Immunocytochemical Localization of Estrogen Receptors in the Normal Male and Female Canine Urinary Tract and Prostate*

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Abstract
We have used the monoclonal estrogen receptor (ER) antibody H222Sp.gamma. to localize ER by immunocytochemistry in frozen sections of the normal canine urinary tract of both sexes and of the normal prostate of the male. Striking regional heterogeneity of ER location was observed. In the urinary tract, specific ER staining was confined to nuclei of the transitional epithelium (mucosa) and subjacent stroma (submucosa) of the prostatic urethra in the male dog and of the proximal urethra in the female dog. In both sexes there was a gradient of ER staining intensity along these urethral segments. In the male, ER staining intensity was highest in the region of the verumontanum. The pattern and intensity of staining were similar in the male prostatic urethra and female proximal urethra, indicating a similar concentration of ER in these tissues, which have the same embryological origin. No specific staining was found in the kidney, ureter, bladder, or distal urethra of either sex. In the normal prostate, specific immunocytochemical ER staining was confined to nuclei of the prostatic stroma and prostatic ductal epithelium. Specific staining intensity appeared to be higher in the periurethral region of the prostate than in the periphery. No specific staining was found in the acinar epithelium of the prostate. Based on overall staining intensity there appeared to be a higher concentration of ER in the urethra than in the prostate. Scatchard analysis of [3H]estradiol binding confirmed a similar ER content in the urethra of male and female dogs and a higher ER content in the prostatic urethra than in the prostate itself (P < 0.001). The location of ER in the normal canine prostate and prostatic urethra is consistent with the location of histological changes induced by estrogen administration, indicating that these immunoreactive ER probably represent biologically functional receptors.