Immunohistochemical analysis of oestrogen and progesterone receptors of eutopic and ectopic endometrium in the rabbit model of endometriosis: the effect of pregnancy.

Oestrogen receptors (ER) and progesterone receptors (PR) were measured in the rabbit model of endometriosis in eutopic and ectopic endometrium of pregnant animals (n = 7) and controls (n = 7). Immunostaining of cryostat sections of ectopic and eutopic endometrium was performed using monoclonal antibodies against ER and PR. Levels of ER and PR were 'evaluated' in a semi-quantitative manner using a modified histoscore. The ER and PR content in stromal and glandular cells was not different in eutopic and ectopic endometrium in either pregnant or non-pregnant control animals. There was a significant difference between the PR content of the glandular epithelium of pregnant animals and controls for both eutopic (P less than 0.02) and ectopic (P less than 0.001) endometrium. The disappearance of glandular PR and the persistence of stromal PR suggest that the function of the glandular endometrium is mediated by the paracrine and autocrine action of stromal cells. The decidual cells are likely to produce substances that may be of importance in embryo implantation and early pregnancy.