RESUMEN
Abstract Purpose: To investigate the prophylactic and therapeutical effects of sildenafil in a model of acute radiation proctitis (ARP). Methods: All experimental procedures of this study was examined by histopathological, immunohistochemical and transmission electron microscopic analysis. Results: Our histopathological evaluations indicated significant increases in lesion severity, cryptic apsis, cryptitis, cryptic distortion, reactive atypia and infiltration depth of the control (proctitis) group. While the prophylaxis group and the treatment group had significantly lower scores. High-dose group showed similar results as prophylaxis group. Histopathological findings of the prophylaxis group was more significant than the treatment group. Immunoreactivities of IL-1β, FGF-2, TNF- α and HIF-1α increased in the control group especially in the epithelial and cryptic regions. On the contrary, sildenafil application caused significant decreases of inflammatory markers in all treatment groups, specifically better results in the prophylaxis group. Conclusion: The sildenafil has anti-inflammatory effects on ARP, as well as protective effects against ARP and the protective effect of sildenafil surpasses its therapeutic effect histopathologically.