The expression of receptors for estrogen and epithelial growth factor in the male rabbit prostate and prostatic urethra following castration.

In the lower urinary tract of the male rabbit, estrogen receptors (ERs) are restricted to the urethra and the prostatic stroma. At present, the function of ERs in these tissues is not known. Epithelial growth factor (EGF) stimulates proliferation of epidermal and epithelial tissues, and several animal studies have indicated that EGF is regulated by estrogen. On this background, we have studied the effect of castration on the expression of ERs and EGF receptors in the rabbit prostatic urethra and prostate. Twelve male rabbits were studied fourteen days after castration, and eight normal rabbits were included as controls. In the control group, ERs were found in the urothelial lining and lamina propria of the prostatic urethra, and in the prostatic stroma. EGF receptors were demonstrated in the epithelial lining of the prostatic urethra and the glandular epithelium of the prostate. Following castration, the expression of ERs, assessed as the increase in the number of positively stained specimens, increased significantly in the lamina propria of the prostatic urethra and the prostatic stroma. EGF receptor expression increased significantly in the epithelial lining of the prostatic urethra. In the prostate, the increase was not significant. The results give no support to the view that ERs play role in the regulation of EGF receptors in the rabbit prostatic urethra nor the prostate.