The effects of androgen administration on phallic androgen receptor expression

Whether androgens down regulate the androgen receptor during penile development is controversial. We investigated the effects of androgens on penile androgen receptor expression.

We injected prepubertal hypogonadotropic hypogonadal microphallic rats with testosterone or dihydrotestosterone. Specimens were obtained at 3 (prepuberty), 9 (puberty to early postpuberty) and 12 weeks (late postpuberty). At necropsy we compared penile size and androgen receptor expression of these animals to those of age matched nontreated hypogonadotropic hypogonadal and normal controls.

At age 3 weeks prepubertal androgens up regulated androgen receptor expression and significantly increased penile size compared to normal and untreated hypogonadotropic hypogonadal controls. By 9 weeks the normal down regulation of androgen receptor that occurs with maturation was present. Prepubertal androgens failed to accelerate or exaggerate the normal maturational loss of the androgen receptor. At 9 weeks penile size of normal controls and prepubertal androgen treated animals was identical. Interestingly despite down regulation of the penile androgen receptor, normal animals continued to have increases in penile size between 9 and 12 weeks, while the prepubertal androgen treated animals had no penile growth.

Prepubertal androgen administration in hypogonadotropic hypogonadal animals resulted in diminutive penises in adulthood. However, the decrease in penile size was not associated with an accelerated or exaggerated down regulation of the androgen receptor. This finding coupled with continued growth of the normal control penises after androgen receptor down regulation suggests that cessation of penile growth may not be solely related to down regulation of the penile androgen receptor.