solution intake is a sexually dimorphic behavior for which female rats consume more than males. Here, while EE(2) exposure had few effects on the conventional tests of sexually dimorphic behaviors, exposure to 200 ppb in the diet appeared to feminize genetic males and hyperfeminize genetic females with regard to sodium intake.