250. Adult exposure to dietary phytoestrogens reduces fertility of male rats

Abstract

Phytoestrogens are plant-derived compounds that are particularly abundant in soy-based foods. Exposure to exogenous oestrogenic chemicals has been implicated in declining male fertility. The aim of this study is to deduce whether adult phytoestrogen exposure affects the reproductive function of male rats, and by what mechanisms phytoestrogens may be acting.

Six male rats were transferred from a low soy diet (control) to an experimental high soy diet, while nine males remained on the control diet. On days 3, 6 and 12 all males were mated and litter sizes recorded. A second group of male rats kept on the same dietary regimen were killed after 3, 6 or 12 days on the diets. The epididymides were collected from the rats. Real-time PCR was performed to measure mRNA quantities of oestrogen receptors alpha (ERα) and beta (ERβ), and androgen receptor (AR). The TBARS assay for lipid peroxidation was performed on epididymal sperm samples from rats fed the high or low phytoestrogen diet for 3 days.

The average litter size following 3 days on the high soy diet was significantly lower than that for rats maintained on the control diet. Litter sizes returned to control levels by day 12. ERα and AR expression decreased in the cauda region of the epididymis following 3 days on the high soy diet, but returned to control levels by day 6. Lipid peroxidation of epididymal sperm was increased in rats fed the high phytoestrogen diet for 3 days.

Short-term exposure to high phytoestrogen levels transiently reduces male fertility, and alters hormone receptor expression. Endocrine disruption may impair fertility by reducing antioxidant protection of sperm stored in the epididymis.