No document available.
Abstract :
[en] Aim: Our society is facing a public health problem linked to the production of endocrine disrupting chemicals (EDCs) (1). In our laboratory we have shown that an early postnatal exposure to a very low dose of bisphenol A (BPA) disrupts sexual maturation and pubertal timing (2). However, the long-term and adult effects of such low doses have not been studied.
Methods: one day-old and 90 day-old female rats received daily subcutaneous injections of corn oil (vehicle) or BPA (25ng/kg/day or 5mg/kg/day) for 15 days. For early postnatal exposure, estrous cyclicity was followed until P105 when folliculogenesis was studied. For adult exposure, estrous cyclicity was followed from two weeks before to four weeks after the exposure. Folliculogenesis was studied both 24h and 30 days after the adult BPA exposure. GnRH frequency was measure 24h after the adult BPA exposure.
Results: early postnatal exposure to both BPA doses significantly decreased the percentage of females with a regular cycle (BPA-25ng: 51±15%; BPA-5mg: 7±7%; OIL: 86±2%). Folliculogenesis showed a significant decrease in the number of primordial follicles (BPA-25ng: 15.5±3.6; BPA-5mg: 20.4±5.2; OIL: 71.2±14.1) as well as a disruption in atretic follicles (BPA-25ng: 26.5±3.9; BPA-5mg: 111.9±29.4; OIL: 48.8±10.3) and the presence of cysts follicles (BPA-25ng: 0.04±0.02; BPA-5mg: 0.3±0.1). Adult exposure to BPA caused a disruption of the estrous cycle characterized by a significant decrease in the average time spent in proestrus (BPA-25ng: 19±2%; BPA-5mg: 17±1%; OIL: 23±1%). We also observed a disruption of folliculogenesis characterized by a significant decrease of antral follicles (BPA-25ng: 0.4±0.1; BPA-5mg: 0.5±0.07; OIL: 1.54±0.2), an increase of atretic follicles (BPA-25ng: 50.8±7.7; BPA-5mg: 48.7±6.7; OIL: 31.3±5.4) and the presence of cysts follicles (BPA-25ng: 0.2±0.1; BPA-5mg: 0.06±0.02). This effect was transient as the exposed females showed a regular cycle and folliculogenesis one month after the last dose of BPA. GnRH interpulse interval was significantly different when comparing animals exposed to the high or low dose of BPA but not when compared to the control group (BPA-25ng: 42.6±0.5; BPA-5mg: 40.2±0.6%; OIL: 41.1±0,2minutes±SEM).
Conclusion: both early postnatal and adult exposure to BPA disrupts the estrous cycle and folliculogenesis. However, while adult exposure produces persistent alterations, the adult exposure cause activational effects.