Macrophages in the Corpus Luteum of the Rat : Immunohistochemical and Transmission Electron Microscopic Study

Kim, Wo Sik; Han, Seung Ro; Cho, Geun Ja; Kim, Soo Il; Park, Chang Sik

Abstract

Macrophages in the corpus luteum have many important roles during the periods of functional development and luteal regression. Not only phagocyte the apoptotic luteal cells, but also they secrete many cytokines and exert their effects via autocrine/paracrine actions.In this study, we investigated the changes of number and immunoreactivity of macrophages at various developmental periods of the corpus luteum in the rat ovary. The rats (Sprague-Dawley strain, female)at age of 8 weeks (ovulatory period), GD 6 (pregnant period), and postpartum 5 days (postpartum period)were sacrificed under ether anesthesia and obtained both ovaries, one used for macrophages immunohistochemistry and the other used for TEM. The results were as follows; 1.In the corpora lutea of the rat, macrophages were observed all the developmental periods including ovulatory, pregnant and postpartum periods. 2.In the corpora lutea of the rat, number of macrophages was highest in the ovulatory period, and decreased at postpartum period and pregnant period in order. The immunoreactivity of macrophages was high at ovulatory period, moderate at postpartum period, and low at pregnant period. 3.In TEM observations, two types of macrophages were observed: One type was non-phagocytic macrophage and the other type was phagocytic macrophage. Phagocytic macrophages were observed in the corpora lutea at ovulatory and postpartum periods and contained apoptotic bodies, phagocytic vacuoles and many lipid droplets. Non-phagocytic macrophages were observed in the corpora lutea at pregnancy period and showed slender cell body with long cytoplasmic processes and contained no apoptotic bodies. In the rat, the number and the degree of immunoreactivity of macrophages in the corpus luteum varied with the changes of functional state of the corpus luteum. It was suggested that the main function of the macrophages at the ovulatory and postpartum periods was elimination of apoptotic luteal cells and that at pregnancy period was autocrine/paracrine action.Ultrastructurally, two types, phagocytic and nonphagocytic types, of macrophages confirmed. These results will provide valuable informations on the study of the role macrophages during development and regression of corpus luteum.