Background: The aim of this study was to clarify the histological, ultrastructuraland biomechanical effects of pentoxifylline (PTX) on the survival of random skin flaps (RSFs) in rats.Material/Methods: Thirty male rats were randomly divided into experimental, sham and control groups.The experimental group received PTX 20 mg/kg/day, and the sham group received saline. A 20x70-mm RSFwas made 30 days after the commencement of treatment for the three groups. PTX and saline were continuedpostoperatively for 7 days in the experimental and sham groups, respectively. On the seventh postoperativeday, the surviving parts of the flaps were determined and examined through light and transmission electronmicroscopes. The wounds (incisions) on the margins of the flaps were evaluated histologically and biomechanically.Results: Analysis of variance showed that, in the experimental group, the mean of the surviving partsof the RSFs, fibroblast proliferation, collagen organization and granulation tissue of the wounds wassignificantly higher than in the sham and control groups (P=0.007, P=0.001, P=0.041, P=0.000, respectively).There were swollen mitochondria in the endothelium of the blood vessels of the surviving flap parts inthe control and sham groups, whereas in the experimental group the mitochondria were normal. Conclusions:Thirty days of pretreatment of RSFs with PTX significantly increased the survival of the flaps. PTX appearedto have healed wounds and reversed ultrastructural changes resulting from hypoxia in the blood vesselendothelium of the flaps.

Keywords: Blood Vessels - ultrastructure, Biomechanical Phenomena, Endothelium, Vascular - ultrastructure, Graft Survival - drug effects, Hematologic Agents - administration & dosage, Microscopy, Electron, Transmission, Mitochondrial Swelling, Pentoxifylline - administration & dosage, Skin - ultrastructure, Surgical Flaps