Histochemical demonstration of estrogen and progesterone binding in endometriotic tissue and in uterine endometrium: A comparative study.

Estrogen and progesterone binding to endometriotic and endometrial tissue was studied histochemically using estradiol and progesterone fluorochrome derivatives (E2-bovine serum albumin-fluorescein isothiocyanate and progesterone-bovine serum albumin-tetramethylrhodamine isothiocyanate). Thirty endometriotic samples from 21 women were studied, together with endometrial specimens obtained simultaneously from 14 of the women. In 77% of the endometriotic samples binding of the estrogen conjugate was indicated by specific fluorescence in more than half of the epithelial cell population, and in 20% in less than half. The corresponding figures for the progesterone conjugate binding were 75 and 18%, respectively. Blocking studies indicated a reasonable degree of ligand specificity. In endometrial tissue the corresponding figures were 64 and 29%, respectively, for binding of the estrogen conjugate and 54 and 38%, respectively, for binding of the progesterone conjugate. In 7 of 13 cases where evaluable samples of both tissues had been obtained, the relative proportion of fluorescent cells, with either reagent, was similar in the two tissue types. Our results suggest that the cytoplasm of epithelial cells in endometriotic tissue and in uterine endometrium contains specific binding sites for both estrogen and progesterone. The binding pattern of the two conjugates in endometriotic tissue was unrelated to the menstrual phase.