OBJECTIVETo evaluate the effects of neonatal exposure to different doses of bisphenol A (BPA) on the vaginal opening day (VOD), hypothalamic Kiss-1 mRNA expression, and ovarian estrogen receptor (ER) mRNA expression in female rats.

METHODSNeonatal female Sprague-Dawley (SD) rats were randomly divided into six groups: blank control, vehicle, 17β-estradiol (17β-estradiol, E2, 10 μg/d), low-dose BPA [25 μg(kg·d)], medium-dose BPA [50 μg(kg·d)], and high-dose BPA groups [250 μg(kg·d)]. The rats were subcutaneously injected with respective agents on postnatal days 0-6. The VOD was recorded, and each rat was sacrificed on the same day. The hypothalamus and ovary were taken and weighed, and the organ coefficients of hypothalamus and ovary were calculated. The hypothalamic Kiss-1 mRNA expression and ovarian ERα and ERβ mRNA expression were measured by real-time PCR.

RESULTSCompared with the control group, the E2 and medium- and high-dose BPA groups had advanced VOD, and the E2 group had significantly reduced hypothalamic Kiss-1 mRNA expression and ovarian ERβ mRNA expression (P<0.05).

CONCLUSIONSNeonatal exposure to medium- and high-dose BPA[50 and 250 μg/(kg·d)] can induce precocious puberty in rats, but it may not result from the change in hypothalamic Kiss-1 mRNA expression. Neonatal exposure to low-dose BPA [25 μg/(kg·d)] does not induce precocious puberty in rats.