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Bisphenol A Increases Progesterone Receptor Immunoreactivity in the Hypothalamus in a Dose‐Dependent Manner and Affects Sexual Behaviour in Adult Ovariectomized Rats
Author(s) -
Funabashi T.,
Sano A.,
Mitsushima D.,
Kimura F.
Publication year - 2003
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1046/j.1365-2826.2003.00872.x
Subject(s) - ovariectomized rat , endocrinology , medicine , hypothalamus , preoptic area , endocrine disruptor , subcutaneous injection , immunocytochemistry , bisphenol a , receptor , endocrine system , estradiol benzoate , chemistry , estrogen receptor , estrogen , biology , hormone , organic chemistry , cancer , breast cancer , epoxy
Abstract Recently, we reported that bisphenol A (BPA), an endocrine disrupter, increased progesterone receptor (PR) mRNA in the preoptic area (POA) in adult ovariectomized rats. In the present study, we examined whether BPA also induced expression of PR proteins in both the POA and the ventromedial hypothalamic nucleus (VMH), and whether those proteins were involved in the induction of sexual behaviour. Two weeks after ovariectomy, rats received a subcutaneous (s.c.) injection of BPA, 17 β ‐oestradiol or vehicle. Twenty‐four hours after the injection, the rats were killed and their tissues were examined by immunocytochemistry. Some rats that received a s.c. injection of BPA, E 2 or vehicle alone on the day before were injected with progesterone at 15.00 h and examined for sexual behaviour 5–7 h later. As expected, injection of 10 µg E 2 significantly increased the number of PR immunoreactive cells in both the POA and the VMH compared to the number after injection of vehicle alone. In both the POA and the VMH, injection of BPA at a dose of 10 mg also significantly increased the number of PR immunoreactive cells compared to the number after injection of sesame oil alone. Furthermore, BPA induced a dose‐dependent increase in the number of PR immunoreactive cells in both the POA and the VMH, demonstrating that the number of PR cells was significantly increased by as little as 100 µg of BPA. Ovariectomized (OVX) rats that were primed with 10 mg of BPA, followed by 1 mg of progesterone, displayed mainly rejection behaviour, but not lordosis as typically observed in OVX rats primed with E 2 followed by progesterone. The present study suggests that BPA influences reproductive functions, including sexual behaviour even in adulthood, by altering the PR system in the hypothalamus.