OBJECTIVETo investigate the best dose and the long-term effect of the human insulin-like growth factor-1 (hIGF-1) gene injection into the penis of aged rats.

METHODSIncluded in this study were 10 young (4 months old) and 40 aged (24 months old) Sprague-Dawley male rats, the latter equally divided into a PBS control and a 10 microg, a 100 microg and a 1 000 microg hIGF-1 injection group. Electrical stimulation was conducted 4 and 8 weeks after hIGF-1 injection into the penile corpus cavernous of the rats to detect the intracavernous pressure (ICP) and mean arterial pressure (MAP). Dose - and time -associated therapeutic results were analyzed and the mRNA expression of hIGF-1 determined by RT - PCR.

RESULTSICP, MAP and total ICP were significant decreased by electrical stimulation in the aged rats as compared with the young ones (P < 0.05), statistically increased in the three hIGF-1 dose groups in comparison with the PBS controls (P < 0.05), and showed no obvious difference between the young rats and the latter two dose groups at 4 and 8 weeks. Although less obvious effect was achieved in the 10 microg group than in the young rats, the therapeutic result was still of significance. The mRNA expression of the hIGF-1 gene was confirmed in all the hIGF-1 treated rats.

CONCLUSIONThe hIGF-1 therapy can improve erectile function in aged rats, 100 microg suffices for effective erection and the effect may last at least 8 weeks for a single dose.