Objective To establish a pathological animal model of polycystic ovary (PCO) by letrozole in rats. Investigate whether PCO were mediated by the effect of oxidative stress by measuring oxidative stress levels in this cohort of rats with PCO, and proceed a new way of treatment for polycystic ovary syndrom (PCOS). Methods 90 SD female rats aged 6 weeks were randomly divided into two groups, including a control group of 45 rats that received vehicle only 〔1% aqueous solution of carboxmethlycellulose (CMC), 1 mL/d〕 once daily orally (p.o.), and an experimental group of 45 rats, which were administered letrozole at concentrations of 1 mg/kg p.o. dissolved in 1% CMC (1 mL/d) once daily. The treatment period was 28 d. During this period, vaginal smears were collected daily for estrus cycle determination and body masses were measured every 7 d. On the day subsequent to the last letrozole dose administration, rats were killed; Uteri and ovaries were then excised and weighed for the calculation of organ indexes. Serum hormone levels, SHBG and histologic changes in the ovaries were examined. Then
