Purpose : Androgen plays an important role during penile development and is essential
for a normal libido in the male, but its role in the regulation of the androgen receptor
and maintenance of erectile response has been controversial. We investigated the effect
of androgen on apoptosis, proliferation of the penile erectile tissue and androgen receptor
after castration and temporary androgen replacement.
Materials and Methods : Male adult Sprague Dawley rats were divided into three
groups; sham-operation, castration, and androgen replacement after castration.
Androgens(testosterone, DHT) were administrated for 7 days at week 1, 2, 3, and 4
after castration. The weight of whole body and corpus cavernosum and serum
testosterone concentration were measured. Androgen receptor expression, percentage of
proliferating cells incorporating Ki-67(proliferative index) and percentage of apoptotic
cells assessed by morphological analysis(apoptotic index, TUNEL) were analyzed in the
penile erectile tissue.
Results : Castration induced a significant decrease in serum testosterone concentration
from day 1 and a progressive decrease in the corpus cavernosal weight from day 14.
Androgen receptor expression decreased after androgen depletion and was restored with
androgen replacement. The proliferative and apoptotic index varied as follows after
castration and androgen replacement: a significant increase was noted for apoptotic index
with a decrease in the proliferative index and androgen receptor expression after
castration. Replacement of testosterone propionate and DHT after castration decreased
the apoptotic index with an increase in the proliferative index and the expression rate of
androgen receptor.
Conclusions : The penile erectile tissue of the adult rat was affected by the androgen
milieu via the androgen receptor as seen by either cellular apoptosis or proliferation.
Therefore, androgens such as testosterone and DHT play a direct role in the erectile
function of the rat at the level of the penile erectile tissue.