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Polychlorinated biphenyls (PCBs) have been detected at high levels, up to hundreds of pg/ml, in human ovarian follicle fluid. The effect of PCBs on the ovary and the consequences of exposure are largely unknown. We have previously shown that PCB3 (4-chlorobiphenyl) increases the secretion of estradiol and the activity of cytochrome P450s (CYPs) in ovarian follicle cells. Our goal here is to elucidate the mechanism of CYP induction by this congener. Exposure of porcine follicle cells, a co-culture of theca and granulosa cells, to 6 ng/ml of PCB3 caused an increase in CYP1A1 protein and enzymatic activity, in the same manner as exposure to exogenous 17ß-estradiol. No changes were seen in the protein level of the aryl hydrocarbon receptor (AhR), which mediates the first step in the signaling pathway of CYP1A1 induction. However, a strong reduction was seen in the protein level of estrogen receptor beta (ERß), while no effect was seen on ER protein levels. These result suggest that: 1) PCB3 acts as an agonist of ERß but not the Ah receptor in the ovarian follicles, 2) PCB3 is not only an efficacious inducer of CYP1A1 expression and activity, but also a substrate for this enzyme. Changes in the expression level of CYP1A1 not only alter the intensity of the activity of PCB3, but also the activity of estrogen in the ovary.
The aims of the study were to compare the in vitro effects of daidzein or 17ß-estradiol (E2) on: 1) progesterone (P4) secretion by luteinized granulosa cells harvested from large porcine follicles, as well as 2) estrogen receptor and ß (ER and ERß) mRNA and protein expression in the cells. In addition, the effect of daidzein on E2 secretion and viability of the granulosa cells was examined. We found that basal and gonadotropin-stimulated P4 secretion were inhibited in granulosa cells cultured in the presence of daidzein either for 24 or 48 hours. In contrast to daidzein, E2 reduced P4 secretion only during 24-hour cell cultures increasing it during longer cultures. Daidzein did not affect E2 secretion by granulosa cells. The expression of ER and ERß mRNA, as well as ERß protein, was up-regulated by daidzein but unaffected by E2. To conclude, the soy estrogen daidzein acts directly on the porcine ovary to decrease progesterone production and to increase expression of ERß mRNA and protein. Daidzein actions in porcine luteinized granulosa cells differ from those of estradiol and it may suggest disadvantageous effects of the phytoestrogen on reproductive processes in females.
Background. In teleost fishes, the brain is the target organ for sex steroid hormones. The actions of sex steroid hormones are mediated by their receptors and play an important role in the regulation of endocrine function in the brain. Japanese medaka, Oryzias latipes, is a species widely used in many fields of experimental biology, including neurobiology. In this study, we examined the mRNA expression levels of androgen and estrogen receptors in medaka brains. Materials and Methods. The brains of adult fish were separated into three parts (forebrain, midbrain and hindbrain). The expression levels of androgen receptor (AR) and estrogen receptor (ER) β from each part of the brain were determined using a semi-quantitative RT-PCR analysis. Results. AR and ERβ levels in males were higher in the forebrain and midbrain than in the hindbrain. In females, AR and ERβ levels were higher in the forebrain than in the midbrain and hindbrain. AR levels in the forebrain and midbrain of males were higher than those of females. Conversely, there was no difference in ERβ level between males and females. Conclusion. These data on hormone receptors provide the foundation for understanding the molecular basis of AR and ERβ mRNA expression levels in medaka brains. In addition, our results suggest that, in Japanese medaka, AR, but not ERβ, expression may exhibit sexual dimorphisms between males and females in the forebrains and midbrains.
We evaluated impact of DDT isomers, o, p'- DDT [1, 1-dichloro-2, 2-bis (p, p'-chlorophenyl) ethylene] and p, p'-DDT [1, 1, 1-trichloro-2, 2-bis (p-chlorophenyl) ethane], and their metabolites, o, p'-DDE and p, p'-DDE, on ovarian steroidogenesis. All these compounds, except for p, p'-DDT, demonstrated estrogenic effects on steroid secretion in co-cultures of porcine prepubertal granulosa and theca cells. p,p'-DDT decreased progesterone and estradiol release, which was reversed by the addition of testosterone. In contrast, o, p'-DDT inhibited progesterone secretion with parallel stimulation of basal and testosterone-stimulated estradiol release. DDEs stimulated progesterone and estradiol secretion. The fluorometric assay confirmed that p,p'-DDE, o,p'-DDT, and o,p'-DDE stimulated aromatase activity. Western blots indicated that o,p-DDT and o,p'-DDE diminished the expression of estrogen receptor ß (ERß). This study demonstrated the isomer-dependent action of DDT in pig ovarian cells. We propose that DDT could disrupt ovarian steroidogenesis either by interfering with main steroidogenic enzymes or affecting ERß.
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