OBJECTIVETo investigate the effects of pre- and post-natal exposure to soy isoflavones (SIF) on the related indicators of the reproductive system development and ER-beta expression in male rat offspring.

METHODSPregnant SD rats were randomly divided into a corn oil group (control), 3 SIF groups (50, 200 and 400 mg/kg body weight), and a diethylstilbestrol (DES, 0.1 mg/ kg body weight) group to be treated respectively by intragastric gavage from pregnancy day 0. On postnatal day (PND) 21, the male offspring were treated in the same manner till sexual maturity, and on PND 49 and 90, 6 male rats from each group were killed for observation of the related indicators of the reproductive system development and the detection of the expression of ER-beta in the testis.

RESULTSThe mean daily food intake showed no evident differences among the SIF and DES groups, but the food efficiency ratio (FER) was significantly decreased in the 200 and 400 mg/kg SIF and 0.1 mg/kg DES groups (P < 0.05) at 49 and 90 PND. At the dose of > or = 50 mg/kg, SIF markedly reduced the body weight of the rats (P < 0.05), even more so at 90 PND than at 49 PND. The increased dose of SIF was correlated with the reduction of testis weight, sperm head count and daily sperm production, and so was it with the elevation of the ER-beta expression, both more obviously at 90 PND than at 49 PND.

CONCLUSIONPre- and post-natal exposure to SIF affects the reproductive system development of male rat offspring, and the elevation of ER-beta expression may be one of its mechanisms.