Bisphenol A (BPA) exposure in humans is widespread, and BPA has been detected in a variety of samples including follicular fluid. BPA levels have been found to negatively correlate with the developmental potential of oocytes in women undergoing in vitro fertilization and to induce meiotic abnormalities experimentally in human and mouse models. BPA may detrimentally affect oocyte maturation, and different concentrations of exposure can cause various outcomes. Because of the importance of oocyte maturation on developmental potential, disturbances during this time can significantly impact oocyte viability. Here, bovine oocytes were matured in vitro with and without BPA treatment of the media. The levels of BPA taken up by the oocytes were much lower than the initial exposure. Medium treatment with 30 ng/ml resulted in an average of 2.48 ng/ml BPA measured in mature oocytes. These oocytes exhibited decreased maturation and increased incidence of spindle abnormalities. Only 57.4% of oocytes exposed to 30 ng/ml BPA reached maturity compared to 72.4% of controls (p < 0.05). Mature oocytes following BPA exposure displayed increased abnormal spindle morphology (67.9%) and chromosome dispersal (60%) compared to all other groups analyzed (p < 0.05). Thus, exposure to BPA during in vitro oocyte maturation has the potential to decrease oocyte quality.

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Previous studies show that changes in estrogen (ER) and glucocorticoid receptor (GR) function in rainbow trout (Oncorhynchus mykiss) oocytes modulate the growth performance phenotype of embryo and juvenile progeny; the present study was undertaken to determine whether this altered growth performance is associated with changes in the expression of several growth-related genes in early-stage embryos. Unfertilized oocytes were incubated in the presence of various combinations of GR and ER agonists and antagonists; the oocytes were then fertilized and the expression of genes that encode for six nuclear receptor superfamily (NRS) proteins (GR1, GR2, ERα, ERβ, TRα, and TRβ) and the two IGF peptides (IGF1 and IGF2) were measured in the 7-, 13-, and 26-dpf embryos. By day 26 of embryogenesis, the expression of the six NRS-related genes of interest and that of igf2 were significantly enhanced in embryos reared from ER agonist- or ER antagonist-treated oocytes, regardless of whether the GR agonist, cortisol, was also included in the initial oocyte incubation medium. Conversely, the igf1 expression pattern among treatment groups was significantly enhanced in the cortisol-only treatment group and in the ER antagonist and GR antagonist groups that were co-incubated with cortisol. Additionally, in the ER agonist treatment groups igf1 expression was significantly inhibited when cortisol was included in the oocyte incubation medium. The findings show that a single in ovo exposure to the receptor agonists/antagonists markedly changed the programming of the expression of NRS-related and IGF-related genes of the early-stage trout embryos.