Effects of insulin-like growth factor-1 on the relaxation responses of the cavernous smooth muscle from aged rats

Abstract

Objective. The aim of this study was determine whether intracavernosal injection (ICI) of insulin-like growth factor-1 (IGF-1) protein can improve corpus cavernosal smooth muscle relaxation in aging rats. Materials and methods. Ten young (4-month-old) and 30 old (24-month-old) Sprague–Dawley male rats were enrolled in the study. The old rats were divided into three groups: vehicle-only (n = 10), IGF-1 1 µg/kg (n = 10) and IGF-1 10 µg/kg treatment groups (n = 10). After 4 weeks of single IGF-1 injection treatment, strips of corporal tissue were precontracted with phenylephrine, and dose–response curves were generated to evaluate endothelial-dependent [acetylcholine (ACh)], endothelial-independent [sodium nitroprusside (SNP)] and electrical field stimulation (EFS) vasoreactivity. The changes in percentage of cavernosal smooth muscle and the concentration of nitric oxide (NO) in penile tissue were also evaluated. Results. After IGF-1 treatment, the vasoreactivity was significantly improved in both the 1 µg/kg and the 10 µg/kg treatment groups compared with the vehicle-only group at 4 weeks in response to ACh, SNP and EFS (all p < 0.05). The percentage of cavernosal smooth muscle was increased in the IGF-1 treatment groups. The NO concentrations were increased after IGF-1 treatment. Conclusions. These data demonstrate that ICI of IGF-1 can improve vasoreactivity via endothelium-dependent and endothelial-independent mechanisms in the corpus cavernosum of the aging rat.

Key Words:

• Cavernosal smooth muscle
• insulin-like growth factor-1
• intracavernosal injection
• rats
• vasoreactivity

Acknowledgements

This work was supported by the National Natural Science Foundation of China [81270855, 30801147], the Science and Technology Planning Program of Guangzhou [2014J4100041], the Medicine Science Study Foundation of Guangdong Province [A2012016, A2008033], the Science Study project of Guangdong General Hospital [Y012012012], the Science and Technology Planning Project of Guangdong Province [2011B031800092] and the Fundamental Research Funds for the Central Universities of China [09ykpy16].

Declaration of interest: The authors declare that they have no conflicts of interest.