[Effects of progesterone antagonists on the eosinophilic granulocytes in the rat uterus].

An effect of estrogen in the uterus of rats is the invasion of eosinophil granulocytes into the endometrium and the myometrium. Progesterone prevents the estrogen induced eosinophilia. In the uterus the eosinophils degranulate, probably mediated by steroid hormones. The extent of infiltration with eosinophils may allow estimation of the estrogen activity of drugs. The present study investigates the effects of a long-term treatment with the progesterone antagonists Onapristone and ZK 112.993 on the eosinophils in the uterus of intact mature rats. The visualization of the eosinophils was done immunohistochemically with an antiserum against the Major Basic Protein (MBP) localized in the secondary granules. The localization of this protein in the extracellular matrix immediately beneath the eosinophils in Carnoy-fixed uteri was taken as a marker for their degranulation (Duchesne and Badia 1992). Onapristone caused a strong infiltration by eosinophils which corresponds to those seen in ovariectomized rats treated with estrogen, while the effect of ZK 112.993 was clearly weaker. This is in agreement with the lower antiprogestational activity of ZK 112.993 also found with other endpoints. In uteri fixed in Bouin' solution the immunoreactivity of the eosinophils was strongest and restricted to these cells. However, after Carnoy' fixation the antibody reacted with the extracellular matrix beneath the eosinophils while the staining intensity of the cells was decreased. Our results do not support the idea of a substantial extracellular deposition of MBP in the uterus of rats but speak in favour of a permeabilization of the eosinophil membranes by alcohol containing fixatives allowing granule contents to leave the cell.