Effect of Testosterone Replacement on Penile Erection in Castrated Rat

Lee, Hyun Bo; Sohn, Dong Wan; Im, Jae Gyun; Lee, Choong Bum; Kang, Sung Hak; Kim, Sae Woong; Cho, Yong Hyun; Yoon, Moon Soo

Abstract

PURPOSE
This study examined the changes in intracavernous pressure, expression of nitric oxide synthase(NOS), and content of penile smooth muscle in castrated rats and testosterone-supplied castrated rats.
MATERIALS AND METHODS
Sprague Dawley rats were used for this study and divided into control, castrated, and testosterone-supplied castrated groups. Castration was performed by bilateral orchietomy under general anesthesia, and testosterone propionate 3 mg/kg was injected subcutaneously daily for a week beginning 4 weeks after orchiectomy. Intracavernous pressure was measured by stimulating the cavernous nerve at 10 volts, 2.4 mA. Expression of NOS was measured by immunohistochemical staining for NADPH diaphorase, and content of penile smooth muscle was measured by H&E staining of the corpus cavernosum. The stained area-to-tissue ratio was calculated by computer scanning for each case.
RESULTS
Compared with the control group(3.45+/-0.25 ng/ml), the serum testosterone level of the castrated group (0.78+/-0.34 ng/ml) was lower. Serum testosterone level was restored in the testosterone-supplied castrated group. Compared with the(67.2+/-14.3 cmH2O) was decreased (p <0.05). There was no significant difference between the testosterone-supplied group(94.7+/-11.4 cmH2O) and control group, so intracavernosal pressure was restored by testosterone treatment. Immunohistochemical staining for NOS showed that NADPH diaphorase was stained as brown nerve fiber. Compared with the control group(37.5+/-2.8%), the NOS activity of the castrated group(7.5+/-2.1%) was significantly decreased(p <0.05). NOS activity was slightly increased in the testosterone-supplied group(47.5+/-2.4%) compared with the control group, but the difference was not statistically significant. Thus, testosterone treatment restored NOS activity after castration. By H&E staining, the content of penile smooth muscle was 76.5+/-2.8% in the control group, but significantly lower in the castrated group(46.2+/-3.4% p <0.05). Smooth muscle content was slightly decreased in the testosterone-supplied group(63.8+/-4.7%) compared with control group, but the difference was not statistically significant. Thus, smooth muscle content was restored by testosterone treatment after castration.
CONCLUSIONS
Decline of factors involved in erectile function can be restored by testosterone replacement after castration.