Effects of 3,3’,4,4’,5-pentachlorobiphenyl on in vitro oocyte maturation in dusky tripletooth goby, Tridentiger obscurus: an implication of estrogenic potency

1 Introduction

Considerable investigations have been carried out on various chemicals that can disrupt the endocrine system of humans and other animals (Colborn et al., 1993). These endocrine-disrupting chemicals (EDCs) include diverse chemicals such as pesticides, industrial detergents, sewage effluents, and polychlorinated biphenyls (PCBs). Several types of EDCs have the potential to mimic the estrogens of vertebrates, including fish (Scholz and Mayer, 2008; Diamanti-Kandarakis et al., 2009). Estrogens regulate physiological processes during vertebrate reproduction. In fish, vitellogenin production from the liver controlled by estradiol-17β (E₂), has been a powerful method for detecting the estrogenicity of EDCs (Jobling and Tyler, 2003; Navas and Segner, 2006). After vitellogenesis, progestins such as 17α,20β-dihydroxy-4-pregnen-3-one (17α20βP) and 17α,20β,21-trihydroxy-4-pregnen-3-one, induce final oocyte maturation, including germinal vesicle breakdown (GVBD) and ovulation (Nagahama et al., 1994; Das and Thomas, 1999). E₂ and estrogenic EDCs inhibit in vitro progesterone–induced GVBD in amphibian ovarian follicles Baulieu et al., 1978; Lin and Schuetz, 1983; Pickford and Morris, 1999). In addition, inhibition of progestin-induced GVBD by EDCs has been reported in fish oocytes (Ghosh and Thomas, 1995; Tokumoto et al., 2005; Hwang et al., 2010).

PCBs, including 209 congeners, have been used extensively in the industry as insulating materials, flame retardants, diluents, and detergents (Safe, 1994). PCBs have been reported to be environmental pollutants because of their high stability and bioaccumulation with lipophilic characteristics (Bonefeld-Jørgensen et al., 2001; Guruge et al., 2001). Among the various PCBs, 3,3’,4,4’,5-pentachlorobiphenyl (PCB126) is a coplanar congener and is known to be the most toxic PCB congener with dioxin-like properties (Safe, 1994). PCB126 is also an estrogen antagonist in mammals and fish (Lind et al., 1999; Wojtowicz et al., 2000; Muto et al., 2002; Vaccaro et al., 2005). In contrast, PCB 126 has been suggested to elicit estrogenic activity in fish (Gregoraszczuk et al., 2003a; Liu et al., 2006; Matthews et al., 2007; Mortensen and Arukwe, 2008a; Mortensen and Arukwe, 2008b). We reported that PCB126 does not have estrogenic or anti-estrogenic effects on in vitro steroid production from oocytes of the red lip mullet, Chelon haematocheilus (Baek et al., 2011). Gregoraszczuk et al., (2003b) reported that PCB126 has both estrogenic and anti-estrogenic effects in fish, depending on the time of exposure and developmental stage of follicles.

Despite the above contradictory studies, there are few studies with endocrine disrupting profiling of PCB126 on the maturation process of fish oocytes. Therefore, in the present study, we aimed to investigate the estrogenic potency of PCB126 on in vitro steroidogenesis in vitellogenic ovarian follicles of the dusky tripletooth goby, Tridentiger obscurus. Furthermore, we compared the estrogenic potency of PCB126 with that of exogenous E₂ treatment. We conducted a GVBD assay, liquid chromatography, and steroid hormone quantification to confirm the direct estrogenic potency of PCB126. Gobiid fish are appropriate subjects for investigating the effects of EDCs due to their small size, ease of handling, and strong tolerance even in the extreme environmental condition (Robinson et al., 2007). Therefore, we used the dusky tripletooth goby Tridentiger obscurus, an ideal model organism (Kaneko and Hanyu, 1985; Hwang et al., 2010), in the present study.

2 Materials and methods

2.1 Chemicals

Authentic steroids were purchased from Sigma Chemical (St. Louis, Missouri, USA) or Steraloids, Inc. (Wilton, NH, USA). Stock solutions (mg/mL) were prepared by dissolving the authentic steroids in pure ethanol. PCB126 (Aldrich Chemical, Milwaukee, WI, USA) was prepared as a stock solution (mg/mL) by diluting in ethanol. The ethanol concentration in the incubation medium was maintained at less than 0.1%. Testosterone (T) and E₂ were purchased from Sigma Chemical (St. Louis, MO, USA) or Steraloids, Inc. (Wilton, NH, USA). The antiserum for T was purchased from Sigma Chemical, and that for E₂ was kindly donated by Dr. Alexis Fostier (INRAE, Paris, France). Radioactive [³H]-17α-hydroxyprogesterone ([³H]-17αP), [³H]-T, and [³H]-E₂ were obtained from Amersham Life Sciences (London, England).

2.2 Experimental fish and histological observation of ovarian follicles

The dusky tripletooth goby used in this study were captured in coastal waters off Jeju Island, South Korea, during the spawning season (May–June). We isolated ovaries from 10 fishes. The ovaries were dissected manually into individual ovarian follicles using fine forceps. The ovarian follicles were separated in accordance with oocyte diameter of 0.53 and 0.78 mm from three different fish, respectively. And then we used these ovarian follicles for separated incubation experiment with duplicate (steroid metabolites analysis) or triplicate (RIA and GVBD assay). To determine the developmental stage of ovarian follicles, we conducted histological analysis. Gonadal fragments were processed by Midway and Scharf (2012). The paraffin-embedded samples were cut at 5-6 μm and sections were stained using Mayer’s hematoxylin and eosin and observed under a light microscope (BX50, Olympus, Japan).

2.3 Cell culture

Three separate experiments were performed. Prior to culture, ovarian follicles were separated in an ice-cold balanced salt solution (132.96 mM NaCl, 3.09 mM KCl, 0.28 mM MgSO₄·7H₂O, 0.98 mM MgCl₂·6H₂O, 3.40 mM CaCl₂·6H₂O, and 3.65 mM HEPES). Twenty ovarian follicles were incubated in 24-well culture plates containing 1 ml of Leibovitz L15 medium (Gibco, Grand Island, NY, USA).

To assess estrogenic potency of PCB126 on steroidogenic metabolism of ovarian follicles, we quantified steroid metabolites following exposure to PCB126 and exogenous E₂ in the presence of precursor. We incubated vitellogenic ovarian follicles with 10 and 100 ng/mL PCB126 or E₂ in the presence of [³H]-17αP (55 kBq) as a precursor in two separate experiments. To evaluate estrogenic potency of PCB126 on steroid production from vitellogenic ovarian follicles, we quantified T and E₂ levels following exposure to PCB126 and exogenous E₂. The vitellogenic ovarian follicles were incubated with only 1, 10 and 100 ng/mL of PCB126 or 0.01, 0.1 and 1 ng/mL E₂ in three separate experiments. For evaluation of estrogenic potency of PCB126 on final maturation process, we conducted GVBD assay. The fully vitellogenic ovarian follicles were separated and incubated with 0.1, 1, 10 and 100 ng/mL of PCB126 or E₂ in three separate experiments.

The plates were then incubated for 24 h at 18°C with gentle shaking. The pH and osmolality of the medium were adjusted to the plasma values of this species, 7.62 and 290 mOsm/kg, respectively.

2.4 Steroid metabolites

At the end of incubation with the radiolabeled precursor, the incubation media, and ovarian follicles were collected and stored at -80°C. Steroids were extracted three times from the medium and ovarian follicles, using 4 mL of dichloromethane. The extracts were concentrated and applied to a thin-layer chromatography (TLC) plate (60F²⁵⁴; Merck, Darmstadt, Germany) with non-radioactive standard steroids as carrier steroids and then developed in a mixture of benzene:acetone (4:1) and benzene:ethyl acetate (4:1). Radioactive steroid metabolites were analyzed using a BAS 1500 bio-imaging analyzer (Fuji Film, Tokyo, Japan), and standards E₁ and E₂ were visualized by exposure to iodine vapor. Other standard steroids were detected using UV absorption at 254 nm. The migration zones corresponding to the carrier steroids, T and E_2, were eluted twice from the bands of the silica plates with 5 ml of dichloromethane:methanol (90:10). Following centrifugation at 1000 × g for 10 min, the supernatants were vacuum-dried before being dissolved in 20 μl of acetonitrile. The extracts were then analyzed using reverse-phase high-performance liquid chromatography (HPLC; Table 1). After HPLC analysis, metabolites with the same retention time as the standard were recovered and identified using gas chromatography-mass spectrometry (GC-MS, Table 2).

TABLE 1

Table 1 HPLC instruments and analysis conditions for separation of steroid metabolites.

TABLE 2

Table 2 Analytical conditions of gas chromatography-mass spectrometry for identification of steroid metabolites.

2.5 Radioimmunoassay

After incubation, steroids were extracted twice from aliquots of the medium, using ethyl acetate and cyclohexane. Then, T and E₂ levels were measured by radioimmunoassay (RIA), following Kobayashi et al., 1987. The intra-assay coefficients of variance were 2.5% (n=3) and 3.2% (n=3) for the T and E₂ assays, respectively, and the respective inter-assay coefficients of variance were 12.1% (n=5) and 11.3% (n=5). The minimum detectable limits were 10.5 and 12.2 pg/mL for T and E_2, respectively.

2.6 GVBD assay

For the GVBD assay, the incubated ovarian follicles were fixed with a clearing solution (ethanol:formalin:glacial acetic acid, 6:3:1) after 24 h of incubation. The location of the germinal vesicle (GV = nucleus) was observed under low-power magnification using a dissection microscope. The number of ovarian follicles completing GVBD, that is, the dissolution of the nucleus, was counted in each well and calculated as a percentage.

2.7 Statistics

The data from RIA and GVBD were expressed as mean with a standard error of the mean (SEM) from three separate experiments (n =3). These data were analyzed by Kolmogorov-Smirnov and Levene’s test to verify whether the variance fulfilled the conditions of normality and homogeneity, respectively. The results were not satisfactory fit to the normal distribution and were therefore conducted in the non-parametric test. Differences between control and each treatment were analyzed by Kruskal-Wallis test followed by Bonferroni adjustment. Statistical significance was set at p < 0.05 using SPSS 11.0 for Windows (SPSS, Inc., Chicago, IL, USA).

3 Results

3.1 Histological observations of the ovarian follicles

In 0.53-mm-diameter ovarian follicles, yolk globules (Yg) were accumulated into the cytoplasm, the oil droplets (Ods) were distributed over the cytoplasm, and the nucleus was present in the center of oocytes (Figure 1A). In 0.78-mm-diameter oocytes, Yg and Ods continued to accumulate to the cytoplasm (Figure 1B). In these oocytes, one or two large Ods (40–50 μm) were observed around the nucleus, and the nucleus began to migrate.

FIGURE 1

Figure 1 Histological observations of oocytes from dusky tripletooth goby. (A) oocytes of 0.53 mm; (B) oocytes of 0.76 mm. Scale bars indicate 200 μm. N, nucleus; Od, oil droplet; Yg, yolk granule.

3.2 Effects of PCB126 and E₂ on steroid metabolites from [³H]-17αP

When vitellogenic ovarian follicles (0.53 mm in diameter) were incubated with [³H]-17αP, the two major metabolites were separated and identified as T and E₂ by TLC, HPLC, and GC/MS (Figures 2, 3). Fractions of two progestins, co-migrated with standard 17α20βP and 17α,20α-dihydroxy-4-pregnen-3-one (17α20αP), were not identified because of their low levels. Steroid metabolites produced from [³H]-17αP in the presence of PCB126 and E₂ were compared with the values obtained from photo-stimulated luminescence (PSL) autoradiography (Figure 4).

FIGURE 2

Figure 2 Autoradiograms of steroid metabolites incubated with [³H]-17αP from dusky tripletooth goby oocytes. T and E₂ were separated by thin layer chromatography developed with a benzene: acetone (4: 1) and benzene: ethyl acetate (4: 1) mixture. 1, Control; 2, E₂ 10 ng/mL; 3, E₂ 100 ng/mL; 4, PCB126 10 ng/mL; 5, PCB126 100 ng/mL.

FIGURE 3

Figure 3 Mass spectra of steroid metabolized from dusky tripletooth goby oocytes were identified as T and E₂. (A) authentic T; (B) metabolized T; (C) authentic E₂; (D) metabolized E₂.

FIGURE 4

Figure 4 Comparison of radioactivity distribution on the TLC plate by digital photo-stimulated luminescence (PSL) autoradiography. The chromatograms are normalized to the maximum peak intensity in each chromatogram. 1, fraction of T metabolite; 2, fraction of E₂ metabolite.

In T metabolites (Table 3), both 10 and 100 ng/ml PCB126 stimulated T synthesis (11.05, 13.74 and 10.82, 15.95 (PSL-BG)/mm², respectively), compared with the control (10.44 and 11.80 (PSL-BG)/mm²). Exogenous E₂ treatment with 10 and 100 ng/ml also stimulated T synthesis (14.79, 15.52 and 12.50, 16.90 (PSL-BG)/mm², respectively) compared with the control.

TABLE 3

Table 3 Effects of PCB126 and E₂ on metabolites of T from radioactive precursor.

In E₂ metabolites (Table 4), both 10 and 100 ng/ml PCB126 stimulated E₂ synthesis (23.31, 32.96 and 18.90, 31.95 (PSL-BG)/mm², respectively) compared with the control (18.76 and 25.89 (PSL-BG)/mm²). Exogenous E₂ treatment with 100 ng/ml also stimulated E₂ synthesis (23.55 and 34.73 (PSL-BG)/mm²); however, the second value in the treatment with 10 ng/ml (25.44 (PSL-BG)/mm²) was decreased slightly compared to controls.

TABLE 4

Table 4 Effects of PCB126 and E₂ on metabolites of E₂ from radioactive precursor.

3.3 Effects of PCB126 and E₂ on steroid production

PCB126 treatment with 100 ng/mL decreased T production (152.60 ± 16.49 pg/mL) compared to the control (212.93 ± 7.31 pg/mL, p < 0.05), although there were no significant effects at 1 and 10 ng/mL of PCB126 treatment (Figure 5). In the exogenous E₂ treatment, E₂ decreased T production in a dose-dependent manner; however, the effect was not significant. E₂ treatment (1 ng/mL) increased E₂ production (3353.85 ± 385.93 pg/mL) compared with the control. (1228.91 ± 136.15 pg/mL, p < 0.05). Lower concentrations of E₂ (0.01 and 0.1 ng/mL) increased E₂ production slightly, although there was no significant effect.

FIGURE 5

Figure 5 Effects of PCB126 on in vitro steroid production in dusky tripletooth goby oocytes (oocyte diameter=0.53 mm) after a 24 h incubation. Values are the mean ± SE of each steroid in three replicate wells with 20 oocytes/well. Data were analyzed using the Kruskal–Wallis test followed by the Bonferroni adjustment. Asterisks show significant differences from controls (p < 0.05).

In the ratio of E₂/T, as a sensitive biomarker of sex-steroid concentrations (Bevans et al., 1996; Folmar et al., 1996), PCB126 increased E₂/T significantly at the highest dose (12.07 ± 1.28) compared to the control (5.22 ± 0.68, p < 0.05). Exogenous E₂ treatment also increased E₂/T significantly at the highest dose (18.27 ± 3.44) compared to the control (4.52 ± 0.80, p < 0.05).

3.4 Effects of PCB126 and E₂ on GVBD

We incubated germinal vesicle migratory (GVM) ovarian follicles (0.78 mm diameter) with PCB126 or exogenous E₂. PCB126 decreased GVBD in all treatments, and 10 and 100 ng/mL PCB126 resulted in a significant decrease in GVBD (0.94 ± 0.77 and 0%) compared with the control (12.12 ± 1.52%, p < 0.05). In the exogenous E₂ treatment, 0.1, 10, and 100 ng/mL E₂ resulted in a decrease in GVBD, although there were no significant differences (Figure 6).

FIGURE 6

Figure 6 Effects of different PCB126 concentrations on in vitro GVBD in dusky tripletooth goby oocytes (oocyte diameter = 0.78 mm) after a 24 h incubation. Values are means ± SEM of the percentage of GVBD in three replicate wells with 20 oocytes/well. Controls were incubated with only incubation medium. Data were analyzed using the Kruskal-Wallis test followed by Bonferroni adjustment. Asterisks show significant differences from controls (P < 0.05).

4 Discussion

In the present study, we investigated the estrogenic potency of PCB126 on in vitro steroid synthesis in vitellogenic ovarian follicles with an exogenously labeled precursor. In addition, we compared estrogenic potency in the final oocyte maturation process with that in GVM ovarian follicles. There have been controversies regarding PCB126 whether its effects are estrogenic or anti-estrogenic, although it is the most toxic PCB congener (Safe, 1994; Lind et al., 1999; Wojtowicz et al., 2000; Gregoraszczuk et al., 2003a, b; Vaccaro et al., 2005; Mortensen and Arukwe, 2008a, b; Gregoraszczuk et al., 2008; Sechman et al., 2016). The different effects may be caused by the diverse actions of the aryl hydrocarbon receptor (AhR) (Calo et al., 2010). In our previous study, PCB126 had no significant effect on in vitro E₂ production from the ovarian follicles of red lip mullet (Baek et al., 2011). Coupled with prior studies, Gjernes et al. (2012) hypothesized that PCB126 has estrogenicity via estrogen receptor (ER)-hijacking (modulating estrogenic responses with activated AhR in the absence of an ER agonist). Recent studies have also reported that PCB126 exhibits estrogenic activity (Pinto et al., 2018; Licata et al., 2019).

In the present study, we separated and identified two major metabolites, T and E2. The metabolites were scanned and the data were converted as a PSL value. According to Kamarainen et al. (2006), PSL provides high sensitivity and resolution and superior linearity compared with the other methods such as radioactivity scanning and film autoradiography. Our results indicate that PCB126 has estrogenic potency in 0.53 mm diameter ovarian follicles; it stimulated not only E₂ metabolites but also E₂ production, in vitro. Since aromatase is the key enzyme for converting androgen to estrogen (Nagahama et al., 1994), we considered that PCB126 may stimulate aromatase activity, resulting in a decrease in T production and an increase in E₂ production from RIA results. These were remarkably analogous to the exogenous E₂ treatment. However, PCB126 and exogenous E₂ stimulated T metabolite biosynthesis in the presence of the labeled precursor. This difference may be due to different steroidogenic pathways and/or activities due to the absence or presence of the exogenous precursor, [³H]-17αP.

Coupled with the results of the increase in E₂ metabolites, however, we could not identify two progestins that co-migrated with 17α20αP and 17α20βP in our LC system due to their low activity (data not shown). To date, maturation inducing steroid (MIS) of the dusky tripletooth goby has not yet been identified, although 17α20βP, the representative progestin, has been reported as a MIS in various teleost species (Nagahama and Yamashita, 2008). Previous studies have reported that 17α20αP may act as an MIS in several fish species (Canario and Scott, 1990; Hwang and Baek, 2021). The identification of these progestins, their maturational capacity, and the effects of PCB126 on progestin synthesis would provide more information about the estrogenic potency of PCB126.

PCB126 may act as an estrogen or anti-estrogen depending on the time and dose of exposure and different physiological conditions, even in different stages of ovarian development (Wojtowicz et al., 2000; Gregoraszczuk et al., 2003a; b; Mortensen and Arukwe, 2008b). Therefore, we studied the estrogenic potency of PCB126 in the final oocyte maturation process in GVM ovarian follicles and hypothesized that PCB126 may also indicate estrogenic potency analogous to exogenous E₂ at this stage. Our results clearly indicate that PCB126 inhibits GVBD, similar to exogenous E₂ treatment. The inhibitory effect of high doses of PCB126 on GVBD was stronger than that of the exogenous E₂ treatment. However, we could not quantify steroid levels from the incubation media of 0.78-mm ovarian follicles due to problems with collecting media. We suspect that PCB126 may disrupt the activity of steroidogenic enzymes, increase E₂ levels and decrease progestogen levels such as 17α20βP, simultaneously. Prior to the maturation stage, there is a dramatic shift in the steroidogenic pattern; an increase in the formation of progestins concurrently with a decline in E₂ level (Nagahama et al., 1994). The shift in the steroidogenic pattern from the synthesis of estrogens and androgens toward the synthesis of progestins involves a decrease in 17-20 lyase activity and a rise in that of 20β-hydroxysteroid dehydrogenase (HSD). An inhibitory mechanism of PCBs on mammalian oocyte maturation was reported; PCBs acted as toxicants and thus inhibited maturation (Pocar et al., 2006). However, we need to consider the estrogenic potency of PCB126: it stimulates E₂ production directly so that inhibition of GVBD by its estrogenic effect rather than toxicity.

The estrogenic effect or estrogenicity defined by previous study (Scholz and Mayer, 2008) refers to (1) mimicking the action of estrogens and activation of responsive genes, or (2) elevation of endogenous plasma estrogen levels caused by competitive binding of EDCs to sex steroid-binding globulins. Although we did not conduct these experiments, our results suggest that PCB126 has an estrogenic potency, stimulates the biosynthesis of E₂ from vitellogenic ovarian follicles, and inhibits GVBD from GVM ovarian follicles with effects analogous to exogenous E₂.

5 Conclusion

In fish, the function of estrogens associated with reproductive characteristics (single or multiple spawning, vitellogenic or maturation stage, and so on) varies, and may regulate many other physiological processes (Nelson and Habibi, 2013). Up to date, PCB126, the most toxic PCB congener may act as an estrogenic agonist or antagonist in various species. The present study demonstrated that PCB126 has an estrogenic potency; (1) increase in E₂ synthesis and (2) decrease in GVBD in vitro during the oocyte maturation process of T. obscurus. Future studies with authentic steroidogenic pathway, changes in progestin levels and the related steroidogenic enzymes during this period would be conducted for more comprehension in estrogenic mechanism of PCB126.

Data availability statement

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

Ethics statement

The animal study was reviewed and approved by Animal Ethics Committee of Pukyong National University (PKNU; Regulation No. 554).

Author contributions

IH: conceptualization, methodology, formal analysis, investigation, writing – original draft, visualization. HB: conceptualization, writing – review & editing, visualization, supervision, project administration, funding acquisition. All authors contributed to the article and approved the submitted version.

Funding

This study was supported by the National Institute of Fisheries Science, Ministry of Oceans and Fisheries, Korea (R2023016).

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

References

Baek H. J., Hwang I. J., Lee Y. D., Kim H. B. (2011). Effects of nonylphenol and 3,3’4,4’5-pentachlorobiphenyl on in vitro oocyte steroidogenesis in redlip mullet, Chelon haematocheilus. Anim. Cells Syst. 15, 189–196. doi: 10.1080/19768354.2011.604938

CrossRef Full Text | Google Scholar

Baulieu E. E., Godeau F., Schorderet M., Schorderet-Slatkine S. (1978). Steroid-induced meiotic division in Xenopus laevis oocytes: surface and calcium. Nature 275, 593–598. doi: 10.1038/275593a0

PubMed Abstract | CrossRef Full Text | Google Scholar

Bevans H. E., Goodbred S. L., Miesner J. F., Watkins S. A., Gross T. S., Denslow N. D., et al. (1996). Synthetic organic compounds and carp endocrinology and histology in Las Vegas Wash and Las Vegas and Callville Bays of Lake Mead, Nevada 1992 and 1995. In Water Resources Investigations Report 96-4266. Carson City, NV, USA: US Department of the Interior-US Geological Survey, Vol. 12.

Google Scholar

Bonefeld-Jørgensen E. C., Andersen H. R., Rasmussen T. H., Vinggaard A. M. (2001). Effect of highly bioaccumulated polychlorinated biphenyl congeners on estrogen and androgen receptor activity. Toxicology 158, 141–153. doi: 10.1016/S0300-483X(00)00368-1

PubMed Abstract | CrossRef Full Text | Google Scholar

Calo M., Alberghina D., Bitto A., Lauriano E. R., Cascio P. L. (2010). Estrogenic followed by anti-estrogenic effects of PCBs exposure in juvenile fish (Spaurus aurata). Food Chem.Toxicol. 48, 2458–2463. doi: 10.1016/j.fct.2010.06.013

PubMed Abstract | CrossRef Full Text | Google Scholar

Canario A. V. M., Scott A. P. (1990). Plasma levels of ovarian steroids, including 17α,20α- dihydroxy-4-pregnen-3-one and 3β,17α,20α-trihydroxy-5β-pregnane, in female dabs (Limanda limanda) - marine flatfish - induced to mature and ovulate with human chorionic gonadotrophin. Gen. Comp. Endocrinol. 77, 177–191. doi: 10.1016/0016-6480(90)90302-3

PubMed Abstract | CrossRef Full Text | Google Scholar

Colborn T., Vom Saal F. S., Soto A. M. (1993). Developmental effects of endocrine disrupting chemicals in wildlife and humans. Environ. Health Perspect. 101, 378–384. doi: 10.1289/ehp.93101378

PubMed Abstract | CrossRef Full Text | Google Scholar

Das S., Thomas P. (1999). Pesticides interfere with nongenomic action of a progestogen on meiotic maturation by binding to its plasma membrane receptor on fish oocytes. Endocrinology 140, 1953–1956. doi: 10.1210/endo.140.4.6781

PubMed Abstract | CrossRef Full Text | Google Scholar

Diamanti-Kandarakis E., Bourguignon J. P., Giudice L. C., Hauser R., Prins G. S., Soto A. M. R., et al. (2009). Endocrine-disrupting chemicals: an endocrine society scientific statement. Endocr. Rev. 30, 293–342. doi: 10.1210/er.2009-0002

PubMed Abstract | CrossRef Full Text | Google Scholar

Folmar L. C., Denslow N. D., Rao V., Chow M., Crain D. A., Enblom J., et al. (1996). Vitellogenin induction and reduced serum testosterone concentrations in feral male carp (Cyprinus carpio) captured near a major metropolitan sewage treatment plant. Environ. Health Perspect. 104, 1096–1101. doi: 10.1289/ehp.961041096

PubMed Abstract | CrossRef Full Text | Google Scholar

Ghosh S., Thomas P. (1995). Antagonistic effects of xenobiotics on steroid-induced final maturation of Atlantic croaker oocytes in vitro. Mar. Environ. Res. 39, 159–163. doi: 10.1016/0141-1136(94)00036-O

CrossRef Full Text | Google Scholar

Gjernes M. H., Schlenk D., Arukwe A. (2012). Estrogen receptor-hijacking by dioxin-like 3,3’4,4’,5-pentachlorobiphenyl (PCBC126) in salmon hepatocytes involves both receptor activation and receptor protein stability. Aquat. Toxicol. 124-125, 197–208. doi: 10.1016/j.aquatox.2012.08.015

PubMed Abstract | CrossRef Full Text | Google Scholar

Gregoraszczuk E. L., Grochowalski A., Chrzaszcz R., Wegiel M. (2003a). Congener-specific accumulation of polychlorinated biphenyls in ovarian follicular wall follows repeated exposure to PCB126 and PCB153. comparison of tissue levels of PCB and biological changes. Chemosphere 50, 481–488. doi: 10.1016/S0045-6535(02)00637-9

PubMed Abstract | CrossRef Full Text | Google Scholar

Gregoraszczuk E. L., Sowa M., Kajta M., Ptak A., Wójtowicz A. (2003b). Effect of PCB126 and PCB153 on incidence of apoptosis in cultured theca and granulosa cells collected from small, medium and large preovulatory follicles. Reprod. Toxicol. 17, 465–471. doi: 10.1016/S0890-6238(03)00042-x

PubMed Abstract | CrossRef Full Text | Google Scholar

Gregoraszczuk E. L., Rak A., Ludewig G., Gasin’ska A. (2008). Effects of estradiol, PCB3 and their hydroxylated metabolites on proliferation, cell cycle, and apoptosis of human breast cancer cells. Environ. Toxicol. Pharmacol. 25, 227–233. doi: 10.1016/j.etap.2007.10.004

PubMed Abstract | CrossRef Full Text | Google Scholar

Guruge K. S., Watanabe M., Tanaka H., Tanabe S. (2001). Accumulation status of persistent organochlorines in albatrosses from the north pacific and the southern ocean. Environ. Pollut. 114, 389–398. doi: 10.1016/S0269-7491(00)00234-7

PubMed Abstract | CrossRef Full Text | Google Scholar

Hwang I. J., Baek H. J. (2021). In vitro Sex steroid metabolism in red spotted grouper, Epinephelus akaara during oocyte maturation. Dev. Reprod. 25, 75–82. doi: 10.12717/DR.2021.25.2.75

PubMed Abstract | CrossRef Full Text | Google Scholar

Hwang I. J., Kim H. W., Kim J. K., Lee Y. D., Baek H. J. (2010). Estrogenicity of 4-nonylphenol and diethylstilbestrol on in vitro oocyte maturation of the dusky tripletooth goby, Tridentiger obscurus. Anim. Cells Syst. 14, 161–167. doi: 10.1080/19768354.2010.504339

CrossRef Full Text | Google Scholar

Jobling S., Tyler C. R. (2003). Endocrine disruption, parasites and pollutants in wild freshwater fish. Parasitology 126, S103–S108. doi: 10.1017/S0031182003003652

PubMed Abstract | CrossRef Full Text | Google Scholar

Kamarainen E., Haaparanta M., Siitari-Kauppi M., Koivula T., Lipponen T., Solin O. (2006). Analysis of 18F-labelled synthesis products on TLC plates: comparison of radioactivity scanning, film autoradiography, and a phosphoimaging technique. Appl. Radiat. Isot. 64, 1043–1047. doi: 10.1016/j.apradiso.2006.04.012

PubMed Abstract | CrossRef Full Text | Google Scholar

Kaneko T., Hanyu I. (1985). Annual reproductive cycle of the chichibu goby, Tridentiger obscurus. Bull. Jap. Soc Sci. Fish. 51, 1645–1650. doi: 10.2331/suisan.51.1645

CrossRef Full Text | Google Scholar

Kobayashi M., Aida K., Sakai H., Kaneko T., Asahina K., Hanyu I., et al. (1987). Radioimmunoassay for salmon gonadotropin. Nippon Suisan Gakk. 53, 995–1003. doi: 10.2331/suisan.53.995

CrossRef Full Text | Google Scholar

Licata P., Tardugno R., Pergolizzi S., Capillo G., Aragona M., Colombo A., et al. (2019). In vivo Effects of PCB-126 and genistein on vitellogenin expression in zebrafish. Nat. Prod. Res. 17, 2507–2514. doi: 10.1080/14786419.2018.1455048

CrossRef Full Text | Google Scholar

Lin Y. W. P., Schuetz A. W. (1983). In vitro Estrogen modulation of pituitary and progesterone-induced oocyte maturation in Rana pipiens. J. Exp. Zool. 97, 281–292. doi: 10.1002/jez.1402260214

CrossRef Full Text | Google Scholar

Lind P. M., Eriksen E. F., Sahlin L., Edlund M., Orberg J. (1999). Effects of the antiestrogenic environmental pollutant 3,3’,4,4’,5-pentachlorobiphenyl (PCB126) in rat bone and uterus: diverging effects in ovariectomized and intact animals. Toxicol. Appl. Pharmacol. 154, 236–244. doi: 10.1006/taap.1998.8568

PubMed Abstract | CrossRef Full Text | Google Scholar

Liu S., Abdelrahim M., Khan S., Ariazi E., Jordan V. C., Safe S. (2006). Aryl hydrocarbon receptor agonists directly activate estrogen receptor alpha in MCF-7 breast cancer cells. Biol. Chem. 387, 1209–1213. doi: 10.1515/BC.2006.149

PubMed Abstract | CrossRef Full Text | Google Scholar

Matthews J., Wihlen B., Heldring N., MacPherson L., Helguero L., Treuter E., et al. (2007). Coplanar 3,3’,4,4’,5-pentachlorinated biphenyl and non-coplanar 2,2’,4,6,6’-pentachlorinated biphenyl differentially induce recruitment of estrogen receptor alpha to aryl hydrocarbon receptor target genes. Biochem. J. 406, 343–353. doi: 10.1042/BJ20070585

PubMed Abstract | CrossRef Full Text | Google Scholar

Midway S. R., Scharf F. S. (2012). Histological analysis reveals larger size at maturity for southern flounder with implications for biological reference points. Mar. Coast. Fish. 4, 628–638. doi: 10.1080/19425120.2012.717524

CrossRef Full Text | Google Scholar

Mortensen A. S., Arukwe A. (2008a). Estrogenic effect of dioxin-like aryl hydrocarbon receptor (AhR) agonist (PCB congener 126) in salmon hepatocytes. Mar. Environ. Res. 66, 119–120. doi: 10.1016/j.marenvres.2008.02.041

PubMed Abstract | CrossRef Full Text | Google Scholar

Mortensen A. S., Arukwe A. (2008b). Activation of estrogen receptor signaling by the dioxin-like aryl hydrocarbon receptor agonist, 3,3’,4,4’,5-pentachlorobiphenyl (PCB126) in salmon in vitro system. Toxicol. Appl. Pharmacol. 227 (2), 313–324. doi: 10.1016/j.taap.2007.11.003

PubMed Abstract | CrossRef Full Text | Google Scholar

Muto T., Wakui S., Imano N., Nakaaki K., Takahashi H., Hano H., et al. (2002). Mammary gland differentiation in female rats after prenatal exposure to 3,3’,4,4’,5-pentachlorobiphenyl. Toxicology 177, 197–205. doi: 10.1016/S0300-483X(02)00224-X

PubMed Abstract | CrossRef Full Text | Google Scholar

Nagahama Y., Yamashita M. (2008). Regulation of oocyte maturation in fish. Dev. Growth Differ. 50, S195–S219. doi: 10.1111/j.1440-169X.2008.01019.x

PubMed Abstract | CrossRef Full Text | Google Scholar

Nagahama Y., Yoshikuni M., Yamashita M., Tanaka M. (1994). “Regulation of oocyte maturation in fish,” in Fish physiology. V13. molecular endocrinology of fish. Eds. Sherwood N. M., Hew C. L. (London: Academic Press), 393–439.

Google Scholar

Navas J. M., Segner H. (2006). Vitellogenin synthesis in primary cultures of fish liver cells as endpoint for in vitro screening of the (anti)estrogenic activity of chemical substances. Aquat. Toxicol. 80, 1–22. doi: 10.1016/j.aquatox.2006.07.013

PubMed Abstract | CrossRef Full Text | Google Scholar

Nelson E. R., Habibi H. R. (2013). Estrogen receptor function and regulation in fish and other vertebrates. Gen. Comp. Endocrinol. 192, 15–24. doi: 10.1016/j.ygcen.2013.03.032

PubMed Abstract | CrossRef Full Text | Google Scholar

Pickford D. B., Morris I. D. (1999). Effects of endocrine-disrupting contaminants on amphibian oogenesis: methoxychlor inhibits progesterone-induced maturation of Xenopus laevis oocytes in vitro. Environ. Health Perspect. 107, 285–292. doi: 10.1289/ehp.99107285

PubMed Abstract | CrossRef Full Text | Google Scholar

Pinto C. L., Markey K., Dix D., Browne P. (2018). Identification of candidate reference chemicals for in vitro steroidogenesis. toxicol. In Vitro 47, 103–119. doi: 10.1016/j.tiv.2017.11.003

CrossRef Full Text | Google Scholar

Pocar P., Brevini T. A. L., Antonini S., Gandolfi F. (2006). Cellular and molecular mechanisms mediating the effect of polychlorinated biphenyls on oocyte in vitro maturation. Reprod. Toxicol. 22, 242–249. doi: 10.1016/j.reprotox.2006.04.023

PubMed Abstract | CrossRef Full Text | Google Scholar

Robinson C. D., Brown E., John A. C., Davies I. M., Megginson C., Miller C., et al. (2007). Bioindicators and reproductive effects of prolonged 17β-oestradiol exposure in a marine fish, the sand goby (Pomatoschistus minutus). Aquat. Toxicol. 81, 397–408. doi: 10.1016/j.aquatox.2006.12.020

PubMed Abstract | CrossRef Full Text | Google Scholar

Safe S. (1994). Polychlorinated biphenyls (PCBs): environmental impact, biochemical and toxic responses, and implications for risk assessment. Crit. Rev. Toxicol. 24, 87–149. doi: 10.3109/10408449409049308

PubMed Abstract | CrossRef Full Text | Google Scholar

Scholz S., Mayer I. (2008). Molecular biomarkers of endocrine disruption in small model fish. Mol. Cell. Endocrinol. 293, 57–70. doi: 10.1016/j.mce.2008.06.008

PubMed Abstract | CrossRef Full Text | Google Scholar

Sechman A., Batoryna M., Antos P. A., Hrabia A. (2016). Effects of PCB 126 and PCB 153 on secretion of steroid hormones and mRNA expression of steroidogenic genes (STAR, HSD3B, CYP19A1) and estrogen receptors (ERα, ERβ) in prehierarchical chicken ovarian follicles. Toxicol. Lett. 264, 29–37. doi: 10.1016/j.toxlet.2016.11.001

PubMed Abstract | CrossRef Full Text | Google Scholar

Tokumoto T., Tokumoto M., Nagahama Y. (2005). Induction and inhibition of oocyte maturation by EDCs in zebrafish. Reprod. Biol. Endocrinol. 3, 69. doi: 10.1186/1477-7827-3-69

PubMed Abstract | CrossRef Full Text | Google Scholar

Vaccaro E., Meucci V., Intorre L., Soldani G., Di Bello D., Longo V., et al. (2005). Effects of 17β-estradiol, 4-nonylphenol and PCB126 on the estrogenic activity and phase 1 and 2 biotransformation enzymes in male sea bass (Dicentrarchus labrax). Aquat. Toxicol. 75, 293–305. doi: 10.1016/j.aquatox.2005.08.009

PubMed Abstract | CrossRef Full Text | Google Scholar

Wojtowicz A. K., Gregoraszczuk E. L., Lyche J. L., Ropstad E. (2000). Time dependent and cell-specific action of polychlorinated biphenyls (PCB153 and PCB126) on steroid secretion by porcine theca and granulosa cells in monoand co-culture. J. Physiol. Pharmacol. 51, 555–568.

PubMed Abstract | Google Scholar