The effect of estradiol-17β on ovum transport in rats was characterized by determining dose-response curve, latency and duration of effect. The relationship between plasma levels of estradiol, accelerated transport and reduced fertility was also examined. Estradiol was given as a single s.c. injection on Day 1 of pregnancy. Groups of 5 animals were sacrificed between 0-94 h following treatment, to determine distribution of eggs in the genital tract and estradiol levels in plasma. Groups of 15 rats were sacrificed on Day 12 of pregnancy to determine the number of embryos implanted. Ovum transport through the oviduct was accelerated between 11-23 h following estradiol injection in all groups: 0.5, 1, 5 or 25 μg estradiol-17β produced acceleration of 25, 89, 90 and 94% of ova that passed prematurely from the oviduct to the uterus, respectively. Non-accelerated ova were transported to the uterus at the normal time. Accelerated transport through the oviduct was accompanied by expulsion of eggs through the vagina. The mean number of implanted embryos on Day 12 of pregnancy was almost identical to the mean number of eggs remaining in the tract after the acceleration phase was completed. Maximal levels of estradiol in plasma were attained 10 h before the onset of acceleration, whereas the return to basal levels bore no constant relationship to the end of acceleration. It is concluded that a short pulse of estradiol given on Day 1 of pregnancy in rats accelerates the transport of ova through the oviduct after a latency period of 11 h. This is followed by an immediate expulsion of eggs from the tract leading to inhibition of fertility, which is quantitatively related to the number of ova expelled. Eggs that are not accelerated are transported and develop and implant normally. The rat can provide a model of fertility inhibition due exclusively to accelerated transport of ova.
|Number of pages||5|
|Journal||Biology of Reproduction|
|Publication status||Published - 1979|
ASJC Scopus subject areas
- Cell Biology
- Developmental Biology