THE ANTI-FERTILITY EFFECTS IN PREGNANT RATS OF A SINGLE INJECTION OF ESTRADIOL CYCLOPENTYLPROPIONATE

Abstract

Sprague-Dawley female rats were injected subeutaneously with varying dosages of estradiol cyclopentylpropionate (ECP) on the morning that sperm were found in the vagina. The percentage of embryos missing at 9–11 days post coitum after a single injection of 1,5 or 10 μg of ECP was 19%, 66%, 97%, respectively. Deciduomata formation was inhibited in most animals that received 10 μg of ECP but was unaffected in those receiving 1 or 5 μg. The most significant effect of 10 μg ECP was to increase tubal and uterine motility so that the fertilized ova were expelled from the uterus by 48 hours post coitum. The effectiveness of 5 μg of ECP in accelerating ova transport varied from animal to animal. These results indicate that the rate of ova transport is an especially vulnerable process in the reproductive cycle for interrupting pregnancy in the rats.