ABSTRACT
The relevance of steroid receptors in both normal prostate and in prostatic pathology is
well recognized, but tissue-specific distribution of some of them in the different cell
compartments of the canine prostate gland is not completely characterized. We analysed
the immunohistochemical expression of androgen (AR), oestrogen α (ERα) and β
(ERβ) and progesterone (PR) receptors in the different cell types of the canine prostate
gland, either normal or with different pathologic conditions (hyperplasia, prostatitis,
carcinoma). AR labelling was 100% in the epithelial cells of normal and hyperplastic
tissue, 74% in prostatitis, and 65% in carcinomas. ERα was 85% in normal cases, 35%
in hyperplastic cases, 22% in inflamed cases, and 12% in neoplastic glands. ERβ
expression was 85% in normal cases and around 70% in all of the pathological
conditions. On the other hand, PR expression was weak and less common in normal
tissue (44%), when compared to hyperplasia and other diseases. Overall, the expression
of AR, ERα and ERβ was highest in normal glands, and decreased in hyperplasia,
prostatitis, and cancer. In dogs, the combined administration of oestrogen and
androgens synergistically increases prostate weight, and continued treatment leads to
the development of glandular hyperplasia. The aim of the present study was to examine
the immunohistochemical expression of AR, ERα, ERβ and PR in a model of
experimentally induced canine prostatic hyperplasia. Five male Beagle dogs were
castrated and treated with 25 mg of 5α-androstane-3α, 17β-diol and 0.25 mg 17β-
estradiol for 30 weeks. Prostate specimens were surgically obtained every 6 weeks
(experimental stages M0 to M6). The control group consisted of three non-castrated
dogs treated with vehicle, from which specimens were only taken at the time points M0,
M1, M4 and M6. Immunohistochemical data revealed high AR and ERα expression in
the epithelial and stromal cell nuclei of all the experimental and control specimens. The
suspension of hormone treatment led to a significant reduction in the expression of both
receptors. On the contrary, ERβ was only expressed in epithelial cell nuclei, with no
significant differences in the percentages of stained nuclei between control and
hormonally treated or atrophic prostates. Weak staining for PR was observed in a small
proportion of epithelial cell nuclei but not in stromal cells. Results indicate that AR,
ERα, ERβ and PR are differently expressed in canine prostate tissue. In addition, the