In vivo effects of bisphenol A on the polecat (mustela putorius)

Bisphenol A (BPA), an environmental estrogen derived from the plastic industry, was given orally via incorporation into the food of 30 male and female polecats at 3 different doses (10, 50, or 250 mg/kg body weight/day) for 2 wk with 10 animals acting as controls. Several hormone levels in the plasma were determined as well as the activities of the phase I and II biotransformation enzymes 7-ethoxyresorufin O-deethylase (EROD), cytosolic glutathione S-transferase (GST), and UDP-glucuronosyltransferase (UDPGT). BPA did not cause any macroscopic effects on body mass or the health of the animals. UDPGT and GST activities increased significantly in direct correlation with increasing BPA exposure in females and UDPGT increased in a dose-related manner in males. There was no change in the plasma T4 and testosterone concentrations of the males with increasing BPA exposure. Discriminant analysis indicated that the group receiving 10 mg BPA/kg body weight/d was not different from the control group but the groups receiving 50 and 250 mg/kg body weight/d were different from the control group. This suggests physiological changes in the groups receiving 50 or 250 mg BPA/kg body weight/d.     

Effects of dark-rearing on triphenyl phosphate-induced neuropathy in the visual system of the developing European ferret (Mustela putorius furo)

Results of a previous study in our lab (Tanaka et al., 1994) suggested that the onset of susceptibility to the organophosphorus compound triphenyl phosphite (TPP) in the developing ferret visual system might be closely related to eye opening and the onset of light stimulation. In order to explore this idea further, TPP was administered to ferret kits that had been raised for varying periods of time in total darkness to assess whether a delay in the onset of light stimulation to the visual system might also result in a delay in its susceptibility to TPP. Ferret kits were raised from birth either in total darkness or in open-sided sheds exposed to ambient light, injected subcutaneously with TPP (888 mg/kg body weight) at 5.5, 7.5, 9.5, or 21.5 wk of age, euthanized, and perfused transcardially with a 10% formalin-saline solution 4 d after injection. Brains were sectioned parasagittally at a thickness of 40 microm and subsequently processed with the Fink-Heimer silver impregnation technique to reveal the presence of degenerating axons and terminals, and with cresyl violet stain to delineate nuclear boundaries and cell soma morphology. Comparisons among degeneration patterns present in light-reared and dark-reared kits at the four ages examined revealed that the time of onset, extent, and density of TPP-induced axonal and terminal degeneration seen in the lateral geniculate nucleus and primary visual cortex did not differ significantly between light- and dark-reared groups, with the possible exception of dark-reared kits exposed to TPP at 7.5 wk of age. In addition, neurons in the primary visual cortex showed shrinkage and increased packing densities in kits exposed to TPP in both light and dark environments, as well as in dark-reared non-injected kits. The results of this study indicate that dark-rearing does not delay the onset or lessen the severity of TPP-induced axonal and terminal degeneration in the developing visual system of the ferret. Data suggest that light activation and stimulation of the retino-geniculo-striatal visual pathway is not a necessary prerequisite for the onset of visual system susceptibility to the axonopathic effects of triphenyl phosphite.     

Age-Related Effects of Triphenyl Phosphite-Induced Delayed Neuropathy on Central Visual Pathways in the European Ferret (Mustela putorius furo)

The objective of this study was to investigate the relationshipbetween the maturation of visual system neurons and the onsetof their susceptibility to triphenyl phosphite (TPP)-induceddelayed neurotoxicity in the European ferret. We administeredsingle subcutaneous doses of TPP (1184 mg/kg body wt) to 1-to 10-week-old ferret kits to assess the effects on connectionsand neurons of the developing lateral geniculate thalamic nucleus(LGN) and primary visual cortex. Brains were processed witha modified Fink-Heimer silver-impregnation method. Axonal andterminal degeneration were first noted in the LGN of kits injectedat 5 weeks of age. The severity of the degeneration increasedin kits injected at later ages and reached adult densities andconfigurations in ferrets injected at 10 weeks of age. Degeneratingneuronal cell bodies were also present in the LGN of kits injectedat 7 weeks of age and older. In the visual cortex, axonal andterminal degeneration were consistently present in kits injectedat 8 weeks of age and attained adult-like densities in kitsinjected at 10 weeks of age. Previous studies have reportedthat the ferret visual system appears to reach anatomical maturity(as defined by mature LGN lamination patterns, the locationand density of axon terminals originating from neurons in theretina and LGN, and the migration and synaptic connections ofcortical neurons) by 4–5 weeks of age. A temporal comparisonof these normal developmental data with the degeneration dataobtained in the present study suggests that immature neuronsin the visual system of the ferret are not susceptible to TPP-in-duceddelayed neurotoxicity but only become so after they have achievedsome degree of maturity. Whether the LGN neurons undergoingdegeneration are directly affected by TPP or are showing a transneuronalresponse to loss of afferent input remains Unresolved.     

Developmental exposure to endocrine disruptors and the obesity epidemic

Xenobiotic and dietary compounds with hormone-like activity can disrupt endocrine signaling pathways that play important roles during perinatal differentiation and result in alterations that are not apparent until later in life. Evidence implicates developmental exposure to environmental hormone-mimics with a growing list of health problems. Obesity is currently receiving needed attention since it has potential to overwhelm health systems worldwide with associated illnesses such as diabetes and cardiovascular disease. Here, we review the literature that proposes an association of exposure to environmental endocrine disrupting chemicals with the development of obesity. We describe an animal model of developmental exposure to diethylstilbestrol (DES), a potent perinatal endocrine disruptor with estrogenic activity, to study mechanisms involved in programming an organism for obesity. This experimental animal model provides an example of the growing scientific field termed "the developmental origins of adult disease" and suggests new targets of abnormal programming by endocrine disrupting chemicals.     

Life style-related diseases of the digestive system: endocrine disruptors stimulate lipid accumulation in target cells related to metabolic syndrome

Many reports indicated that endocrine disruptors (EDs) affect several hormonal functions in various living things. Here, we show the effect of EDs on lipid accumulation in target cells involved in the onset of metabolic syndrome. Treatment with nonylphenol and bisphenol A, typical EDs, stimulated the accumulation of triacylglycerol in differentiated adipocytes from 3T3-L1, preadipocytes, in time- and concentration-dependent manners. Up-regulation of gene expressions involved in lipid metabolism and metabolic syndrome were observed in adipocytes treated with EDs. Similarly, stimulatory effects of EDs were also observed on the human hepatoma cell line HuH-7. These observations indicate that exposure to EDs stimulates the lipid accumulation in target cells involved in the metabolic syndrome and may cause the dysfunction of those cells, resulting in induction of metabolic syndrome.     

The endothelial cell as a metabolic and endocrine organ

Over the last fifteen years, it has become aparent that endothelial cells have a metabolic function, inactivating some vasoactive substances and activating or synthesizing others. Among the many vasoactive substances released by endothelial cells are prostacyclin and endothelium-derived relaxing factor ERDF). Both of these relax vascular smooth muscle and inhibit platelet aggregation. In addition it has been proposed that 13-hydroxyoctadecadienoic acid (13-HODE) found in resting endothelial cells prevents platelets adhering to the endothelial membrane. Sir John Vane and his colleagues suggest that these three local hormones act together to maintain the endothelial surface in a non-thrombogenic state.     

Review of the etiology of breast cancer with special attention to organochlorines as potential endocrine disruptors

Breast cancer is the most frequently diagnosed cancer among Canadian women, accounting for about 30% of all new cancer cases each year. Although the incidence of breast cancer has increased over the past 50 years, the cause of this rise is unknown. Risk factors for breast cancer may be classified into four broad categories: (1) genetic/familial, (2) reproductive/hormonal, (3) lifestyle, and (4) environmental. Established risk factors for breast cancer include older age, later age at first full-term pregnancy, no full-term pregnancies, postmenopausal obesity, and genetic factors. However, these known risk factors cannot account for the majority of cases. In the early 1990s, it was suggested that exposure to some environmental chemicals such as organochlorine compounds may play a causal role in the etiology of breast cancer through estrogen-related pathways. The relationship between organochlorines and breast cancer risk has been studied extensively in the past decade and more, and at this point there is no clear evidence to support a causal role of most organochlorine pesticides in the etiology of human breast cancer, but more evidence is needed to assess risk associated with polychlorinated biphenyls (PCBs). Future studies need to consider the combined effects of exposures, concentrate on vulnerable groups such as those with higher levels of exposure, only consider exposures occurring during the most etiologically relevant time periods, and more thoroughly consider gene-environment interactions.     

Neurotoxicity of endocrine disruptors: possible involvement in brain development and neurodegeneration

Environmental chemicals that act as endocrine disruptors do not appear to pose a risk to human reproduction; however, their effects on the central nervous systems are less well understood. Animal studies suggested that maternal exposure to endocrine-disrupting chemicals (EDC) produced changes in rearing behavior, locomotion, anxiety, and learning/memory in offspring, as well as neuronal abnormalities. Some investigations suggested that EDC exert effects on central monoaminergic neurons, especially dopaminergic neurons. Our data demonstrated that EDC attenuate the development of dopaminergic neurons, which might be involved in developmental disorders. Perinatal exposure to EDC might affect neuronal plasticity in the hippocampus, thereby potentially modulating neuronal development, leading to impaired cognitive and memory functions. Endocrine disruptors also attenuate gender differences in brain development. For example, the locus ceruleus is larger in female rats than in males, but treatments with bisphenol-A (BPA) enlarge this region in males. Some reports indicated that EDC induce hypothyroidism, which might be evidenced as abnormal brain development. Endocrine disruptors might also affect mature neurons, resulting in neurodegenerative disorders such as Parkinson's disease. The current review focused on alterations in the brain induced by EDC, specifically on the possible involvement of EDC in brain development and neurodegeneration.     

Methylmercury impairs components of the cholinergic system in captive mink (Mustela vison).

The effects of methylmercury (MeHg) on components of the cholinergic system were evaluated in captive mink (Mustela vison). Cholinergic parameters were measured in brain regions (occipital cortex, cerebellum, brain stem, basal ganglia) and blood (whole blood, plasma, serum) following an 89-day exposure to MeHg at dietary concentrations of 0, 0.1, 0.5, 1, and 2 ppm (n = 12 animals per treatment). There were no effects of MeHg on brain choline acetyltransferase, acetylcholine, and choline transporter. However, significantly higher densities of muscarinic cholinergic receptors, as assessed by 3H-quinuclidinyl benzilate binding, were measured in the occipital cortex (30.2 and 39.0% higher in the 1 and 2 ppm groups, respectively), basal ganglia (67.5 and 69.1% higher in the 0.5 and 1 ppm groups, respectively), and brain stem (64.4% higher in the 0.5 ppm group), compared to nonexposed controls. The calculated positive relationship between MeHg exposure and muscarinic cholinergic receptor levels in this dosing study were consistent with observations in wild mink. There were no MeHg-related effects on blood cholinesterase (ChE) activity, but ChE activity was significantly higher in the occipital cortex (17.0% in the 1 ppm group) and basal ganglia (34.1% in the 0.5 ppm group), compared to nonexposed controls. The parallel increases in muscarinic cholinergic receptor levels and ChE activity following MeHg exposure highlight the autoregulatory nature of cholinergic neurotransmission. In conclusion, these laboratory data support findings from wild mink and demonstrate that ecologically relevant exposures to MeHg (i.e., 0.5 ppm in diet) have the potential to alter the cholinergic system in specific brain regions.     

The adipocyte as an endocrine organ in the regulation of metabolic homeostasis

Over the past decade and a half it has become increasingly clear that adipose tissue is a much more complex organ than was initially considered and that its metabolic functions extend well beyond the classical actions of thermoregulation and of storage and release of fatty acids. In fact, it is now well established that adipose tissue plays a critical role in maintenance of energy homeostasis through secretion of a large number of adipokines that interact with central as well as peripheral organs such as the brain, liver, pancreas, and skeletal muscle to control diverse processes, such as food intake, energy expenditure, carbohydrate and lipid metabolism, blood pressure, blood coagulation, and inflammation. While many of these adipokines are adipocyte-derived and have a variety of endocrine functions, others are produced by resident macrophages and interact in a paracrine fashion to control adipocyte metabolism. It is also abundantly clear that the dysregulation of adipokine secretion and action that occurs in obesity plays a fundamental role in the development of a variety of cardiometabolic disorders, including the metabolic syndrome, type 2 diabetes, inflammatory disorders, and vascular disorders, that ultimately lead to coronary heart disease. Described herein are the traditional as well as endocrine roles of adipose tissue in controlling energy metabolism and their dysregulation in obesity that leads to development of cardiometabolic disorders, with a focus on what is currently known regarding the characteristics and roles in both health and disease of the adipocyte-derived adipokines, adiponectin, leptin, resistin, and retinol binding protein 4, and the resident macrophage-derived adipokines, tumor necrosis factor-α and interleukin-6. This article is part of a Special Issue entitled 'Central Control of Food Intake'.     

Distribution of aflatoxin B1 in tissues of mink (Mustela vison).

Seven female mink (Mustela vison) were injected intraperitoneally with a single dose of 100 mug aflatoxin B1 (14 C-label and unabeled). They were sacrificed 1, 2, 4, and 24 h after dosing. Liver, instestines, stomach, lung, kidney, brain, pancrease, spleen, urinary bladder, uterus, and bile were removed and examined for the retained radioactivity. 1 h after dosing, intestines and their contents retained the largest amount of 14C-radioacivity (18.9% of the amount that was administered) which was followed by liver (13.2%) and the bile (10.8%). At this time all other tissues retained less than 1% of the administered radioactivity. Generally, the amount of radioactivity retained in all tissues declined with time. Only 1.2 and 0.6% of the administered radioactivity was found in testines and bile, respectively, 24 h after dosing; however, the liver still contained 6.6% of the initial radioactivity. Examination of subcellular fractions of liver revealed that at all time intervals most of the radioactivity was associated with the micrososmal supernatant fluid.     

The association between some endocrine disruptors in human plasma and the occurrence of congenital hypothyroidism

Congenital hypothyroidism is a common pediatric endocrine disease. Endocrine disruptors are indicated as a possible cause of congenital hypothyroidism. We investigated the associations between endocrine disruptors and the occurrence of congenital hypothyroidism and passage of target compounds from the mother. The levels of phthalates (DEHP, MEHP, DBP, MBP and PA), alkylphenols (n-NP and t-OP), bisphenol, and isoflavones (equol, daidzein and genistein) were determined by gas chromatography–mass spectrometry (GC–MS) in infants. t-OP and PA concentrations in the patient group were significantly higher than in normal infants. Genistein concentrations in normal infants were significantly higher than in patients. We compared the plasma levels of target compounds in infants with their mothers. There was no correlation with the passage of endocrine disruptors and isoflavones from the mothers, except for t-OP, which was weakly correlated between mother and infant.     

Biotransformation of genistein and bisphenol A in cell lines used for screening endocrine disruptors

In vitro assays provide the opportunity for generating alerts for chemicals which interact with hormone receptors and are also valuable tools for mechanistic research. However, the limited capabilities of in vitro models to metabolically activate or inactivate xenobiotics may lead to misinterpretation of the in vitro data if such information is not taken into account. The aim of this study was to investigate the metabolic capabilities of human HepG2, human MCF7 and mouse HC11 cell lines used for testing endocrine disruptors (EDs) toward radiolabelled bisphenol A and genistein, two estrogenic compounds for which metabolic pathways in vivo as in vitro are well known. Incubations were performed during 12-48h with 250.10(3) cells in 12 wells plates and 5-25muM of substrates. The kinetics of formation of the metabolites were studied. Rat liver slices were used as reference for comparison with the metabolic capabilities of the cell lines. HC11 cells did not show any biotransformation capability while the major biotransformation pathways in HepG2 and MCF7 cells were conjugation to sulfate and to a lesser extent to glucuronic acid. We detected no phase I metabolite, even in rat liver slices. These results suggest that HC11 cells should be a valuable cellular system to study the intrinsic estrogenic activity of the tested compound, while HepG2 and MCF7 cells can help to take into account part of the metabolic fate of the tested compound that occur in vivo. However, since phase I enzymes are poorly or not at all expressed in these systems, their use in endocrine disruptor testing may result in false negative for compounds for which bioactivation is a prerequisite.     

The evaluation of possible role of endocrine disruptors in central and peripheral precocious puberty

Exposure to environmental chemicals can affect genetic and epigenetic molecular pathways and may cause altered growth and development. Among those exposures, endocrine-disrupting chemicals (EDCs) are of particular concern as humans are abundantly exposed to these chemicals by various means in every period of life. Several well-known environmental chemicals, including phthalates and bisphenol A (BPA), are classified as EDCs. These EDCs are suggested to play roles in early onset of puberty in girls. The aim of this study is to determine plasma phthalate (di(2-ethylhexyl)phthalate [DEHP] and its main metabolite mono(2-ethylhexyl)phthalate [MEHP]) and urinary BPA levels in girls with idiopathic central precocious puberty (CPP) and peripheral precocious puberty (PPP). This study was performed on newly diagnosed idiopathic central precocious puberty (CPP) patients (n?=?42) and peripheral precocious puberty (PPP) (n?=?42) patients, who were admitted to Keçiören Training and Research Hospital, Clinic of Pediatric Endocrinology between August 2012 and –July 2013. Nonobese healthy girls (n?=?50) were used as the control group. Urinary BPA levels were not statistically different in control, PPP and CPP groups (medians 10.91, 10.63 and 10.15?μg/g creatinine, respectively; p?>?0.05). Plasma DEHP levels were significantly higher in PPP group when compared to control. Plasma MEHP levels were not significantly different in control and PPP groups (p?>?0.05). However, in CPP group, both plasma DEHP and MEHP levels were significantly higher than control and PPP groups. This study showed that phthalates might play a role in the occurence of CPP in girls.     

Early developmental actions of endocrine disruptors on the hypothalamus, hippocampus, and cerebral cortex

Sex steroids and thyroid hormones play a key role in the development of the central nervous system. The critical role of these hormonal systems may explain the sensitivity of the hypothalamus, the cerebral cortex, and the hippocampus to endocrine-disrupting chemicals (EDC). This review examines the evidence for endocrine disruption of glial-neuronal functions in the hypothalamus, hippocampus, and cerebral cortex. Focus was placed on two well-studied EDC, the insecticide dichlorodiphenyltrichloroethane (DDT) and polychlorinated biphenyls (PCB). DDT is involved in neuroendocrine disruption of the reproductive axis, whereas polychlorinated biphenyls (PCB) interact with both the thyroid hormone- and sex steroid-dependent systems and disturb the neuroendocrine control of reproduction and development of hippocampus and cortex. These results highlight the impact of EDC on the developing nervous system and the need for more research in this area.     

Discontinued drugs in 2005: endocrine and metabolic

This perspective describes the compounds from the endocrine and metabolic area that were discontinued during the calendar year 2005. This is a continuation of a series of perspectives of each of the editorial areas summarized by Expert Opinion on Investigational Drugs. The candidates for this summary were being developed in the areas of treatment of diabetes and diabetes complications, as well as reproductive and urogenital health issues.     

Discontinued drugs in 2008: endocrine and metabolic

This perspective summarizes key compounds from the endocrine and metabolic area that were discontinued during the calendar year 2008. This is a continuation in a series of perspectives of each of the editorial areas summarized by Expert Opinion on Investigational Drugs. The candidates covered in this summary were being developed for the treatment of diabetes, diabetic complications, anti-atherosclerosis and obesity.     

Discontinued drugs in 2005: endocrine and metabolic

This perspective describes the compounds from the endocrine and metabolic area that were discontinued during the calendar year 2005. This is a continuation of a series of perspectives of each of the editorial areas summarized by Expert Opinion on Investigational Drugs. The candidates for this summary were being developed in the areas of treatment of diabetes and diabetes complications, as well as reproductive and urogenital heath issues.     

Effects of some endocrine disruptors on the proliferation and viability of human endometrial endothelial cells in vitro

Endocrine disrupting chemicals (EDCs) pose a potential threat to human reproductive health. We studied the proliferation and viability of human endometrial endothelial cells (HEECs) in vitro after exposure to 2,2-bis(o,p-chlorophenyl)-1,1,1-trichloroethane (o,p′-DDT), 3,3′,4,4′-tetrachlorobiphenyl (CB 77), 3,3′,4,4′,5-pentachlorobiphenyl (CB 126), di-n-butyl phthalate (DBP), bisphenol A (BPA), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and 17β-oestradiol, progesterone, 17-ethynyl oestradiol and levonorgestrel. Cell proliferation was studied using immunocytochemistry for PCNA expression and a 5-bromo-2′-deoxyuridine assay. Cell viability was studied by vital staining with propidium iodide and Hoechst 33258. HEECs in primary culture responded with increased proliferation to oestradiol and with decreased proliferation to levonorgestrel and the EDCs. Some EDCs also affected cell viability and increased the proportion of necrotic cells. However, the decrease in proliferation in response to DBP and TCDD cannot be explained by cell death. In light of these results, it is possible that the EDCs could have effects in vivo as well as in vitro, and influence processes involving for example endometrial angiogenesis.