Estrogen-α and progesterone receptor expression in cystic endometrial hyperplasia and pyometra in the bitch

Estrogen-α receptor (ER) and progesterone receptor (PR) were examined immunohistochemically in uteri of normal bitches, in uteri of bitches with cystic endometrial hyperplasia-mucometra (CEH-M) and in uteri of bitches with endometritis–pyometra (E–P), under exogenous progesterone treatment. In the CEH-M group, the ER- and PR-scores of all uterine cell types were higher than the ER- and PR-scores of normal uteri, although these differences were not always statistically significant. The ER-scores of E–P group were significantly lower than the ER-scores of the normal uteri and CEH-M group. The PR-scores of the E–P group tended to be higher than the PR-scores of the normal uteri, except for the surface epithelium, although these differences were not statistically significant. Exogenous progesterone treated bitches with CEH-M or E–P showed reduced ER- and PR-scores in the different uterine cell types, compared with the corresponding nontreated CEH-M or E–P group. The differences in ER and PR expression between CEH-M and E–P suggest different factors in the pathogenesis of both entities. Although, these changes in ER and PR expression do not seem to be directly involved in the pathogenesis of CEH-M and E–P. It is suggested that for CEH-M and progestin induced CEH-M a hormone dependent pathway is responsible. For P, the trigger may be bacterial infection.