Fig. 1. Experimental design.

Timed-pregnant Fischer (CDF) rats were injected (ip) with daily 20 μg/kg (low dose MXC) or 100 mg/kg MXC (high dose MXC), 1 mg/kg EB (EB), or vehicle (DMSO:sesame oil; 1:2; Control) between 19 and 22 day post coitum (dpc) (sperm-positive vaginal smear day = 0 dpc). After birth, the female offspring were injected daily (sc) with the same treatments between postnatal day (PND) 0 and 7. In the first experiment, animals were monitored daily for the vaginal opening starting PND 25, for the first estrus using vaginal cytology, and for regularity of the first cycle. On the proestrus day of the 3^rd cycle, animals in each treatment group were divided into two groups. In one group, ovaries were collected for histology and immunohistochemistry. Serum was collected for hormone measurement by radioimmunoassay (RIA). The other group was bred to assess pregnancy rate and litter size; and after birth, the dams’ cycles were followed until 12 months of age to determine any premature reproductive aging. In another experiment, a separate group of timed-pregnant females were treated, superovulated, and the number of oocytes released was determined as described in Materials and Methods. N= 5–9 from 3–5 litters in each experiments. Critical ovarian processes that occur during the treatment period are shown in a gray box below the time line.