Persistent vs transient alteration of folliculogenesis and estrous cycle after neonatal vs adult exposure to Bisphenol A.

Exposure to Bisphenol A (BPA), a ubiquitous endocrine disrupting chemical (EDC) is known to produce variable effects on female puberty and ovulation. This variability of effects is possibly due to differences in dose and period of exposure. Little is known about the effects of adult exposure to environmentally relevant doses of this EDC and the differences in effect after neonatal exposure. This study aims at comparing the effects of neonatal versus adult exposure to a very low or a high dose of BPA for two weeks on ovulation and folliculogenesis and exploring the hypothalamic mechanisms involved in such disruption by BPA. One day-old and 90 day-old female rats received daily subcutaneous injections of corn oil (vehicle) or BPA (25 ng/kg/d or 5 mg/kg/d) for 15 days. Neonatal exposure to both BPA doses significantly disrupted the estrous cycle and induced a decrease in primordial follicles. Effects on estrous cyclicity and folliculogenesis persisted into adulthood, consistent with a disruption of organizational mechanisms. During adult exposure, both doses caused a reversible decrease in antral follicles and corpora lutea. A reversible disruption of the estrous cycle associated with a delay and a decrease in the amplitude of the LH surge was also observed. Alterations of the hypothalamic expression of the clock gene Per1 and the novel reproductive peptide Phoenixin indicated a disruption of the hypothalamic control of the preovulatory LH surge by BPA.