Effects of genistein on ovarian follicular development and ovarian life span in rats.

Recently, studies reported that neonatal genistein treatment inhibited breakdown of oocyte nests and increased oocyte survival, resulting in multi-oocyte survival in adult mice. However, whether the inhibition effect in ovarian follicular development exists also in other stages during ovarian development (e.g. adult or climacteric) is unknown. So far, few studies have investigated the effect of genistein in adult or pre-menopausal ovarian follicular development and follicular reserves. We investigated ovarian follicular development in 4-month and 15-month-old rats after 4 weeks and 4 months treatment with genistein in a dose of 160 mg/kg d. Genistein-treated rats obtained a higher percentage of primordial follicles by 4 months of age and a greater number of surviving follicles at 15 months of age compared to a control group (P<0.05). In addition, vaginal cytology showed that age-dependent cessation of regular estrus was delayed for 2 months in the genistein-treated group than control group. These results suggest that genistein alters rat ovarian follicular development and increases the number of surviving follicles, which may prolong ovarian reproductive life.