QUANTITATIVE CHANGES IN MACROPHAGE DISTRIBUTION IN NORMAL MOUSE OVARYOVER THE COURSE OF THE ESTROUS-CYCLE EXAMINED WITH AN IMAGE-ANALYSIS SYSTEM

PROBLEM: The current study considered the distribution of macrophages within the major ovarian structures throughout the estrous cycle. METH ODS: Immunohistochemical analyses were carried out using an avidin-bio tin-peroxidase staining method and the rat anti-mouse macrophage monoc lonal antibody anti-Mac-1 was applied to stain macrophages. A computer -assisted image analysis system was used to quantify and compare the d istribution of macrophages within individual ovarian structures during the estrous cycle. The following morphological structures were analyz ed: primordial, preantral, antral, pre-Graafian, and atretic follicles ; first-, second-, and third-generation corpora lutea; and the interst itium. The analysis included follicular and corpus luteum substructure s: theca, granulosa cells, and interstitium. The system allows the est imation of macrophage distribution as a macrophage density per mu m(2) of the defined area. RESULTS: Primordial and preantral follicles did not contain macrophages during all stages of the estrous cycle. In ant ral, pre-graafian, and graafian follicles, macrophages were located an d quantified only in the theca and were not detected in the granulosa cell layer. In contrast, atretic follicles showed macrophage localizat ion in both thecal and granulosa cell layers. Macrophages were present in small numbers in the granulosa luteal cell layer and in high numbe rs in the thecal layer of newly developing corpora lutea. In the secon d generation of corpus luteum, macrophages followed the same pattern o f distribution, while old corpora lutea contained significantly higher numbers of macrophages in both thecal and luteal cell layers. Surpris ingly, significant quantitative changes in the macrophages distributio n were detected over the course of the estrous cycle. Macrophage densi ty was significantly higher in proestrus and metestrus when compared w ith the density in diestrus and estrus in most of the studied substruc tures with the exception of atretic follicles. Atretic follicles showe d high macrophage density throughout the cycle with a two-fold higher density at metestrus. CONCLUSION: Macrophages were present in the mous e ovary over the course of the estrous cycle. The greatest numbers of macrophages appearing in corpora lutea and in atretic follicles sugges t a role for macrophages in corpus luteum differentiation and follicul ar atresia. Their patterns of distribution at proestrus and metestrus within microenvironmental compartments suggests a functional correlati on with the events of ovarian development.