The effect of mirodenafil on the penile erection and corpus cavernosum in the rat model of cavernosal nerve injury

Abstract

Impotence is one of the common complications after the radical prostatectomy. One of the main reasons of this complication is due to the dysfunction of the veins in corpus cavernosum. Recent studies have shown that the erectile function is improved after the long-term therapy of phosphodiesterase type 5 inhibitor among patients with post-prostatectomy erectile dysfunction. In this study, we evaluated the effects of mirodenafil on the penile erection and corpus cavernosum tissues in the rat model of cavernosal nerve injury. Rats were divided into four groups: (1) control group, (2) bilateral cavernosal nerve injury group, (3) mirodenafil 10 mg therapy group after the nerve injury and (4) mirodenafil 20 mg therapy group after the nerve injury. After we identified the nerve from the pelvic nerve complex on the lateral side of the prostate, the rats in the control group were sutured without causing any nerve injury and in other groups we damaged the nerve by compressing it with a vessel clamp. Then, 10 and 20 mg kg(-1) of mirodenafil were orally administered to two experimental groups. After 8 weeks, the intracavernosal pressure (ICP) was recorded. The immunohistochemical staining and western blot were performed, and the effect of mirodenafil on the expression of cyclic guanosine monophosphate (cGMP) was evaluated through enzyme-linked immunosorbent assay. The ICP of nerve-injured group was decreased compared with the control group; however, the ICP of the mirodenafil-administered groups was improved compared with the nerve-injured group. The Masson's trichrome staining confirmed that the smooth muscle (SM) component was increased in the mirodenafil-administered groups. The nitric oxide synthase expression and cGMP of mirodenafil-administered groups was increased compared with the nerve-injured group. Long-term therapy of mirodenafil may improve the erectile function after the radical prostatectomy by preserving the SM content and inhibiting the fibrosis of the corpus cavernosum.

Figure 1

Masson's trichrome staining for collagen (blue) and smooth muscle ( × 100). Control group, normal group; BCNX group, cavernosal nerve injury group; M10 group, mirodenafil 10 mg kg⁻¹ administered group intake after cavernosal nerve injury; M20 group, mirodenafil 20 mg kg⁻¹ administered group after cavernosal nerve injury.

Figure 2

The expression of NOS at 8 weeks after cavernosal nerve injury.

Figure 3

The expression of NOS at 8 weeks after cavernosal nerve injury. ^*Significantly different (P<0.05) from the BCNX group. ^**Significantly different (P<0.05) from the BCNX group.

Figure 4

The effect of mirodenafil on cGMP at 8 weeks after cavernosal nerve injury. ^*Significantly increased (P<0.05) compared with BCNX group. ^**Significantly increased (P<0.05) compared with BCNX group.