Abstract
The effects of unilateral ovariectomy on late pregnancy were investigated in Wistar strain rats. Animals were kept under control lighting room (light went on 6:00, Light (12 hrs): Dark (12 hrs)). The operation of unilateral ovariectomy was performed under light ether antesthesia. The animals were semi-spayed on day 18 (9:0011:00), day 19("), day 20("), day 21 (9:0011:00 or 16:0017:00) and day 22 (9:0011:00 or 12:0013:00) of pregnancy, respectively. The observation was carried out for delivery at 9:00, 12:00, 15:00 and 18:00 on every day from day 21 of pregnancy. All animals were killed the next day of delivery and the oviducts and ovaries were removed. Those weights were recorded immediately.
In the rats operated on day 18 of pregnancy, majority of animals delivered in day 23 of pregnancy. But, 50 percent of animals operated on day 19 of pregnancy delivered before 9:00 on day 22 of pregnancy. Also, large number of animals operated on day 20 of pregnancy de-livered on day 22 of pregnancy. The delivery of animals operated in another day of pregnancy was similar to the control group.
The weight of the remained ovary did not significantly increase from day 18 to day 22 of pregnancy, but, compensatory ovulation had occurred in all of the operated animals at postpartum estrus. The number of ova in rats operated at day 22 of pregnancy decreased significantly from the group operated at day 21 (9:0011:00) of pregnancy (p<0.05). When rats were unilaterally ovariectomized on day 19 of pregnancy, ovarian weights increased significantly at 48 hrs after operation (p<0.05).
It is suggested from the present study that the role of ovary during the late pregnancy changed from day 19 of pregnancy and the number of follicles ovulated in post-partum estrus should be determined between the evening of day 21 and the next morning.
