Neonatal exposure to bisphenol A reduces the pool of primordial follicles in the rat ovary

We evaluated whether exposure to bisphenol A (BPA) disrupts neonatal follicle development in rats. From postnatal day 1 (PND1) to PND7, pups received corn oil (control), diethylstilbestrol (DES20: 20 μg/kg-d, DES0.2: 0.2 μg/kg-d), or BPA (BPA20: 20 mg/kg-d, BPA0.05: 0.05 mg/kg-d). We examined follicular dynamics, multioocyte follicles (MOFs) incidence, proliferation and apoptosis rates, expression of steroid receptors (ERα, ERβ, PR, AR) and cyclin-dependent kinase inhibitor 1B (p27) in PND8 ovaries. DES20, DES0.2 and BPA20-ovaries showed fewer primordial follicles and increased growing follicles. DES20-ovaries exhibited increased incidence of MOFs. Oocyte survival, AR, PR and apoptosis were not changed. Primordial and recruited follicles from BPA20-ovaries showed higher p27, whereas ERβ and proliferation were both increased in recruited follicles. ERα positive primary follicles increased in BPA 20-ovaries. Results show that BPA reduces the primordial follicle pool by stimulating the neonatal initial recruitment, associated with an increased proliferation rate likely mediated by an estrogenic pathway.

Research highlights▶ BPA reduces the stockpile of neonatal primordial follicles. ▶ BPA exerts this reduction by increasing primordial to primary follicle transition. ▶ ERβ and proliferation were both increased in BPA-recruited follicles.