EFFECTS OF DIETARY SOYBEAN ESTROGENS ON THE REPRODUCTIVE-TRACT IN FEMALE RATS

The estrogenic actions of dietary phytoestrogens have raised concerns regarding the potential DES-like developmental effects on the female g enital tract, but the growing evidence of cardioprotective benefits of dietary soybean estrogens provides the impetus to assess the effects of these compounds in adult female models of the menopause, We conduct ed an experiment in ovariectomized rats to determine the independent e ffects of dietary soybean estrogens (SEE) and the interactions of thes e agents with the commonly used pharmaceutical estrogen preparation (c onjugated equine estrogens, GEE) in the vagina and uterus, We looked a t the effects of SEE and GEE, alone and in combination, on uterine wei ght, body weight, vaginal cytology, uterine luminal epithelial height, and immunohistochemical staining for proliferating cell nuclear antig en (PCNA), lactoferrin (Ltf), and apoptosis, Ovarlectomized rats were fed diets containing casein or soybean protein (SEE, low dose = 11.6 m g isoflavones/1800 cal; high dose = 117.8 mg/1800 cal), with no GEE, l ow dose OFF (0.313 mg/1800 cal), or high dose CEE (0.625 mg/1800 cal) added, In this study, SEE did not demonstrate estrogenic activity for uterine weight or vaginal cytology, We also found no estrogenic effect s of these doses of SEE for PCNA, apoptosls, Ltf staining, or for LEH measurements. In addition, our results regarding the interactions of S EE and CEE do not show any evidence that the combination is additive i n effect, On the contrary, the LEH response induced by low levels of G EE, was reduced by high levels of SEE. Furthermore, the Ltf response i nduced by OFF also was reduced by high levels of SEE. This suggests th at high doses of SEE may antagonize the estrogen-agonist actions of lo w doses of CEE in the rat uterus, Our results in the ovariectomized ra t model of menopause suggest that dietary soybean estrogens will not e licit a pattern of effects that simply recapitulates those of steroida l estrogens.