Effects of ethinylestradiol and of an environmentally relevant mixture of xenoestrogens on steroidogenic gene expression and specific transcription factors in zebrafish

Environmentally relevant estrogens impaired spermatogenesis and sexual behaviors in male and female zebrafish

Environmental estrogens (EEs) are found extensively in natural waters and negatively affect fish reproduction. Research on the reproductive toxicity of EEs mixtures in fish at environmentally relevant concentrations is scarce. In this study, adult male zebrafish were exposed for 60 days to EES (a mixture of EEs), EE2-low (5.55 ng/L, with an estrogenic potency equal to EES), and EE2-high (11.1 ng/L). After exposure, the expression levels of vtg1, vtg3, and esr1 in the livers in EES-treated fish remained unaltered, whereas they were significantly increased in EE2-treated fish. Both EE2-high and EES exposures notably reduced the gonad somatic index and sperm count. A disrupted spermatogenesis was also observed in the testes of EE2-high- and EES-exposed fish, along with an alteration in the expression of genes associated with spermatogonial proliferation (pcna, nanog), cell cycle transition (cyclinb1, cyclind1), and meiosis (aldh1a2, cyp26a1, sycp3). Both EE2 and EES significantly lowered plasma 11-ketotestosterone levels in males, likely by inhibiting the expression level of genes for its synthesis (scc, cyp17a1 and cyp11b2), and increased 17β-estradiol (E2) levels, possibly through upregulating the expression of cyp19a1a. A significant increase in tnfrsf1a expression and the tnfrsf1a/tnfrsf1b ratio in EE2-high and EES-treated males also suggests increased apoptosis via the extrinsic pathway. Further investigation showed that both EE2-high and EES diminished the sexual behavior of male fish, accompanied with reduced E2 levels in the brain and the expression of genes in the kisspeptin/gonadotropin-releasing hormone system. Interestingly, the sexual behavior of unexposed females paired with treated males was also reduced, indicating a synergistic effect. This study suggests that EES have a more severe impact on reproduction than EE2-low, and EEs could interfere not only with spermatogenesis in fish, but also with the sexual behaviors of both exposed males and their female partners, thereby leading to a more significant disruption in fish reproduction.

Estetrol/drospirenone versus 17α-ethinylestradiol/drospirenone: An extended one generation test to evaluate the endocrine disruption potential on zebrafish (Danio rerio)

Combined oral contraceptives, comprising of both an oestrogen and a progestin component, are released in aquatic environments and potentially pose a risk to aquatic wildlife by their capacity to disrupt physiological mechanisms. In this study, the endocrine disruptive potential of two mixtures, 17α-ethinylestradiol (EE2), a synthetic oestrogen, or estetrol (E4), a natural oestrogen, with the progestin drospirenone (DRSP) have been characterised in three generations of zebrafish, according to an adapted Medaka Extended One Generation Reproduction Test. Zebrafish (Danio rerio) were exposed to a range of concentrations of EE2/DRSP and E4/DRSP (∼1×, ∼3×, ∼10× and ∼30× predicted environmental concentration, PEC). Survival, growth, hatching success, fecundity, fertilisation success, vitellogenin (VTG), gonad histopathology, sex differentiation, and transcriptional analysis of genes related to gonadal sex steroid hormones synthesis were assessed. In the F0 generation, exposure to EE2/DRSP at ∼10 and ∼30× PEC decreased fecundity and increased male VTG concentrations. The highest concentration of EE2/DRSP also affected VTG concentrations in female zebrafish and the expression of genes implicated in steroid hormones synthesis. In the F1 generation, sex determination was impaired in fish exposed to EE2/DRSP at concentrations as low as ∼3× PEC. Decreased fecundity and fertility, and abnormal gonadal histopathology were also observed. No effects were observed in the F2 generation. In contrast, E4/DRSP induced only minor histopathological changes and an increase in the proportion of males, at the highest concentration tested (∼30× PEC) in the F1 generation and had no effect on hatching success of F2 generation. Overall, this study suggests that the combination E4/DRSP has a more favourable environmental profile than EE2/DRSP.

Triclosan, an antimicrobial drug, induced reproductive impairment in the freshwater fish, Anabas testudineus (Bloch, 1792)

Triclosan (TCS), an antimicrobial drug, is known to occupy different compartments in aquatic ecosystems. The present study focused to evaluate the reproductive toxicity of triclosan, at environmentally relevant (0.009 and 9 μg L-1) and sublethal (176.7 μg L-1) concentrations for 90 days in the pre-spawning phase of the fish, Anabas testudineus. The reproductive biomarkers, namely, gonadal steroidogenic enzymes, expression of aromatic genes, levels of serum gonadotropins, sex hormones, and histology of gonads were analyzed. The weight of the animal, brain weights along with gonadosomatic index decreased while mucus deposition increased significantly at all concentrations of triclosan as the primary defensive mechanism to prevent the entry of toxicants. Triclosan disrupted gonadal steroidogenesis as evidenced by a reduction in the activities of gonadal steroidogenic enzymes. The expressions of cyp19a1a and cyp19a1b genes were up-regulated in the brain of both sexes and testis, while down-regulated in the ovary indicating estrogenic effects of the compound. The endocrine-disrupting effects of triclosan were confirmed. The current results suggest that chronic exposure to triclosan altered reproductive endpoints thereby impairing normal reproductive functions in fish.

Dose addition in mixtures of compounds with dissimilar endocrine modes of action in in vitro receptor activation assays and the zebrafish sexual development test

BACKGROUND

Human exposure to pesticides is being associated with feminisation for which a decrease of the anogenital distance (AGD) is a sensitive endpoint. Dose addition for the cumulative risk assessment of pesticides in food is considered sufficiently conservative for combinations of compounds with both similar and dissimilar modes of action (MoA).

OBJECTIVE

The present study was designed to test the dose addition hypothesis in a binary mixture of endocrine active compounds with a dissimilar mode of action for the endpoint feminisation.

METHODS

Compounds were selected from a list of chemicals of which exposure is related to a decrease of the AGD in rats and completed with reference compounds. These chemicals were characterised using specific in vitro transcriptional activation (TA) assays for estrogenic and androgenic properties, leading to a final selection of dienestrol as an ER-agonist and flutamide, linuron, and deltamethrin as AR-antagonists. These compounds were then tested in an in vivo model, i.e. in zebrafish (Danio rerio), using sex ratio in the population as an endpoint in order to confirm their feminising effect and MoA. Ultimately, the fish model was used to test a binary mixture of flutamide and dienestrol.

RESULTS

Statistical analysis of the binary mixture of flutamide and dienestrol in the fish sexual development tests (FSDT) with zebrafish supported dose addition.

The Distribution Characteristics and Ecological Risks of Alkylphenols and the Relationships between Alkylphenols and Different Types of Land Use

In this study, the spatial distribution characteristics of nine alkylphenols (APs) in the Yongding River and Beiyun River were analyzed. The differences in the concentrations and spatial distribution patterns of nine APs were systematically evaluated using principal component analysis (PCA). The relationships between the concentration distribution patterns and the risks associated with nine APs were investigated under various categories of land use conditions in the region. The results demonstrated that the APs were widely present in both rivers, and the pollution risks associated with the APs were more severe in the Yongding River than in the Beiyun River. The results show that the contamination risks associated with 4-NP were the most serious in the two rivers, with detection percentages of 100% and 96.3%, respectively. In the Yongding River, the APs showed a tendency of low concentration levels in the upper reaches and high levels in the middle and lower regions. Meanwhile, the overall concentration levels of the APs in the Beiyun River were relatively high. However, despite the differences between the upper and middle regions of the Yongding River, the distribution pattern of the APs in the Beiyun River was basically stable. The concentration levels and risk quotient of the APs were negatively correlated with the vegetation cover land use type and positively correlated with the cropland and unused land use types within 500 m, 1 km, and 2 km. The purpose of this study was to provide theoretical data support and a basis for AP pollution risk evaluations in the Yongding River and Beiyun River.

Estrogenic and non-estrogenic effects of bisphenol A and its action mechanism in the zebrafish model: An overview of the past two decades of work

Bisphenol A (BPA) is the most simple and predominant component of the Bisphenol family. BPA is widely present in the environment and the human body as a result of its extensive usage in the plastic and epoxy resins of consumer goods like water bottles, food containers, and tableware. Since the 1930s, when BPA's estrogenic activity was first observed, and it was labeled as a "mimic hormone of E2", studies on the endocrine-disrupting effects of BPA then have been widely conducted. As a top vertebrate model for genetic and developmental studies, the zebrafish has caught tremendous attention in the past two decades. By using the zebrafish, the negative effects of BPA either through estrogenic signaling pathways or non-estrogenic signaling pathways were largely found. In this review, we tried to draw a full picture of the current state of knowledge on the estrogenic and non-estrogenic effects of BPA with their mechanisms of action through the zebrafish model of the past two decades, which may help to fully understand the endocrine-disrupting effects of BPA and its action mechanism, and give a direction for the future studies.

Does dietary exposure to 17α-ethinylestradiol alter biomarkers related with endocrine disruption and oxidative stress in the adult triploid of Danio rerio?

This study was conducted to investigate a comprehensive effect of 17α-ethinylestradiol (EE2) in zebrafish (Danio rerio) with the emphasis on endocrine disruption, oxidative stress and detoxification processes at different levels. Adult male triploid zebrafish were exposed to EE2 administered in feed at two concentrations - 10 and 1000 μg/kg for six weeks. The estrogenic potential of EE2 was evaluated using an analysis of vitellogenin, gene expression focused on reproductive disorders and gonad histological examination. The alterations in antioxidant and detoxification status were assessed using analyses of enzyme activities and changes in transcriptional levels of selected genes. The most significant changes were observed especially in fish exposed to a high concentration of EE2 (i.e., 1000 μg/kg). Such high concentration caused extensive mortality (25 %) mainly in the second half of the experiment followed by a highly significant decrease in the length and body weight. Similarly, highly significant induction of vitellogenin level and vtg1 mRNA expression (about 43,000-fold compared to the control) as well as a significant downregulation of gonad aromatase expression (cyp19a1a) and histological changes in testicular tissue were confirmed in this group. In the group exposed to environmentally relevant concentration of EE2 (i.e., 10 μg/kg), no significant differences in vitellogenin were observed, although all fish were positive in the detection of vitellogenin compared to control, where only 40 % of individuals were positive. In addition, the high concentration of EE2 resulted in significant alterations in most monitored antioxidant and detoxifying enzymes with the exception of catalase, followed by strongly significant upregulation in mRNA expression of gsr, gpx1a, cat and cyp1a genes. Furthermore, a significant decrease in the glutathione reductase activity was recorded in fish exposed to 10 μg EE2/kg. To our knowledge, this is the first study which reports the effects of subchronic per oral exposure to EE2 in adult triploid zebrafish.

A QSAR-ICE-SSD model prediction of the PNECs for alkylphenol substances and application in ecological risk assessment for rivers of a megacity

Alkylphenols (APs) are ubiquitous and generally present in higher residue levels in the environment. The present work focuses on the development of a set of in silico models to predict the aquatic toxicity of APs with incomplete/unknown toxicity data in aquatic environments. To achieve this, a QSAR-ICE-SSD model was constructed for aquatic organisms by combining quantitative structure-activity relationship (QSAR), interspecies correlation estimation (ICE), and species sensitivity distribution (SSD) models in order to obtain the hazardous concentrations (HCs) of selected APs. The research indicated that the keywords "alkylphenol" and "nonylphenol" were most commonly studied. The selected ICE models were robust (R2: 0.70-0.99; p-value < 0.01). All models had a high reliability cross- validation success rates (>75%), and the HC5 predicted with the QSAR-ICE-SSD model was 2-fold than that derived with measured experimental data. The HC5 values demonstrated nearly linear decreasing trend from 2-MP to 4-HTP, while the decreasing trend from 4-HTP to 4-DP became shallower, indicates that the toxicity of APs to aquatic organisms increases with the addition of alkyl carbon chain lengths. The ecological risks assessment (ERA) of APs revealed that aquatic organisms were at risk from exposure to 4-NP at most river stations (the highest risk quotient (RQ) = 1.51), with the highest relative risk associated with 2.9% of 4-NP detected in 82.9% of the sampling sites. The targeted APs posed potential ecological risks in the Yongding and Beiyun River according to the mixture ERA. The potential application of QSAR-ICE-SSD models could satisfy the immediate needs for HC5 derivations without the need for additional in vivo testing.

Gene Expression of Takifugu rubripes Gonads During AI- or MT-induced Masculinization and E2-induced Feminization

Elucidating the global molecular changes that occur during aromatase inhibitor (AI)- or 17α-methyltestosterone (MT)-induced masculinization and estradiol-17β (E2)-induced feminization is critical to understanding the roles that endocrine and genetic factors play in regulating the process of sex differentiation in fish. Here, fugu larvae were treated with AI (letrozole), MT, or E2 from 25 to 80 days after hatching (dah), and gonadal transcriptomic analysis at 80 dah was performed. The expression of dmrt1, gsdf, foxl2, and other key genes (star, hsd3b1, cyp11c1, cyp19a1a, etc.) involved in the steroid hormone biosynthesis pathway were found be altered. The expression of dmrt1, gsdf, cyp19a1a, and foxl2 was further verified by quantitative polymerase chain reaction. In the control group, the expression of dmrt1 and gsdf was significantly higher in XY larvae than in XX larvae, while the expression of foxl2 and cyp19a1a was significantly higher in XX larvae than in XY larvae (P < .05). AI treatment suppressed the expression of foxl2 and cyp19a1a, and induced the expression of dmrt1 and gsdf in XX larvae. MT treatment suppressed the expression of foxl2, cyp19a1a, dmrt1, and gsdf in XX larvae. E2 treatment suppressed the expression of dmrt1 and gsdf, but did not restore the expression of foxl2 and cyp19a1a in XY larvae. The shared response following AI, MT, and E2 treatment suggested that these genes are essential for sex differentiation. This finding offers some insight into AI or MT-induced masculinization, and E2-induced femininization in fugu.

Pollution characteristics and mixture risk prediction of phenolic environmental estrogens in rivers of the Beijing-Tianjin-Hebei urban agglomeration, China

Phenolic environmental estrogens (PEEs) are ubiquitous in most rivers worldwide and may cause potential endocrine-disrupting effects in aquatic organisms. Three typical PEEs (bisphenol A, BPA; 4-tert-octylphenol,4-t-OP; and nonylphenol, NP) were investigated in the rivers of the Beijing-Tianjin-Hebei urban agglomeration, which is the most urbanized and industrialized area in North China. The target PEEs were detected in 100% of river water samples, and the concentrations ranged from 23 to 255 ng L^-1. The concentrations of NP in most river sections were higher than those of BPA and 4-t-OP. The spatiotemporal variations in PEEs indicated that both domestic and industrial wastewater were main sources of PEEs in river water. In addition, rainfall runoff might be an important source of PEEs in the receiving waters, especially in the wet season. The ecotoxicological risk assessment of individual PEE revealed a moderate to high risk for aquatic organisms at most sampling sites. The mixture risk prediction based on the concentration addition method indicated a potential cumulative risk of PEEs in the study area, highlighting the importance of mixture risk assessment in the aquatic environment.

Roles of Estrogens in the Healthy and Diseased Oviparous Vertebrate Liver

The liver is a vital organ that sustains multiple functions beneficial for the whole organism. It is sexually dimorphic, presenting sex-biased gene expression with implications for the phenotypic differences between males and females. Estrogens are involved in this sex dimorphism and their actions in the liver of several reptiles, fishes, amphibians, and birds are discussed. The liver participates in reproduction by producing vitellogenins (yolk proteins) and eggshell proteins under the control of estrogens that act via two types of receptors active either mainly in the cell nucleus (ESR) or the cell membrane (GPER1). Estrogens also control hepatic lipid and lipoprotein metabolisms, with a triglyceride carrier role for VLDL from the liver to the ovaries during oogenesis. Moreover, the activation of the vitellogenin genes is used as a robust biomarker for exposure to xenoestrogens. In the context of liver diseases, high plasma estrogen levels are observed in fatty liver hemorrhagic syndrome (FLHS) in chicken implicating estrogens in the disease progression. Fishes are also used to investigate liver diseases, including models generated by mutation and transgenesis. In conclusion, studies on the roles of estrogens in the non-mammalian oviparous vertebrate liver have contributed enormously to unveil hormone-dependent physiological and physiopathological processes.

Ethinylestradiol (EE2) residues from birth control pills impair nervous system development and swimming behavior of zebrafish larvae

The ubiquitous use of ethinylestradiol (EE2), an active constituent of birth control preparations, results in continuous release of this synthetic estrogen to surface waters. Many studies document the untoward effects of EE2 on the endocrine system of aquatic organisms. Effects of environmental EE2 on the nervous system are still poorly documented. We studied effects of pico- to nanomolar concentrations of EE2 on early nervous system development of zebrafish larvae. EE2 disrupted axonal nerve regeneration and hair cell regeneration up to 50%. Gene expression in larval brain tissues showed significantly upregulated expression of target genes, such as estrogen and progesterone receptors, and aromatase B. In contrast, downregulation of the tyrosine hydroxylase, involved in the synthesis of neurotransmitters, occurred concomitant with diminution of proliferating cells. Overall, the size of exposed fish larvae decreased by 25% and their swimming behavior was modified compared to non-treated larvae. EE2 interferes with nervous system development, both centrally and peripherally, with negative effects on regeneration and swimming behavior. Survival of fish and other aquatic species may be at risk in chronically EE2-contaminated environments.

Molecular mechanism of reproductive toxicity induced by beta-cypermethrin in zebrafish

Beta-cypermethrin, a type II synthetic pyrethroid insecticide, is widely used in pest control. Several studies have demonstrated that beta-cypermethrin can affect the reproductive system of mammals. However, there is still a scarcity of information about the reproductive toxicity to fish induced by beta-cypermethrin and its molecular mechanism. Therefore, this study was conducted to address this scientific question, in which the adult zebrafish were exposed to 0 (blank control), 0 (acetone solvent control), 0.1, 0.5, and 2.5 μg/L of beta-cypermethrin for 21 days. A decrease in cumulative egg production of zebrafish was observed, indicating that beta-cypermethrin had a negative impact on reproductive capacity of zebrafish. Regarding the histomorphological analysis of gonads, the delay of gonadal development was observed after exposure for 21 days. In addition, significant changes in plasma 17β-estradiol (E2) and testosterone (T) were found in zebrafish. Further exploration showed that the transcription levels of hypothalamic-pituitary-gonadal (HPG) axis-related genes were remarkably changed, which corresponded well with the alterations of hormone levels. These results demonstrated that beta-cypermethrin might have an adverse effect on the reproduction system of zebrafish through delaying gonadal development, disturbing sex hormone secretion, and affecting HPG axis gene expression. This study suggests that beta-cypermethrin poses a potential threat to the reproduction of fish populations, and the toxicity assessment of beta-cypermethrin plays a vital role in the environmental risk assessment of pesticides.

The Influence of Environmental Factors on Ovarian Function, Follicular Genesis, and Oocyte Quality

Endocrine-disrupting chemicals (EDCs) exist ubiquitously in the environment. Epidemiological data suggest that the increasing prevalence of infertility may be related to the numerous chemicals. Exposure to EDCs may have significant adverse impacts on the reproductive system including fertility, ovarian reserve, and sex steroid hormone levels. This chapter covers the common exposure ways, the origins of EDCs, and their effects on ovarian function, follicular genesis, and oocyte quality. Furthermore, we will review the origin and the physiology of ovarian development, as well as explore the mechanisms in which EDCs act on the ovary from human and animal data. And then, we will focus on the bisphenol A (BPA), which has been shown to reduce fertility and ovarian reserve, as well as disrupt steroidogenesis in animal and human models. Finally, we will discuss the future direction of prevention and solution methods.

Trace determination of eleven natural estrogens and insights from their occurrence in a municipal wastewater treatment plant and river water

As endocrine disruptors, natural estrogens including estrone (E1), 17β-estradiol (E2), and estriol (E3) in wastewaters of municipal wastewater treatment plant (WWTP) as well as other environmental matrix have been widely studied. However, the far-less studied natural estrogens such as 2-hydroxyestrone (2OHE1), 16α-hydroxyestrone (16α-OHE1), 4-hydroxyestrone (4OHE1), etc., found in human urine have been almost ignored. Therefore, it is important to investigate the occurrence of these far-less studied natural estrogens in municipal WWTP and other environment. In this study, a GC-MS analytical method was firstly established and validated for trace determination of eleven natural estrogens in waste and surface waters, including E1, E2, E3, 2OHE1, 16α-OHE1, 4OHE1, 2-hydroxyestradiol (2OHE2), 4-hydroxyestradiol (4OHE2), 17-epiestriol (17epiE3), 16-epiestriol (16epiE3), and 16keto-estradiol (16ketoE2). All the eleven natural estrogens were detected in the influent of one municipal WWTP, which ranged from 7.9 to 62.9 ng/L. The top five natural estrogens in the influent were E1, E3, 16α-OHE1, 16ketoE2, and 2OHE1 with respective concentrations of 62.9, 62.6, 46.9, 32.7, and 28.8 ng/L. Most of them were detected in both the effluent and river water, in which their detected concentrations were n.d-14.7 and n.d-51.7 ng/L, respectively. This work is the first to indicate that the so far less commonly studied natural estrogens in the environment likely pose adverse health effect on humans and wildlife due to their relative strong estrogenic potencies and high levels in wastewater and river water. More work should be done to understand their removals in municipal WWTPs and their occurrence in surface waters.

Chronic exposure of zebrafish (Danio rerio) to flutolanil leads to endocrine disruption and reproductive disorders

The pesticide flutolanil has been detected in fish and aquatic environments, but its potential impact on the endocrine function is unknown. In this study, two-month zebrafish were exposed to the environmentally relevant concentrations of flutolanil for 60 days to examine the reproductive endpoints on the gonad endocrine system. Increased 17 beta-estradiol (17β-E2) content and 17β-E2/T ratio and decreased testosterone (T) in male suggested that flutolanil produces the estrogenic effect. In support of this view, vitellogene (vtg1, vtg2) and cytochrome P450 aromatase 19a (cyp19a) expression were up-regulated in the male liver. The levels of global DNA methylation were increased in ovary. Parental zebrafish exposure to different concentrations of flutolanil affected the offspring development as shown by short body length, and increased mortality. Thus, these results demonstrate that flutolanil exposure results in gonad endocrine disruption, decreased reproduction, and developmental toxicity in F1, highlighting the importance of assessing the potential environmental risks of flutolanil application.

Mummichog (Fundulus heteroclitus) are less sensitive to 17α-ethinylestradiol (EE2) than other common model teleosts: A comparative review of reproductive effects

The environmental estrogen 17α-ethinylestradiol (EE₂) will depress or completely inhibit egg production in many common model teleosts at low concentrations (≤0.5 ng/L; Runnalls et al., 2015). This inhibition is not seen in the estuarine killifish, or mummichog (Fundulus heteroclitus), even when exposed to 100 ng/L EE₂. This relative insensitivity to EE₂ exposure indicates species-specific mechanisms for compensating for exogenous estrogenic exposure. This review compares various reproductive responses elicited by EE₂ in mummichog to other common model teleosts, such as zebrafish (Danio rerio) and fathead minnow (Pimephales promelas), identifying key endpoints where mummichog differ from other studied fish. For example, EE₂ accumulates primarily in the liver/gall bladder of mummichog, which is different than zebrafish and fathead minnow in which accumulation is predominantly in the carcass. Despite causing species-specific differences in fecundity, EE₂ has been shown to consistently induce hepatic vitellogenin in males and cause feminization/sex reversal during gonadal differentiation in larval mummichog, similar to other species. In addition, while gonadal steroidogenesis and plasma steroid levels respond to exogenous EE_2, it is generally at higher concentrations than observed in other species. In mummichog, production of 17β-estradiol (E₂) by full grown ovarian follicles remains high; unlike other teleost models where E₂ synthesis decreases as 17α,20β-dihydroxy-4-prenen-3-on levels increase to induce oocyte maturation. New evidence in mummichog indicates some dissimilarity in gonadal steroidogenic gene expression responses compared to gene expression responses in zebrafish and fathead minnow exposed to EE₂. The role of ovarian physiology continues to warrant investigation regarding the tolerance of mummichog to exogenous EE₂ exposure. Here we present a comprehensive review, highlighting key biological differences in response to EE₂ exposure between mummichog and other commonly used model teleosts.

Transcription pattern of reproduction relevant genes along the brain-pituitary-gonad axis of female, male and intersex thicklip grey mullets, Chelon labrosus, from a polluted harbor

The reproductive cycle of teleost fishes is regulated by the brain-pituitary-gonad (BPG) axis. The transcription profile of genes involved in the reproduction signalling in the BPG-axis differs in females and males during the gametogenic cycle. Impacts of endocrine disrupting chemicals on these signalling pathways in fish are known, but the participation of the BPG-axis in the development of the intersex condition is not well understood. Intersex thicklip grey mullets (Chelon labrosus) have been identified in several estuaries from the SE Bay of Biscay, revealing the presence of feminizing contaminants in the area. In previous studies, transcription patterns of genes related with steroidogenesis and gamete growth have been shown to differ among female, male and intersex mullets. However, many components of the reproduction control have not been studied yet. The aim of this study was to assess the transcription levels of target BPG-axis genes in female, male and intersex mullets captured in the polluted harbour of Pasaia, during their gametogenic cycle. After histologically examining the gonads, the transcription levels of previously sequenced target genes were measured by qPCR: kiss2, gpr54 and gnrh1 in brain, fshβ and lhβ in pituitary and fshr and lhr in gonads. In both females and males, brain genes were most transcribed in early gametogenesis, proving their relevance in the onset of both oogenesis and spermatogenesis. Pituitary gonadotropins in females showed upregulation as oogenesis progressed, reaching the highest transcription levels at vitellogenic stage, while in males transcript levels were constant during spermatogenesis. Transcription levels of gonadotropin receptors showed different patterns in ovaries and testes, suggesting differing function in relation to gametogenesis and maturation. Intersex mullets showed transcription levels of brain target genes similar to those observed in females at cortical alveoli stage and to those in mid spermatogenic males. In intersex testes the transcription pattern of gonadotropin receptor fshr was downregulated in comparison to non-intersex testes.

A T > G Mutation in the NR5A2 Gene Is Associated With Litter Size in Hu Sheep Through Upregulation of Promoter Activity by Transcription Factor MTF-1

Nuclear receptor subfamily 5 group A member 2 (NR5A2), also referred to as LRH-1 or FTF, is an orphan nuclear hormone receptor that is involved in regulating embryonic development, ovarian granulosa cell differentiation, gonadal sex differentiation, and steroidogenesis in mammals. However, little is known about how NR5A2 regulates reproduction in sheep. In this study, we amplified the promoter sequence of NR5A2 and determined that its core promoter region ranged from -721 nt to -281 nt. A T > G polymorphism at -700 nt was detected in the core promoter region. Association analysis found that the litter sizes of Hu ewes at their second and average parities with genotype GG (2.20 ± 0.20 and 1.97 ± 0.06, respectively) were significantly higher than those of ewes with genotype TG (1.68 ± 0.10 and 1.74 ± 0.05, respectively) (p < 0.05) and TT (1.67 ± 0.10 and 1.62 ± 0.06, respectively) (p < 0.05). The litter size of Hu ewes at their third parity with genotype GG (2.10 ± 0.10) was significantly higher than that of ewes with genotype TT (1.56 ± 0.12) (p < 0.05). A luciferase assay showed that the -700G allele increased the luciferase activity relative to the -700T allele. Furthermore, the -700T > G polymorphism created a novel binding site for metal-regulatory transcription factor 1 (MTF-1). A competitive electrophoretic mobility shift assay confirmed that MTF-1 specifically bound with the G-type promoter of NR5A2. An overexpression experiment demonstrated that MTF-1 was involved in the alteration of NR5A2 transcription activity and further increased NR5A2 gene mRNA expression. Our findings revealed that the -700T > G polymorphism promoted NR5A2 expression due to the positive effects on NR5A2 gene transcription activity by MTF-1 and thereby increased fecundity in Hu sheep.

Environmental exposure to oestrogenic endocrine disruptors mixtures reflecting on gonadal sex steroids and gametogenesis of the neotropical fishAstyanax rivularis

Discharge of municipal wastewater promotes the entry of diverse oestrogenic compounds into the water bodies. This complex mixture of substances interferes in the steroidogenic pathway, being able to promote severe reproductive impairment in freshwater fish populations. The purpose of the present study was to evaluate the effects of oestrogenic endocrine disruptors (EDCs) mixture on gonadal sex steroids (testosterone, T; 11-ketotestosterone, 11-KT; 17β-oestradiol, E2; 17-hydroxyprogesterone, 17-OHP) in the peak of the reproductive season of Astyanax rivularis, correlating the results obtained with the proportion of germ cells and gonadal histopathology. Three sampling sites were chosen to conduct the study, one reference site (S1), without contamination by municipal wastewater and two sites (S2 and S3) receiving discharge of municipal wastewater. Males of A. rivularis presented higher concentrations of E2, lower androgens (T and 11-KT) in gonads when compared to males from site S1. Concentrations of 17-OHP did not present significant difference among sites. In sites S2 and S3, the proportion of early spermatocytes, spermatids and Leydig cells increased while spermatozoa decreased compared to fish from S1. The following gonadal histopathologies were detected in the male fishes: intersex gonads (28% in S3) and testicular degeneration with germinal epithelium exhibiting agglutinated germ cells masses and empty cysts (57% in S2 and 71% in S3). In females, concentrations of T, E2 and 17-OHP did not present significant difference among the sites, however higher 11-KT concentrations were detected in females from sites S2 and S3. A lower proportion of perinucleolar follicles and a higher incidence of vitellogenic follicles, besides, aged oocytes and the presence of eosinophilic proteinaceous fluid in the interstitial compartment were also found in females from impacted sites. These results indicate that the urbanization and consequent release of municipal wastewater containing oestrogenic compounds in the headwater creeks are altering the levels of sex hormones and gametogenesis of A. rivularis. Further studies should be performed to determine whether oestrogenic endocrine disrupters are disrupting the reproduction of A. rivularis.

Toxic effects of single animal hormones and their mixtures on the growth of Chlorella vulgaris and Scenedesmus armatus

In their environments, aquatic organisms are simultaneously exposed to mixtures of several endocrine disrupting compounds, including hormones. However, most of the toxicity studies so far focused on effects of single contaminants. The available information on the potential toxicity of combined hormones on microalgae is extremely limited. For these reasons the aim of this study was to evaluate the individual and mixture effect of estrone (E1), ß-estradiol (E2), estriol (E3), 17-α-ethinylestradiol (EE2), progesterone (PRO), 5-pregnen-3β-ol-20-one (PRE), levonorgestrel (LG) and testosterone (TST) on Chlorella vulgaris and Scenedesmus armatus. Green algae cells were exposed to different concentrations (0.1-100 mg L^-1) of hormones for 14 days. Biomass in the form of dry weight and chlorophyll a was examined. The decreasing order of toxicity (based on EC₅₀, 14d) to Chlorella vulgaris and Scenedesmus armatus was: EE2>PRO > E2>PRE > TST > E3>LG > E1 and EE2>PRO > TST > E2>PRE > LG > E1>E3, respectively. Chlorella vulgaris was more sensitive to the effects of hormones than Scenedesmus armatus. Although mixed hormones were more toxic to green algae than single hormones, in the ecosystem mixtures can pose higher ecological risk than single pollutants. Therefore, data on the toxicology of both single and mixed hormones is very valuable for assessment of the possibility of adverse ecological effects caused by these pollutants. Furthermore, these results suggest that environmental exposure to hormone mixtures may cause toxicity levels different to the sum of those of the single hormones and provides a basic understanding of their toxic effect on algae.

Determination and reduced life expectancy model and molecular docking analyses of estrogenic potentials of 17β-estradiol, bisphenol A and nonylphenol on expression of vitellogenin gene (vtg1) in zebrafish

This study determined and evaluated the estrogenic potentials on hepatic vitellogenin gene (vtg1) of adult male zebrafish which were exposed to low level concentrations (ng/L-μg/L levels) of individual and binary mixtures of 17β-estradiol (E₂), bisphenol A (BPA) and nonylphenol (NP) through the use of reduced life expectancy (RLE) model and molecular docking analysis. The order of in vivo estrogenic potentials of individual and binary exposure of E₂, BPA and NP was as follows: E₂+BPA＞E₂＞E₂+NP＞BPA＞BPA + NP >>>NP. Binary mixtures of E₂, BPA and NP had weak synergistic effects under the exposure concentration ranges. With the expression of hepatic vtg1 gene, the hepatic toxicity was analyzed by using the RLE model. All plots of the linear RLE model had negative slopes indicating that EC₅₀ was negatively correlated with the natural logarithm of exposure time (lnET₅₀). The RLE model analyses can be useful to evaluate the exposure time effects of zebrafish by using EC₅₀ as toxicity endpoint. Molecular docking analysis revealed that the interaction potential of E₂ (Binding energy: -10.1 kcal/mol) for the zebrafish ERα-LBD was the most potent (stable), followed by BPA (-8.0 kcal/mol) and NP (-6.8 kcal/mol). Molecular docking analysis can be useful to understand interactive effects of E₂, BPA and NP.

Toxicity effects of the organic UV-filter 4-Methylbenzylidene camphor in zebrafish embryos

Ultraviolet (UV) filters are widely used in personal care products and due to their lipophilicity these chemicals tend to bioaccumulate in the aquatic biota. 4-Methylbenzylidene camphor (4-MBC) is one of the most used UV-filters, and it is commonly detected in freshwater fish tissues. This substance is suspected to be an endocrine disruptor due to its interaction with Hypothalamus-Pituitary-Gonadal (HPG) and HP-Thyroid (HPT)-axis. The main objective of this study was to evaluate the effects of 4-MBC on apical endpoints, biochemical markers and on genes involved in endocrine pathways in Danio rerio. Zebrafish embryos were exposed to 4-MBC (0.083-0.77 mg/l) from 0 to 96 h post-fertilization (hpf). Hatching, heart rate and malformations were the apical endpoints assessed. Alterations on neurotransmission and oxidative stress were evaluated through acetylcholinesterase (AChE), catalase (CAT) and glutathione S-transferase (GST) enzymatic activities. Endocrine effects were analysed by the expression of genes involved in HPG and HPT-axis of embryos exposed 96 h to the EC₁₀ of 4-MBC (0.19 mg/l). Exposure to 4-MBC induced morphological abnormalities during embryonic development, including notochord curvature, delayed absorption of yolk sac and pericardial oedema. Concentration of 0.77 mg/l 4-MBC decreased embryo heart rate at 48h. At neurotransmission level, an induction of AChE at concentrations above 0.15 mg/l was observed. Malformations and decreased heart rate along with alterations observed at neurotransmission level might have compromised zebrafish larvae equilibrium. Glutathione S-transferase induction above 0.15 mg/l 4-MBC suggests activation of detoxification processes. Furthermore, observed brain aromatase gene down-regulation by 4-MBC suggests impairment of normal functioning of HPG axis in zebrafish.

Long-term exposure of xenoestrogens with environmental relevant concentrations disrupted spermatogenesis of zebrafish through altering sex hormone balance, stimulating germ cell proliferation, meiosis and enhancing apoptosis

Environmental estrogens are capable of interfering with the spermatogenesis and fertility of fish. However in natural waters, these chemicals are more likely to occur as a combination rather than a single stressor. Whether and how the mixture of xenoestrogens with environmental relevant concentrations may affect fish spermatogenesis remains largely unknown. In this study, male zebrafish adults were administered to 17alpha-ethinylestradiol (EE2) and a mixture of xenoestrogens (Mix (E2, EE2, DES, 4-t-OP, 4-NP and BPA)), with the estrogenic potency equivalent to EE2. After a 60-day exposures, elevated mRNA levels of vitellogenin 1 (vtg1) and estrogen receptor 1 (esr1) in the liver of fish in both treated groups were observed. Moreover, the plasma level of E2 declined significantly in the Mix group and the ratio of 11-KT/E2 was significantly elevated in both treated groups. Consistently, the mRNA level of P450 side-chain cleavage (scc) in the EE2 group and ovarian type aromatase (cyp19a1a) in the Mix group was significantly suppressed. In addition, decreased gonadosomatic index and sperm count in the fish of Mix group were present. Furthermore, increased number of the proliferating germ cells (such as spermatogonia and spermatocytes) was observed in the fish of both groups, suggesting a stimulated germ cell proliferation and meiosis. Accordingly, both exposures significantly up-regulated the mRNA levels of genes in mitosis (cyclinb1) and meiosis (cyp26a1 in EE2 group, aldh1a2, cyp26a1, sycp3 and spo11 in Mix). In addition, decreased number of spermatozoa and increased number of TUNEL-positive signals were present in the testis of fish in the Mix group, indicating an enhanced apoptosis. Further analyses demonstrated the significant elevated expressions of tnfrsf1a and the ratio of tnfrsf1a/tnfrsf1b in the Mix group, suggesting an elevated apoptosis in the testis of fish in the Mix group via extrinsic pathway. The present study greatly extends our understanding of the underlying mechanisms of the reproductive toxicity of xenoestrogens on fish.

The intersex phenomenon in Sarotherodon melanotheron from Lagos lagoon (Nigeria): Occurrence and severity in relation to contaminants burden in sediment

The correlation between endocrine active contaminants in the environment and alterations in reproductive development of Sarotherodon melanotheron from Lagos lagoon has been investigated. Sediment and a total of 155 fish (74 males and 81 females) were collected between November 2014-March 2015 from selected contaminated sites (Ikorodu, Oworonshoki, Makoko and Idumota) and a putative control site (Igbore) along the lagoon. Sediment contaminant analysis revealed, significantly higher concentration of lindane, dieldrin, 4-iso-nonylphenol, 4-t-octylphenol and monobutyltin cation at the contaminated sites. Examination of gross morphological and histological changes of fish gonads showed a 27.4% prevalence of intersex in the sampled fish, of which 78% were males (testes-ova) and 22% were females (ovo-testis). Quantitative PCR (qPCR) of liver transcripts revealed the presence of vitellogenin (vtg) levels in male fish from contaminated sites. Zona radiata proteins (zrp) mRNA levels were significantly higher in females, compared to male fish. In general, significantly lower vtg and zrp transcripts levels were recorded at Igbore (control site), compared with contaminated sites. Principal component analysis (PCA) showed site and sex relationship in biological responses and contaminants, including trace metals, demonstrating that measured endocrine responses in fish were associated with contaminant burden in sediment. In addition, positive relationships were observed in male fish from Idumota, Oworonshoki and Ikorodu with vtg and dieldrin/4-iso-nonyphenol, with higher levels in male fish, compared to females. Further, contaminants from the Makoko, Oworonshoki and Ikorodu sites were positively associated with higher GSI and zrp in females. More importantly, the severity of intersex and changes in vtg transcripts imply a progressive feminization of male fish with concomitant alteration in the reproductive health of fish inhabiting the Lagos lagoon.

Parental transfer of ethylhexyl methoxy cinnamate and induced biochemical responses in zebrafish

Ethylhexyl methoxy cinnamate (EHMC) is one of the major organic ultraviolet (UV) filter pollutants in the environment. The purpose of this study was to investigate the parental transfer of EHMC and induced biochemical responses in zebrafish (Danio rerio). Zebrafish embryos were exposed to EHMC solution (1, 10, and 100 μg/L) for 4 months until sexual maturation. Then male and female parents were paired to lay eggs. F1 generations were divided into 2 categories: with and without continued EHMC exposure. EHMC was detected in both F0 parents and F1 eggs, indicating that EHMC can accumulate in zebrafish and transfer to offspring through reproduction. The hatching rate decreased and malformation rate increased significantly among parents and progeny embryos in the high concentration exposure group. For 40 dpf (days post-fertilisation) F0 generations, estradiol hormone and vitellogenin (Vtg) contents, the expression levels of Vtg1, P450 aromatase (Cyp19a and Cyp19b), 17β-hydroxysteroid dehydrogenase (Hsd17b1, Hsd17b3), estrogen receptor-alpha and progesterone receptor in all concentration groups decreased significantly, while androgen receptor increased significantly in 10 and 100 μg/L exposure groups compared with the corresponding control group, showing anti-estrogen and androgen effects. For 120 dpf F0 generations, acetylcholinesterase activity was significantly decreased and glutathione and malondialdehyde levels, superoxide dismutase, catalase and glutathione reductase activities were significantly increased in all treatment groups compared with the corresponding control group. In addition, F1 offspring with or without continued exposure to EHMC suffered similar or stronger oxidative stress compared with their parents. DNA breakage and apoptosis also occurred in 120 dpf parental liver cells in all treatment groups as a result of oxidative damage. Results suggested that EHMC have transfer effects between parents and offspring, which may cause negative effects on growth and development of zebrafish and induce biochemical responses in both parents and offspring.

Mycotoxin zearalenone induced gonadal impairment and altered gene expression in the hypothalamic-pituitary-gonadal axis of adult female zebrafish (Danio rerio)

In the present study, we aimed to assess the adverse effects of zearalenone (ZEA) at environmentally relevant concentrations (0.5, 1, 5 and 10 μg l^-1 ) on hypothalamic-pituitary-gonadal axis associated reproductive function using zebrafish model. ZEA was exposed to female zebrafish for 21 days to assess growth indices such as condition factor, hepatosomatic index, gonadosomatic index and caspase 3 activity. Further, expression of estrogen receptor (ER) α and CYP19a1b genes in the brain, ERα and vitellogenin (Vtg) genes in the liver and follicle-stimulating hormone receptor, luteinizing hormone receptor, ERα, steroidogenic acute regulatory protein, 3β-hydroxysteroid dehydrogenase (HSD), 17-βHSD and CYP19a1 genes in the ovary were also investigated. Our results showed that there were no significant changes in the condition factor and hepatosomatic index, whereas a significant (P < .05) reduction in the gonadosomatic index, increase in caspase 3 activities and Vtg expression was observed at higher concentration. However, no significant changes were observed at lower treatment levels. Further, we also observed significant (P < .05) upregulation in ERα, Vtg, luteinizing hormone receptor, steroidogenic acute regulatory protein, 3β-HSD, 17β-HSD, CYP19a1 and CYP19a1b genes in treatment groups with higher levels of ZEA. Moreover, in histopathological examination, we observed oocyte atresia and oocyte membrane detachment in ovaries at the highest concentration. In conclusion, the present study revealed the negative impact of ZEA on zebrafish reproductive system by involvement of the hypothalamic-pituitary-gonadal axis-associated reproductive function.

Effects of the bioconcentration and parental transfer of environmentally relevant concentrations of difenoconazole on endocrine disruption in zebrafish (Danio rerio)

Difenoconazole, a typical triazole fungicide, inhibits lanosterol-14R-demethylase (CYP51) to prevent fungal sterol synthesis and its residues are frequently detected in the environment due to its wide application. Previous studies have demonstrated that difenoconazole altered the triglyceride levels, and gene expression relevant to cholesterol biosynthesis in zebrafish. However, endocrine-disruption in the hypothalamus-pituitary-gonadal-liver (HPGL) axis, the effects of transferring to offspring, and the underlying mechanisms of difenoconazole in aquatic organisms are still unknown. In this study, we defined the effects of difenoconazole at environmental concentrations on endocrine disturbance using zebrafish as an experimental model. The results indicated that difenoconazole induced a significant change in the somatic index, and pathological variations in tissues, and steroid hormone levels. RT-PCR experiments further confirmed that difenoconazole significantly induced expression alteration of lhr, hsd3β, hsd11β, cyp19a in the ovary and star, cyp19a, cyp3c1 in the testis, and erα genes in livers. In addition, difenoconazole exposure in parental zebrafish affected the hatchability and length of its offspring. Moreover, the burdens of difenoconazole and difenoconazole alcohol in females were higher than in males. These findings highlighted that difenoconazole exposure at environmentally relevant concentrations elicited estrogenic endocrine-disruption effects via altering homeostasis of sex steroid hormones in the HPGL axis and the adverse effects can be transferred to the offspring.

Effects of triclosan (TCS) on hormonal balance and genes of hypothalamus-pituitary- gonad axis of juvenile male Yellow River carp (Cyprinus carpio)

Triclosan (TCS) is a broad spectrum antimicrobial agent which has been widely dispersed and determinated in the aquatic environment. However, the effects of TCS on reproductive endocrine in male fish are poorly understood. In this study, male Yellow River carp (Cyprinus carpio) were exposed to 0, 1/5, 1/10 and 1/20 LC₅₀ (96 h LC₅₀ of TCS to carp) TCS under semi-static conditions for 42 d. Vitellogenin (Vtg), 17β-estradiol (E₂), testosterone(T), gonadotropin (GtH), and gonadotropin-releasing hormone (GnRH) levels were measured by enzyme-linked immunosorbent assay (ELISA). Meanwhile, we also examined the mRNA expressions of aromatase, GtHs-β, GnRH, estrogen receptor (Er), and androgen receptor (Ar) by quantitative Real-time Polymerase Chain Reaction (qRT-PCR). TCS induced Vtg levels of hepatopancreas, E₂ levels of serum, and inhibited Ar and Er mRNA levels, suggesting that the induction of Vtg production by TCS was indirectly caused by non-Er pathways. TCS-induced Vtg levels by interfering with the reproductive axis at plenty of latent loci of male carps: (a) TCS exposure increased the aromatase mRNA expression of hypothalamus and gonad aromatase, consequently increasing serum concentrations of E₂ to induce Vtg in hepatopancreas; (b) TCS treatment changed GtH-β and GnRH mRNA expression and secretion, causing the disturbance of reproductive endocrine; (c) TCS exposure decreased Ar mRNA levels, indicating potential Ar-mediated antiandrogen action. These mechanisms showed that TCS may induce Vtg production in male carp by non-Er-mediated pathways.

Environmental pollution affects molecular and biochemical responses during gonadal maturation of Astyanax fasciatus (Teleostei: Characiformes: Characidae)

Endocrine disrupting compounds (EDCs) have the potential to alter fish reproduction at various levels of organization. The aim of this study was to assess the impact of a natural environment with heavily anthropogenic influence on the physiological processes involved in reproduction in the freshwater fish lambari (Astyanax fasciatus) using different biomarkers. Adult males and females were collected in different seasons from two distinct sites in the same watershed: Ponte Nova Reservoir (PN) considered a pristine or small anthropogenic influence reference point; and Billings Reservoir (Bil), subjected to a large anthropogenic impact. Biological indices, such as hepatosomatic index and gonadosomatic index (GSI), gonadal histomorphology, fecundity, and biomarkers such as plasma levels of estradiol (E2) as well as hepatic gene expression of its alfa nuclear receptor (ERα), were analyzed. Hepatic vitellogenin (VTG) gene expression was evaluated in both sexes, as an indicator of xenoestrogen exposure. Females collected at PN presented a typical annual variation reflected in GSI, whereas for those sampled at Bil the index did not change through the seasons. The higher concentration of E2 in males collected at Bil during spring/2013, together with the detection of VTG gene expression, suggest the presence of EDCs in the water. These EDCs may have also influenced fecundity of females from Bil, which was higher during winter and spring/2013. Gene expression of ERα and ovarian morphology did not differ between fish from both sites. Water conditions from Bil reservoir impacted by anthropic activity clearly interfered mainly with biomarkers of biological effect such as plasma E2 levels and absolute and relative fecundity, but also altered biomarkers of exposure as VTG gene expression. These facts support the notion that waterborne EDCs are capable of causing estrogenic activity in A. fasciatus.

Endocrine and physiological effects of linuron and S-metolachlor in zebrafish developing embryos

Evaluation of the effects of linuron and S-metolachlor on apical, biochemical and transcriptional endpoints in zebrafish (Danio rerio) early life stages was the main purpose of this work. Embryos were exposed for 96h to a range of concentrations of each herbicide to determine lethal and sub-lethal effects on apical (e.g. malformations, hatching) and biochemical parameters (cholinesterase, ChE; catalase, CAT; glutathione S-transferase, GST; lipid peroxidation, LPO and lactate dehydrogenase, LDH). To evaluate endocrine disruption effects, embryos were exposed during 96h to 0.88mg/L linuron and 9.66mg/L S-metolachlor, isolated or in binary mixture. Expression of a suite of genes involved in HPT, HPG and HPA-axis was then assessed. Highest concentration of linuron (5.0mg/L) decreased hatching rate to 5% and 70.0mg/L S-metolachlor completely inhibited hatching, about 100%. Both herbicides impaired development by inducing several malformations (100% in 5.0mg/L linuron and 70.0mg/L S-metolachlor). Linuron only affected GST and CAT at concentrations of 0.25 and 0.0025mg/L, respectively. S-metolachlor induced GST (to 256%), inhibited ChE (to 61%) and LDH (to 60%) and reduced LPO levels (to 63%). Linuron isolated treatment seems to have an estrogenic mode of action due to the observed induction of vtg1. Exposure to S-metolachlor seems to interfere with steroidogenesis and with HPT and HPA-axis, since it has inhibited cyp19a2, TSHβ and CRH gene expression. In addition to vtg1 induction and CRH inhibition, herbicide combination also induced sox9b that has a role in regulation of sexual development in zebrafish. This study pointed out adverse effects of linuron and S-metolachlor, namely impairment of neurotransmission and energy production, induction of steroidogenesis, and interference with HPT and HPA-axis. These results contributed to elucidate modes of action of linuron and S-metolachlor in zebrafish embryo model. Furthermore, gene expression patterns obtained are indicative of endocrine disruption action of these herbicides.

Alteration in molecular markers of oocyte development and intersex condition in mullets impacted by wastewater treatment plant effluents

Wastewater Treatment Plant (WWTP) discharges are an important source of endocrine disrupting chemicals (EDCs) into the aquatic environment. Fish populations inhabiting downstream of WWTP effluents show alterations in gonad and gamete development such as intersex condition, together with xenoestrogenic effects such as vitellogenin up-regulation. However, the molecular mechanisms participating in the development of intersex condition in fish are not elucidated. The aim of this study was to assess the impact of two WWTPs effluents (Gernika and Bilbao-Galindo situated in the South East Bay of Biscay) with different contaminant loads, in thicklip grey mullet (Chelon labrosus) populations inhabiting downstream, examining the presence and severity of intersex condition, during two seasons. Molecular markers of xenoestrogenicity and oocyte differentiation and development (vtgAa, cyp19a1a, cyp19a1b, cyp11b, foxl2, dmrt1 and gtf3a) were also studied. Intersex mullets were identified downstream of both WWTPs and vtgAa was upregulated in intersex and non intersex males. Sex dependent differential transcription levels of target genes were detected in mullets from Galindo. However, no such pattern was observed in mullets from Gernika, suggesting an attenuating effect over studied genes caused by a higher presence of EDCs in this site, as indicated by the elevated prevalence of intersex mullets in this population. In conclusion, no direct association between xenoestrogenic responses and intersex condition was established. Mullets from Gernika showed signs of severe EDC exposure compared to those from Galindo, as demonstrated by the higher prevalence of intersex males and the reduction in transcription profile differences between sexes of gametogenic gene markers.

Do estrogenic compounds in drinking water migrating from plastic pipe distribution system pose adverse effects to human? An analysis of scientific literature

With the widespread application of plastic pipes in drinking water distribution system, the effects of various leachable organic chemicals have been investigated and their occurrence in drinking water supplies is monitored. Most studies focus on the odor problems these substances may cause. This study investigates the potential endocrine disrupting effects of the migrating compound 2,4-di-tert-butylphenol (2,4-d-t-BP). The summarized results show that the migration of 2,4-d-t-BP from plastic pipes could result in chronic exposure and the migration levels varied greatly among different plastic pipe materials and manufacturing brands. Based on estrogen equivalent (EEQ), the migrating levels of the leachable compound 2,4-d-t-BP in most plastic pipes were relative low. However, the EEQ levels in drinking water migrating from four out of 15 pipes may pose significant adverse effects. With the increasingly strict requirements on regulation of drinking water quality, these results indicate that some drinking water transported with plastic pipes may not be safe for human consumption due to the occurrence of 2,4-d-t-BP. Moreover, 2,4-d-t-BP is not the only plastic pipe-migrating estrogenic compound, other compounds such as 2-tert-butylphenol (2-t-BP), 4-tert-butylphenol (4-t-BP), and others may also be leachable from plastic pipes.

Development and recovery of histopathological alterations in the gonads of zebrafish (Danio rerio) after single and combined exposure to endocrine disruptors (17α-ethinylestradiol and fadrozole)

Exposure of wildlife to endocrine disrupting chemicals (EDCs) is not necessarily continuous. Due to seasonal changes and variable industrial and agricultural activities it often occurs intermittently. Thus, it is possible that aquatic organisms may be more affected by periodic peak exposure than by chronic exposure. Therefore, an experimental scenario including an exposure from 2h to 90 days post-fertilization (dpf) and a subsequent recovery period until 150 dpf was chosen to assess the potential reversibility of the effects of sex steroids on sexual and gonad development of zebrafish (Danio rerio). The aim of this study was to investigate the persistence of the endocrine effects of an estrogen (EE2-17α-ethinylestradiol, 4ng/L), an inhibitor of estrogen synthesis (Fad-fadrozole, 50μg/L) or their binary mixture (Mix-EE2+ Fad, 4ng/L+50μg/L). Afterwards, a semi-quantitative histological assessment was used to investigate histopathological changes on gonad differentiation and development. The data showed that fadrozole, alone or in combination with EE2, permanently disrupts the sexual development, inducing masculinization and causing severe pathological alterations in testis, such as intersex associated to the enlargement of sperm ducts, interstitial changes, asynchronous development and detachment of basal membrane. After exposures to both EDCs and their mixture, the gonad histopathology revealed interstitial proteinaceous fluid deposits and, in ovaries, there were atretic oocytes, and presumably degenerative mineralization. On the other hand, the gonadal changes induced by EE2 alone seem to be partially reversible when the exposure regime changed to a recovery period. In addition, EE2 enhanced zebrafish growth in both genders, with male fish presenting signs of early obesity such as the presence of adipocytes in testis. Moreover, sex ratio was slightly skewed toward females, at 90 and 105 dpf, in zebrafish exposed to EE2. The data further indicate that long-term studies on impacts of single EDCs and their mixtures with recovery periods are crucial to reveal the possibility of sex reversal and pathological changes of gonads that can adversely affect breeding.

Pollution by oestrogenic endocrine disruptors and β-sitosterol in a south-western European river (Mira, Portugal)

The Mira River is a Portuguese water body widely known for its wilderness and is advertised as one of the less polluted European rivers. On this presumption, the levels of endocrine-disrupting compounds (EDCs) in Mira waters were never measured. However, because environmentalists have claimed that the Mira could be moderately polluted, a range of 17 EDCs were measured not only at the estuary but also along the river. The targeted EDCs included natural and pharmaceutical oestrogens (17β-oestradiol, oestrone and 17α-ethynylestradiol), industrial/household pollutants (octylphenols, nonylphenols and their monoethoxylates and diethoxylates and bisphenol A), phytoestrogens (formononetin, biochanin A, daidzein, genistein) and the phytosterol sitosterol (SITO). For this propose, waters from six sampling sites were taken every 2 months, over a 1-year period (2011), and analysed by gas chromatography-mass spectrometry. Unexpectedly high levels of oestrogens and of industrial/household pollutants were measured at all sampling sites, including those located inside natural protected areas. Indeed, the annual average sum of EDCs was ≈57 ng/L for oestrogens and ≈1.3 μg/L for industrial/household chemicals. In contrast, the global average levels of phytoestrogens (≈140 ng/L) and of SITO (≈295 ng/L) were lower than those reported worldwide. The EDC concentrations were normalised for ethynylestradiol equivalents (EE2eq). In view of these, the oestrogenic load of the Mira River attained ≈47 ng/L EE2eq. In addition, phosphates were above legal limits at both spring and summer (>1 mg/L). Overall, data show EDCs at toxicant relevant levels in the Mira and stress the need to monitor rivers that are allegedly less polluted.

Pollution by endocrine disruptors in a southwest European temperate coastal lagoon (Ria de Aveiro, Portugal)

Ria de Aveiro is a Portuguese lagoon renowned for its ecological and economic importance. Nonetheless, in literature, few data exist about its organic pollution. Accordingly, this study chemically monitored for the first time a series of 17 endocrine disruptor compounds (EDCs). The target EDCs include natural (17β-oestradiol, oestrone) and pharmaceutical (17α-ethynylestradiol) oestrogens, industrial/household xenoestrogenic pollutants (octylphenols, nonylphenols and their mono and diethoxylates and bisphenol A), phytoestrogens (formononetin, biochanin A, daidzein, genistein) and the phytosterol sitosterol (SITO). For the investigation of these EDCs, water samples were taken from eight sampling sites widely spread along the lagoon, at three different occasions in 2011, and analysed by gas chromatography-mass spectrometry. Results not only proved the ubiquitous distribution of all analysed EDCs but revealed that their amounts were extremely high at all sampling sites. The annual average concentrations were ≈ 46 ng/L for oestrogens, ≈ 3962 ng/L for industrial/household chemicals, ≈ 1740 ng/L for phytoestrogens and ≈ 908 ng/L for SITO. Normalising these values in ethynylestradiol equivalents (EE2eq), the oestrogenic load in this lagoon attained ≈ 50 ng/L EE2eq, which is a value well above that known to produce oestrogenic-induced disorders in aquatic fauna. Additionally, phosphate concentrations were also above the legal limits (>1 mg/L). Overall, data show EDCs at toxic relevant levels in the Ria de Aveiro and stress the need to enforce depollution measures in this habitat.

Occurrence of Natural Contaminants of Emerging Concern in the Douro River Estuary, Portugal

Many studies demonstrated the presence of diverse environmental contaminants in the Douro River estuary, such as natural and synthetic estrogens, pharmaceuticals, industrial compounds and pesticides. This estuary is located between two densely populated cities and is highly impacted due to anthropogenic activities, such as industry and agriculture. Although the presence of mycotoxins and phytoestrogens, such as lignans and coumestrans, in the aquatic environment is reported by some authors, their occurrence in Portuguese waters was not investigated yet. To evaluate the presence of phytoestrogens, phytosterols and mycotoxins in Douro River estuary, water samples were collected seasonally at nine sampling points, preconcentrated by solid phase extraction and analysed by gas chromatography mass spectrometry. Local flora was collected on the riverside, in the same sampling points, for identification and evaluation of the possible relation to the presence of phytoestrogens and/or phytosterols in the estuarine water. Results showed the ubiquitous presence of mycotoxins, namely deoxynivalenol up to 373.5 ng L(-1). Both phytoestrogens and phytosterols showed a possible seasonal fluctuation, which is in accordance to the life cycle of the local flora and agricultural practices. Physicochemical parameters were also determined for water quality evaluation. This study revealed for the first time the presence of mycotoxins and lignans in estuarine waters from Portugal, and highlights the need to consider natural contaminants in future monitoring programs.

Biomarker responses to estrogen and androgen exposure in the brook stickleback (Culaea inconstans): A new bioindicator species for endocrine disrupting compounds

Small-bodied freshwater fish are commonly used in regulatory testing for endocrine disrupting compounds (EDCs) but most lack a sensitive and quantifiable androgen-specific biomarker. Brook stickleback (Culaea inconstans) are a North American freshwater fish whose males produce an androgen-regulated glycoprotein in the kidney called spiggin. Although spiggin induction in females has been used as an androgen-specific biomarker of exposure in other stickleback species it has not been characterized in brook stickleback. Therefore, our objective was to develop a bioassay using brook stickleback to measure estrogenic and androgenic responses and establish the sensitivity of traditional and novel biomarkers of exposure. We first developed and optimized a qPCR assay to measure spiggin and vitellogenin transcript levels in kidney and liver tissue, respectively. Basal levels were differentially expressed in mature wild-caught male and female brook stickleback. To determine their sensitivity to EDCs, fish were exposed to nominal concentrations of 1, 10 and 100ng/L of 17α-methyltestosterone (MT) or 17α-ethinylestradiol (EE2) for 21days (sampled at 7 and 21days) under semi-static renewal conditions. MT and EE2 exposure induced spiggin and vitellogenin transcripts in female kidneys and male livers, respectively. Exposure to EE2 also increased hepatosomatic index in both sexes and decreased gonadosomatic index in females. Histopathological alterations were observed in the kidney of EE2-exposed fish and an increase in kidney epithelium cell height occurred in MT-exposed females. Given the sensitivity of these endpoints, the brook stickleback is a promising new freshwater fish model for EDC evaluation and a potential bioindicator for EDCs in North American freshwater environments.

Steroids in teleost fishes: A functional point of view

Steroid hormones are involved in the regulation of a variety of processes like embryonic development, sex differentiation, metabolism, immune responses, circadian rhythms, stress response, and reproduction in vertebrates. Teleost fishes and humans show a remarkable conservation in many developmental and physiological aspects, including the endocrine system in general and the steroid hormone related processes in particular. This review provides an overview of the current knowledge about steroid hormone biosynthesis and the steroid hormone receptors in teleost fishes and compares the findings to the human system. The impact of the duplicated genome in teleost fishes on steroid hormone biosynthesis and perception is addressed. Additionally, important processes in fish physiology regulated by steroid hormones, which are most dissimilar to humans, are described. We also give a short overview on the influence of anthropogenic endocrine disrupting compounds on steroid hormone signaling and the resulting adverse physiological effects for teleost fishes. By this approach, we show that the steroidogenesis, hormone receptors, and function of the steroid hormones are reasonably well understood when summarizing the available data of all teleost species analyzed to date. However, on the level of a single species or a certain fish-specific aspect of physiology, further research is needed.

Estrogen receptor 2b deficiency impairs the antiviral response of zebrafish

Although several studies have demonstrated the ability of some endocrine disruptive chemicals (EDCs) to alter the physiology of zebrafish, the immune-reproductive interaction has received little attention in this species. In this study, we used a homozygous line carrying an insertion of 8 amino acids in the ligand-binding domain of the estrogen receptor 2b gene (esr2b) to further understand the role of estrogen signaling on innate immunity. Adult mutant fish showed distorted sexual ratios related with alterations in testicular morphology and supraphysiological testosterone and 17β-estradiol (E2) levels. Immunity-wise, although esr2b mutant fish showed unaltered antibacterial responses, they were unable to mount an effective antiviral response upon viral challenge. RT-qPCR analysis demonstrated that mutant fish were able to induce the genes encoding major antiviral molecules, including Ifnphi1, Ifnphi2, Infphi3, Mxb and Mxc, and the negative feedback regulator of cytokine signaling Socs1. Notably, although esr2b mutant larvae showed a similar resistance to SVCV infection to their wild type siblings, waterborne E2 increased their viral susceptibility. Similarly, the exposure of adult wild type zebrafish to E2 also resulted in increased susceptibility to SVCV infection. Finally, the administration of recombinant Ifnphi1 hardly reversed the higher viral susceptibility of esr2b mutant zebrafish, suggesting that elevated socs1 levels impair Ifn signaling. All together, these results uncover an important role for E2 and Esr signaling in the fine-tuning of sexual hormone balance and the antiviral response of vertebrates.

Zebrafish sex differentiation and gonad development after exposure to 17α-ethinylestradiol, fadrozole and their binary mixture: A stereological study

Current knowledge on zebrafish (Danio rerio) sex determination suggests that this trait has a polygenic genetic basis, although environmental factors, such as endocrine disrupting chemicals (EDC), may also be involved in modeling or disturbing the species sex differentiation and development. This study aimed to assess how sex steroids imbalance triggers impact on sex differentiation and gonad development in zebrafish. Fish where exposed to an estrogen (EE2, i.e. 17α-ethinylestradiol, 4ng/L), to an inhibitor of estrogen synthesis (Fad, i.e. fadrozole, 50μg/L) or to their binary mixture (Mix-EE2+ Fad, 4ng/L+50μg/L), from 2h to 60 days post-fertilization (dpf). Afterwards, a quantitative (stereological) analysis using light microscopy, based on systematic sampling, was made at 35 and 60dpf, to identify alterations on gonad differentiation and development. During the sex differentiation period, our histological data showed that not all zebrafish males develop a "juvenile ovary", contrarily to what is currently taken for granted. Furthermore, the stereological analysis suggests that EE2 alone enhanced both zebrafish growth and gonad development. On the other hand, exposure to Fad affected the sexual development in zebrafish, inducing masculinization of the specimens, with some degree of intersex observed in males. In addition, the binary mixture allowed identifying sex-dependent roles of steroid hormones in the general growth and gonad development of zebrafish, with estrogens acting as growth promoters in females and being essential for ovary development. Data further support that sex-specific and single EDC impact studies are important, but clearly not sufficient to understand what may occur in the environment.

Inhibition of spawning in zebrafish (Danio rerio): Adverse outcome pathways of quinacrine and ethinylestradiol

This study determined the effects of the estrogen receptor agonist ethinylestradiol (EE2) and the phospholipase A2 inhibitor quinacrine (QUIN) on the pathways controlling follicular development, steroidogenesis, oocyte maturation, ovulation and spawning success in adult zebrafish. Both EE2 and QUIN inhibited spawning but did so through different mechanisms. EE2 affected follicular development (reduced ovarian size and reduction in the proportion of cortical alveolus, vitellogenic and mature follicle stages), steroidogenesis (reduced expression of aromatase), maturation (reduced luteinizing hormone receptor expression) and ovulation (reduced expression of cytosolic phospholipase A2 and the nuclear progesterone receptor). Although EE2 alters the proportion of follicle stages within the ovary, the downregulation of gene expression as a consequence of EE2 exposure was primarily due to a decline in expression of the genes of interest in vitellogenic and mature ovarian follicles. QUIN targeted ovulation via a reduction of the steroid 17α,20β dihydroxy-4-prenen-3-one (17α,20β-P) and decreased expression of the prostaglandin metabolizing enzyme cyclooxygenase 2. This study demonstrates the usefulness in defining the impacts of toxicants at the molecular and cellular, organ and whole organism level and how connections between these impacts can be used to describe the adverse outcome pathways (AOPs) that mediate toxicant action. Histological analysis and gene expression were effective tools in defining the AOPs of QUIN and EE2 while the measurement of reproductive hormones level did not provide much valuable information regarding the toxicant's mode of action.

Toxicological relevance of endocrine disruptors in the Tagus River estuary (Lisbon, Portugal)

The Tagus is the longest Iberian river, notwithstanding, the levels of natural and xenoestrogenic endocrine-disrupting compounds (EDCs) were never measured in its estuary. Suspecting for their presence, we made a major survey of 17 EDCs that include: (i) natural (17β-oestradiol and estrone) and pharmaceutical oestrogens (17α-ethynylestradiol); (ii) industrial and household pollutants (octylphenols, nonylphenols and their mono and diethoxylates, and bisphenol A); (iii) phytoestrogens (biochanin A, daidzein, formononetin, genistein); and (iv) the phytosterol (sitosterol). Water samples from the Tagus estuary were taken from nine locations every 2 months over a 1-year period and analysed by gas chromatography. Oestrogens, industrial/household pollutants were consistently higher at two sites-at Tagus River mouth and close to the Trancão tributary, both at Lisbon region. The overall oestrogenic load, in ethynylestradiol equivalents, was 13 ng/L for oestrogens, 2.3 ng/L for industrial/household pollutants and 43 ng/L for phytoestrogens; well in the range of toxicological significance. Water physicochemical parameters also indicated anthropogenic pollution, mainly at the two above-referred sampling sites.

Long-term effects of bisphenol AF (BPAF) on hormonal balance and genes of hypothalamus-pituitary-gonad axis and liver of zebrafish (Danio rerio), and the impact on offspring

Bisphenol AF (BPAF) is one of the analogues of bisphenol A (BPA) and is widely used as a raw material in the plastics industry. The potential toxicity to fish from exposure to BPAF in the aquatic environment is largely unknown. In this study, zebrafish (Danio rerio) were exposed to BPAF at 5, 25 and 125 μg L(-1), from 4 hour-post-fertilization (hpf) to 120 day-post-fertilization (dpf), representing the period from embryo to adult. The levels of plasma hormones were measured and the expression of selected representative genes along the hypothalamus-pituitary-gonad (HPG) axis and liver were examined. The concentration of 17β-estradiol (E2) was significantly increased in male and female fish and a significant decrease of testosterone (T) was observed in male fish. The mRNA expression of genes along the HPG axis and in liver tissues in F0 generation fish demonstrated that the steroid hormonal balances of zebrafish were modulated through the alteration of steroidgenesis. The significant decrease of egg fertilization among offspring indicates the possibility of sperm deterioration of parent following exposure to BPAF. The higher occurrence of malformation and lower survival rate in the offspring from the exposure group suggested a possibility of maternal transfer of BPAF, which could be responsible for the increased prevalence of adverse health signs in the offspring. The hatching delay in 5 μg L(-1) BPAF indicated that parental exposure to environmentally relevant concentration of BPAF would result in delayed hatching of the offspring. A potential consequence of adverse effects in the offspring by BPAF deserves further investigation.

Annual fluctuations of endocrine-disrupting compounds at the lower end of the Lima River, Portugal, and in adjacent coastal waters

The Lima River is a Spanish–Portuguese water body. Notwithstanding the fact that the river incorporates protected natural areas, levels of endocrine-disrupting compounds (EDCs) within its waters have never been measured; such EDCs include the following: natural and pharmaceutical oestrogens (17β-estradiol, E1, and 17α-ethynylestradiol), industrial and household pollutants (4-octylphenol, 4-nonylphenol, and their monoethoxylates and diethoxylates, and bisphenol A), phytoestrogens (formononetin, biochanin A, daidzein, genistein), and phytosterols (namely, sitosterol). To obtain an understanding of levels of EDCs, water samples were taken from eight sampling sites along the river every 2 months during a 1-year period (2011). The water samples were preconcentrated (Oasis HLB cartridges), cleaned (silica cartridges), and analysed using gas chromatography. Results showed that levels of oestrogens and industrial and household pollutants were higher in summer than in other seasons. Although oestrogens were more abundant (approximately 40 ng/L) on the southern margin of the river, levels of other pollutants were higher (approximately 124 ng/L) in the north. Phytoestrogens and sitosterol showed clear seasonal fluctuations with higher amounts of formononetin (approximately 389 ng/L), biochanin A (approximately 160 ng/L), and sitosterol (≥5 µg/L) measured in summer. The overall oestrogenic load, expressed in ethynylestradiol equivalents, was 18 ng/L for oestrogens, 0.5 ng/L for industrial and household pollutants, and 13 ng/L for phytoestrogens. Water physicochemical parameters indicate anthropogenic pollution because Σnitrites,nitrates (>1 mg/L) and phosphates (approximately 0.4 mg/L) were high. The study showed that the waters of the Lima River are subject to impacts and that levels of EDCs pose risks to the river’s biota.

Gonadal development and transcript profiling of steroidogenic enzymes in response to 17α-methyltestosterone in the rare minnow Gobiocypris rarus

It is well known that natural and anthropogenic chemicals interfere with the hormonal system of vertebrate and invertebrate organisms. How these chemicals regulate gonadal steroidogenesis remains to be determined. The main objective of this study was to evaluate the effects of 17α-methyltestosterone (MT), a synthetic model androgen, on gene expression profiles of six key steroidogenic genes in adult rare minnow. The full-length cDNA encoding 11β-hydroxysteroid dehydrogenase-2 (11β-HSD2) was firstly isolated and characterized by RT-PCR and RACE methods. The gonadal transcript changes of StAR, cyp11a1, 3β-HSD, cyp17a1, 11β-HSD2 and cyp19a1a in 6-month adult Gobiocypris rarus exposed to MT and 17α-ethinylestradiol (EE2) for 7, 14 and 21 days were detected by qRT-PCR. To make an effort to connect the transcriptional changes of steroidogenic enzymes with effects on higher levels of biological organization and on VTG, one remarkable sensitive target of steroids, body and gonad weights, histology of gonads, and hepatic vtg mRNA level were measured. MT caused varying degree of abnormalities in ovaries and testes. The hepatic vtg mRNA level was highly inhibited in females and slightly altered in males by MT. Transcripts of several steroidogenic genes including StAR, cyp17a1, and cyp11a1 showed high responsiveness to MT exposure in G. rarus. The gene expression profiles of these steroidogenic genes in MT-treated groups were much distinct with the EE2-treated group.

Short-term treatment of adult male zebrafish (Danio Rerio) with 17α-ethinyl estradiol affects the transcription of genes involved in development and male sex differentiation

The synthetic estrogen 17α-ethinyl estradiol (EE2) disturbs reproduction and causes gonadal malformation in fish. Effects on the transcription of genes involved in gonad development and function that could serve as sensitive biomarkers of reproductive effects in the field is, however, not well known. We have studied mRNA expression in testes and liver of adult zebrafish (Danio rerio) males treated with 0, 5 or 25 ng/L EE2for 14 days. qPCR analysis showed that the mRNA expression of four genes linked to zebrafish male sex determination and differentiation, Anti-Mullerian Hormone, Double sex and mab-related protein, Sry-related HMG box-9a and Nuclear receptor subfamily 5 group number 1b were significantly decreased by 25 ng/L, but not 5 ng/L EE2 compared with the levels in untreated fish. The decreased transcription was correlated with a previously shown spawning failure in these males (Reyhanian et al., 2011. Aquat Toxicol 105, 41-48), suggesting that decreased mRNA expression of genes regulating male sexual function could be involved in the functional sterility. The mRNA level of Cytochrome P-45019a, involved in female reproductive development, was unaffected by hormone treatment. The transcription of the female-specific Vitellogenin was significantly induced in testes. While testicular Androgen Receptor and the Estrogen Receptor-alpha mRNA levels were unchanged, Estrogen receptor-beta was significantly decreased by 25 ng/L EE2. Hepatic Estrogen Receptor-alpha mRNA was significantly increased by both exposure concentrations, while Estrogen Receptor-beta transcription was unaltered. The decreased transcription of male-predominant genes supports a demasculinization of testes by EE2 and might reflect reproductive disturbances in the environment.

Spatial and seasonal distribution of 17 endocrine disruptor compounds in an urban estuary (Mondego River, Portugal): evaluation of the estrogenic load of the area

The Mondego River estuary demonstrates signs of pollution, but the levels of endocrine disrupting compounds (EDCs), such as the natural (17β-estradiol and estrone) and pharmaceutical (17α-ethynylestradiol) estrogens, xenoestrogenic industrial pollutants (4-octylphenol, 4-nonylphenol, and their mono- and diethoxylates and bisphenol A), phytoestrogens (formononetin, biochanin A, daidzein, and genistein), and sitosterol were either poorly or never measured in this area. Thus, to conclude about the influx of EDCs in this estuary, water samples were taken every 2 months, during 1 year (2010) in low tide, at eight sites distributed along the estuary. Water samples (1 L) were preconcentrated in the Oasis HLB cartridges and cleaned in silica cartridges before their analysis by GC-MS. In summer, potentially hazardous amounts of estrogens (≈ 26 ng L(-1)), alkylphenols (≈ 11.5 μg L(-1)), alkylphenolethoxylates (≈ 13 μg L(-1)), and phytoestrogens (≈ 5.6 μg L(-1)) were measured. These data suggest that changes in the hydrodynamics of the estuary coupled with the increase of water temperatures interfere with the amount of EDCs in the water. Complementary physicochemical parameters also point to high levels of anthropogenic pollution in this area. Globally, the estrogenic load, expressed in ethynylestradiol equivalents, attained 71.8 ng L(-1) demonstrating that, all together, the measured EDCs pose important health risks for both biota and humans.