The rat phallus grows during sexual maturation as serum androgen concentrations rise to adult levels, and growth ceases when sexual maturity is attained despite the continued presence of adult serum androgen levels. This cessation of growth is correlated temporally with a diminution in the levels of androgen receptor, as detected by assays of ligand binding. To determine whether the change in androgen receptor content occurs in all cells in the tissue, immunohistochemical studies of the penile androgen receptor were performed in rats of different ages. In immature animals and animals castrated prepubertally, the androgen receptor is detected in virtually all cell types, including the corpus cavernosum penis, the small lateral cavernous bodies, the corpus cavernosum urethra, skin, urethra, and os penis. By contrast, in the mature rat penis minimal androgen receptor is evident within the corporal tissues and os, although immunoreactivity remains detectable in the penile skin and urethra. It is concluded that the cessation of androgen-mediated growth correlates with a decrease in androgen receptor levels in the body of the penis.
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