ESTROGEN-RECEPTORS AND PROGESTERONE-RECEPTORS IN NORMAL CYCLING ENDOMETRIUM AS STUDIED BY END-POINT TITRATION

A thorough knowledge of the normal physiological fluctuations in estro gen- (ER) and progesterone receptors (PgR) is essential to characteriz e the changes in ER and PgR in the abnormal endometrium. We investigat ed the distribution of ER and PgR in frozen human cycling endometrial tissue using the commercially available ER- and PgR-ICA kits. Two-fold end-point titration (EPT) of ER and PgR antibodies was implemented to semi-quantitate more accurately ER and PgR. Semiquantitation of ER an d PgR using EPT was significantly correlated to results obtained using either simple scoring or enzyme-immunoassay (EIA) methods. ER and PgR staining fluctuated in relation to the menstrual cycle. In most subph ases PgR exceeded ER in both epithelial and stromal cells. Highest lev els of ER and PgR were demonstrated in the glands of the functionalis in mid-to-late proliferative phases, whereas both receptors were almos t undetectable by immunohistology in the glands of mid-to-late secreto ry phases. Endometrial stromal cells had high and nearly constant EPT values for PgR, but low values for ER througout the menstrual cycle. E PT values for ER and PgR were generally higher in the basalis than in the functionalis but showed similar cyclic fluctuations. Our results f urther substantiate the view that the response to hormonal stimulation is cell-type specific, and suggest differences in steroid metabolism according to cell type and layer.