The effects of testosterone replacement on penile structure and erectile function in castrated adult male rats

Abstract

Objectives: To evaluate the effects of testosterone on penile structure and erectile function in adult male rats. Patients and Methods: Whole subjects were divided into two groups by observation period (group I (n=30), 12 weeks; group II (n=30), 20 weeks). Each group had three difference subgroups (10 rats each). Sham-operated control, surgical castration group and testosterone replacement for 4 week after 8 weeks of castration period. Group II also had a same kind of subgroup. Control, castration, and last subgroup had more longer castration period (16wks) and testosterone replacement at 4weeks before sacrifice. Erectile function was assessed by measuring intracavernosal pressure in response to cavernous nerve stimulation, and the expression of nNOS protein was determined by Western blot analysis. Serum testosterone values were measured in each animal by radioimmunoassay Results: Serum testosterone levels and cavernousal smooth muscle contents and nNOS activity decreased significantly in castrated animals, whereas Testosterone undecanoate injection normalized the serum levels of testosterone and others. Total Intracavernosal pressure / mean arterial pressure was significantly decreased in untreated castrated rats. compared with intact controls (28.3 +- 3.5 and 78.9+-8.2, respectively). Erectile function was normalized in 4 weeks of androgen-replaced rats. The expression of nNOS was decreased in the corpus cavernosum of castrated animals compared with controls, whereas androgen replacement normalized the expression of nNOS. These results were consistently observed despite the period of androgen deprivation. Conclusions: These data suggest that androgen regulates the expression of nNOS in rat penile corpus cavernosum and confirms the importance of androgens in the maintenance of erectile function. Howerver, irreversible structural and erectile functional changes are not found during study period.