Neonatal treatment with Bisphenol A decreased cell proliferation and GnRH expression in adult rat ovary.

BOURGUIGNON NS; FERNANDEZ MO; LUX LANTOS V; LIBERTUN C

San Diego CA

Congreso; ENDO 2010; 2010

The Endocrine Society

Neonatal treatment with Bisphenol A decreased cell proliferation and GnRH expression in adult rat ovary.   NS Bourguignon1, MO Fernandez1, VAR Lux Lantos1, C Libertun1, 2. Lab. Neuroendocrinology, Instituto de Biología y Medicina Experimental, Buenos Aires, 1428;  Argentina. Dept Physiology, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, 1121; Argentina   Bisphenol A, (BPA), is a xenoestrogen that alters several functions in different species, including rats and humans. In previous works we described de effect of this estrogenic endocrine disruptor on the gonadal axis of female rats (1). Following this research line, here we analyzed the effects of neonatal exposure to BPA on granulosa and theca cell proliferation, as well as GnRH expression, in ovaries of adult rats.   My M Female Sprague-Dawley rats were injected sc, daily from postnatal days (PND)1 to 10 with BPA: 500 µg/50 µl oil (H), or 50 µg/50 µl oil (L), or solvent as control (C). In adults (120-160 PND), killed by decapitation in the morning of estrus following Institutional Ethical Standards, one ovary of each animal was immediately fixed in 5% neutral buffered formaldehyde for histological examination. Cell proliferation in early preovulatory follicles was determined in ovary sections by immunohistochemical determination of the proliferating cell nuclear antigen (PCNA) in theca (TC) and granulose(GC) cells, as described in (2). Results were expressed as PCNA positive cells/total cells. In the second ovary, GnRH mRNA levels were determined using real-time PCR as described in (3). Results were expressed as means ± SE and considered significant when p<0.05. Data were analyzed by one-way analysis of variance.   Results. Animals treated with the higher dose of BPA showed a decrease of granulosa [C: 51.42±3.45 (n:5); L: 39.75±6.92 (n:5); H: 17.20± 3.54 (n:5), p<0.001] and theca [C: 42.46±3.58 (n:5); L 38.59±9.49 (n:5); H: 13.40± 4.15 (n:5), p<0.02] cell proliferation. A dramatic reduction in GnRH mRNA expression was found even with the lower dose [Arbitrary Units; C: 0.8136±0.1279 (n:5); L: 0.0862± 0.0333 (n:4); H: 0.0043±  0.0021(n:4), p<0.001]   Conclusion. BPA decreased ovary granulosa and theca cell proliferation, as well as GnRH mRNA expression, in ovaries of rats months after of neonatal treatment.  These results show that exposure to BPA during the neonatal period alters irreversibly reproductive parameters in the ovary. Exposure to this agent could contribute to the development of many reproductive disorders of increased incidence in humans. References.   1. Fernández M et al, Environ Health Perspect 2009;117:757-62. 2. Abramovich D et al.  Fertil  Steril 2009. In press. 3 Schirman- Hildesheim TD et al  2005. Endocrinology 146:3401-3408    Supported by Consejo Nacional de Investigaciones Científicas y Técnicas; Agencia Nacional de Promoción Científica y Tecnológica; Universidad de Buenos Aires. Argentina.