Intracavernosal Injection of Insulin Like Growth Factor-1 Improves Erectile Function in Aging Rat

Ahn, Kyu Youn; Park, Kwangsung; Oh, Kyung Jin; Kim, Min Kyung; Lee, Song Eun; Lee, Young Ik; Ryu, Soo Bang

Abstract

PURPOSE
Insulin like growth factor-1 (IGF-1) is known to promote the proliferation and migration of penile cavernous smooth muscle cells in rat. The purpose of this study was to investigate whether IGF-1 could restore erectile function in the aging rat.
MATERIALS AND METHODS
Male Sprague-Dawley rats were divided into two groups: young (4~5 months; n=10) and old (24 months; n=30). The old group was further divided into vehicle only (phosphate buffered saline plus 0.1% bovine serum albumin; n=10) and IGF-1 treatment (100 microgram; n=20) groups. Half of the IGF-1 dose (50 microgram) was injected on the first day, and half was injected on the third day. After 2 and 4 weeks of treatment, erectile function was evaluated by hemodynamic study, and corpus cavernosal histology was examined by histomorphometric analysis.
RESULTS
The ratio of peak intracavernosal pressure to systemic arterial blood pressure was significantly lower in the vehicle-only old rats (63.1 8.5%) compared to young rats (74.6 3.2%) (p=0.016). However, after 4 weeks of treatment, the ratio was significantly increased in the IGF-1 treatment group (77.2 7.0%) compared to the vehicle-only group (p<0.05). The percentage of smooth muscle was significantly lower in the vehicle-only old rats (12.8 2.2%) compared to young rats (17.8 3.7%) (p=0.047), whereas, it was significantly increased in the IGF-1 treatment group (19.4 3.3%) compared to the vehicle-only group (p=0.014).
CONCLUSIONS
Intracavernosal injection of IGF-1 in the old rats resulted in increased intracavernosal pressure and higher percentage of cavernosal smooth muscle. These results suggest that intracavernosal injection of IGF-1 appears to restore smooth muscle integrity and improve erectile function in aged rats.