Estrogen receptor alpha (ERα) and progesterone receptor (PR) in the mammary gland of bitches during different stages of estrous cycle

Abstract

The objective of this study was to evaluate the estrogen receptor alpha (ERα) and progesterone receptor (PR) expressions in normal mammary tissues of bitches during different stages of the estrous cycle. Mammary tissues were collected from five beagle bitches at six different estrous stages for each bitch, which were: anestrus, proestrus, estrus, early diestrus, mid diestrus, and late diestrus. The expressions of ERα and PR were evaluated by avidin–biotin–peroxidase complex (ABC) method, and ERα and PR scores were calculated. The lowest scores of ERα and PR were found in mammary tissue collected during mid diestrus, whereas the ERα and PR scores were significantly higher during estrus and proestrus. A significantly higher score of the PR during anestrus compared to during mid diestrus was also observed, but this was not found for ERα score. In addition, positive correlation between ERα and PR scores were found which indicated that the presence of ERα and PR may be under the same regulatory mechanism. In conclusion, these findings suggested that ovarian steroid hormones, estrogen and progesterone, which differed during the stages of the estrous cycle may have a regulatory role in ERα and PR expression in bitch mammary gland.