Neonatal exposure to estrogen in the Wistar rat decreases estrogen receptor-beta and induces epithelial proliferation of the prostate in the adult.

Background/aims: The effects of environmental endocrine disruptors on the male reproductive system have received much attention. We attempted to assess the responsible reproduction period vulnerable to decrease in ER beta mRNA by exposing neonate rats to disruptors.

Methods: Each of 64 male Wistar rats was given an injection of estradiol at a dose of 25 mug or oil on days 1, 3 and 5 after birth. These rats were sacrificed on days 80, 120, 160 and 180 and then subjected to measurements of both serum and tissue testosterone levels. Real-time quantitative polymerase chain reaction (PCR) was used to measure the levels of androgen receptor (AR) and estrogen receptor-beta (ER beta) mRNA of the ventral prostate. Histological compositions were analyzed by quantitative morphometry. Immunohistochemical analysis of proliferating cell nuclear antigen (PCNA) was determined.

Results: The incidence of epithelial components by histomorphometry and the expression of PCNA was significantly higher in the estrogen group in the mature adult (day 160). Levels of AR and ER beta mRNAs in the estrogen group were significantly lower in middle-aged rats (day 180).

Conclusion: Estrogen exposure in the neonatal period to Wistar rats decreases the number of ER beta in the mature adult and accelerates cell proliferation.