Effects of chronic dietary exposure to genistein, a phytoestrogen, during various stages of development on reproductive hormones and spermatogenesis in rats.

Developmental, hormonal, and gametogenic parameters were evaluated in male progeny following chronic dietary exposure to the phytoestrogen genistein. Twenty pregnant rats were fed a diet containing genistein (50 microg/d) from d 17 of gestation, and 12 were fed a control diet without genistein. Four litters each of control and genistein-fed rats were euthanized on d 21. The remaining pups were weaned on d 21 and only male rats were used in this study. On d 21, eight litters of genistein-fed rats were placed on control diet (gestational and lactational exposure alone [GL-G]), and the remaining eight continued on genistein diet (lifelong exposure group [LL-G]). These rats were euthanized (four litters/group) on d 70 or 130 of life. Serum testosterone, which was slightly reduced in genistein-exposed rats on d 21, did not differ among treatment and control groups on d 70 and 130. Serum luteinizing hormone of genistein-exposed rats was reduced on d 21 and 130, but not on d 70. Serum follicle-stimulating hormone did not vary among groups at any age. Treatment-related effects of dietary genistein were not observed on the weights of the testes of 21-d-old rats. Except for a slight decrease in testis weight of GL-G rats at 130 d, no significant effect of dietary exposure was observed on the weight of the testes in any other group. However, epididymal weights were significantly reduced in both treated groups at d 130. Testicular sperm count (on d 70 as well as 130) also was not affected in GL-G or LL-G rats. We conclude that gestational plus lactational exposure to genistein and subsequent dietary exposure to genistein have no adverse effects on gametogenic function in male rats.