Abstract
In order to investigate ovarian function during the early stage of pregnancy in superovulated animals, the effects of ovariectomy on development and recovery rate of ova were studied in 3-5 month old Wistar rats treated with 50 iu PMSG s. c. followed later by 50 iu HCG s. c. 52h. All the treated animals were mated with fertile males. The mean number of ova shed in the treated rats was about 2.5 times that of the controls. The rate of ova with pronuclei at 10:30-12:00 on Day 1 of pregnancy in the treated rats (90.2%) was not different from that of the controls (92.6%). When the animals were ovariectomized on Day 1, 2 or 3 of pregnancy and were given 4mg progesterone s. c. daily up to Day 5 of pregnancy, the numbers of ova recovered on Day 5 in the treated animals exceeded significantly those in the control groups. The recovery rate of ova in the superovulated-intact rats (21.7%) was lower than that of non-treated control (66.7%) or superovulated rats ovariectomized on Day 1, 2 and 3 of pregnancy (33.3-43.2%). Although most of the ova obtained from the uteri of superovulated rats had developed to blastocyst (67.4-92.6%) at 1400hr on Day 5 of pregnancy, higher rate of zona shedding and greater size of blastocyst with zona pellucida were shown in the superovulated-intact rats. In addtion, large vesicular ova- rian follicles were recognized in all of the superovulated animals at autopsy on Day 5. It is suggested that the treatment of rat ovaries with PMSG and HCG may influence adversely the development and viability of ova in the genital tract during early pregnancy.
