Immunohistochemical detection of estrogen receptors in the canine uterus and their relation to sex steroid hormone levels

Cyclic changes in estrogen receptor expression in the uterine tissue of 60 female dogs were evaluated, using an immunohistochemical technique on forma lin-fixed paraffin-embedded sections. The expression of estrogen receptors in the uterine hems, body and cervix was quantified by means of an immunohi stochemical score. A negative correlation was found between staining scores in the uterine horns and serum progesterone levels. Generally, staining sc ores in the uterine hems were highest during proestrus, declined during est rus and were lowest during early metestrus. During anestrus high staining s cores for estrogen receptors were observed, indicating sensitivity for estr ogens in a sexual quiescence stage. Compared with the uterine horns, high s taining scores were found in the uterine body and cervix during estrus and metestrus. No positive staining for estrogen receptors was detected in 1 pr egnant uterus. Fluctuations in estrogen receptors were more pronounced in e ndometrial stroma cells than in epithelial cells of the uterine hems. The i mportance of stromal cells in the sexual cyclicity of the canine uterus sho uld not be underestimated when studying uterine endocrinology and pathology . (C) 1999 by Elsevier Science Inc.