The estrogen receptor expression in the male rabbit urethra and prostate following castration

The influence of castration on estrogen receptor (ER) expression in the male rabbit prostate and urethra, was investigated immunohistochemically and biochemically in 18 mature male, rabbits 14 days after bilateral orchiectomy, and in 15 controls. Immunohistochemical scores of ER were increased significantly in the prostatic stroma and the urethral submucosa (p < 0.05 Mann-Whitney), while the increase in the urothelium was not significant. Biochemically, the ER content was 87.4 +/- 42.6 f mol/mg protein in the normal prostate, and 190.0 +/- 28.0 f mol/mg protein following castration. The corresponding values for the posterior urethra were 228.3 +/- 43.2 f mol/mg protein and 354.9 +/- 60.1 f mol/mg protein. In both cases the increase was not significant. We conclude, that ERs in the prostate and the urethra of the male rabbit can be modified by hormonal manipulation. ERs may therefore be functionally active and not rudimentary.