EFFECTS OF SYMPATHETIC DENERVATION AND OXYGEN-FREE RADICALS ON NEOVASCULARIZATION IN SKIN FLAPS

An island skin flap, with its sole blood supply based on the inferior epigastric vessels, in Sprague-Dawley rats (female, 220 to 250 gm) was used as a model for the investigation of neovascularization. Flap sur vival after pedicle ligation was considered an indicator of neovascula rization. Vascular pedicles were ligated on days 2 to 5 after flap ele vation, and the time course of neovascularization in the innervated an d denervated flaps was determined by measurements of survival on day 7 after pedicle ligation (on days 9 to 12 postoperatively). Neovascular ization sufficient to maintain viability was established at 4 and 5 da ys after flap elevation in the innervated and denervated flaps, respec tively. The effects of various scavengers of oxygen free radicals on n eovascularization were evaluated in the innervated and denervated flap s. The pedicles were ligated 3 days after flap elevation. Flap surviva l was assessed on day 7 after pedicle ligation (on day 10 postoperativ ely.) Treatment with a single dose of deferoxamine (50 mg/kg) increase d the viability from 48 to 69 percent of flap area in the denervated f laps (p < 0.01) but produced little effect on viability in the innerva ted flaps. In the denervated flaps, treatments with a single dose of s uperoxide dismutase, intravenously and intraarterially, also substanti ally increased the survival rates from 29 to 86 percent (marginally si gnificant) and 100 percent (p < 0.05), respectively. Allopurinol impro ved the survival from 43 to 88 percent; the difference was not statist ically significant. The results suggest that denervation resulted in a delay of neovascularization and that severe sympathetic denervation c ontributes to the production of Oxygen free radicals, which may exert their inhibitory effects on neovascularization.