The Effects of Prostaglandin F2α on the Structure and Function of the Rabbit Ovary1

Abstract

Ovaries from control and prostaglandin F_2α (PGF_2α) treated pregnant rabbits were examined by light and electron microscopy. Eighteen rabbits were randomly assigned in pairs to either Days 8, 14, or 21 of pregnancy. One animal of each pair was treated with PGF_2α and the other was given an equivalent amount of vehicle. On the day of sacrifice, the ovaries and the uterus were prepared for microscopic examination. The observations from both of these organs were then correlated with peripheral progestin levels before and after treatment. Results indicated that PGF_2α causes corpus luteum involution but the degree of degeneration varies with the stage of pregnancy. Although progestin levels decrease in all treated animals, the luteal cells at Day 14 show the greatest morphological changes as most cells contain distorted structures. During early and late pregnancy the initial stages of regression are characterized by the appearance of autophagic vacuoles. The interstitial cells and follicles of the treated animals are similar to the controls. Some variation in size and number of interstitial cells is seen but this is also characteristic in the nontreated rabbits. The effect of PCF_2α on the uterus depends on the stage of pregnancy. The Day 21 animals abort and variable results are observed at Days 8 and 14. These data show that progestin levels can decrease prior to any significant morphological change, and that luteal cells specifically are responsive to PCF_2α treatment, as other ovarian compartments are not structurally affected.