Intracavernosal injection of vascular endothelial growth factor induces nitric oxide synthase isoforms

Objective To identify genes that are affected by vascular endothelial growth factor (VEGF). as an intracavernosal injection with VEGF improved the recovery of erectile function in a rat model of arteriogenic impotence, specifically examining the three nitric oxide synthase (NOS) genes, nNOS, eNOS, and iNOS. Materials and methods Male rats had their pudendal arteries ligated or underwent a sham operation. They were then treated by an intracavernosal injection with 4 mug of VEGF in phosphate-buffered saline (PBS) or PBS alone. At 6 and 24 h after treatment electro-stimulation was applied to the cavernosal nerve and the intracorporal pressure measured. The erectile tissue was then harvested for RNA isolation and cryo-sectioning. The isolated RNA was used for microarray and reverse transcription-polymerase chain reaction (RT-PCR) analyses, and the tissue sections for immunohistochemical analysis. Results Microarray analysis detected nNOS, eNOS and iNOS at very low expression levels in PBS-treated rats: expression levels were higher for eNOS and iNOS in all VEGF-treated rats. These results were further confirmed by RT-PCR analysis. Immunohistochemical analysis identified the cavernosal endothelium and smooth muscle as the tissue types where eNOS and iNOS were up-regulated, respectively. Conclusions This is the first report of the induction of both eNOS and iNOS in the penis after intracavernosal VEGF. These events may help support a significant recovery of erectile function after interrupting the blood supply to the penis.