Immunohistochemical study of canine mammary steroid receptors in various mammary conditions

Abstract

To evaluate immunolocalization of ERα and PR in mammary gland of bitch in different stages of the estrus cycle (EXP 1), to evaluate the correlation between immunolocalization of ERα and PR in normal mammary tissue and mammary tumor in the same dogs (EXP 2) and to evaluate the effect of deslorelin on ERα and PR on canine mammary tissues (EXP 3). EXP. 1. In the cross-sectional study, mammary tissues were collected from 24 different mixed breed bitches at 4 different stages of the estrous cycle which were; proestrus, estrus, diestrus and anestrus. For longitudinal study, mammary tissues were collected from 5 beagle bitches and at 6 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 ABC method and ERα and PR scores were calculated. The lowest scores of ERα and PR were found at diestrus in both groups. During estrus and proestrus the ERα and PR scores were significantly high. High score of the PR during anestrus was also observed in both groups. For the correlation with the levels of ovarian steroid hormone, the negative correlation between ERα and PR scores, and serum progesterone levels were found. This finding indicated that the expression of the ERα and PR was under the regulation of the ovarian steroid hormones which changed during different stages of the estrous cycle. EXP. 2. Twelve tumoral and contralateral normal mammary tissues, both determined by histology, were surgically obtained from 12 dogs. The expressions of ERα and PR were evaluated by avidin-biotin-peroxidase complex (ABC) method and ERα and PR scores were calculated. The expressions of ERα and PR between normal and tumoral mammary tissues were not significantly different which suggested similar regulation of both steroid receptor expressions between normal and tumoral mammary gland within the same bitch. A positive correlation was found between the number of the ERα and the PR in both normal and tumoral mammary tissues which may indicate that either ERα or PR could be used as a prediction of hormonal therapy parameter in dogs. EXP. 3. Twenty four bitches during anestrus were selected and devided into 2 groups, twelve bitches were implanted with placebo (untreated group) and the rest were implanted with 10 mg deslorelin (treated group). Mammary tissues were collected at 1 week before and 1, 2 and 12 weeks after implantation. The expression of ERα and PR were evaluated by ABC method and ERα and PR scores were calculated. The significantly highest score of ERα and PR were found at 2 week after implantation. When compared between groups, ERα in treated group was significantly higher than in untreated group at 2 weeks after implantation, PR score in untreated group were significantly higher than in treated group at before and 1 week after implantation. This finding demonstrated that deslorelin has the effects on steroid receptor expression in canine mammary tissue. Moreover, similar pattern on the expression of ERα and PR was found after deslorelin implantation, in which ERα and PR were up-regulated in the stimulation stage and down-regulated in the quiescent stage