Effect of supplemental ornithine on wound healing

BACKGROUND: Supplemental arginine has been shown to enhance wound healing, in particular collagen synthesis. Ornithine is the main metabolite of arginine in the urea cycle and shares many of the biopharmacologic effects of arginine. The present study examines the effect of ornithine supplementation on wound healing and attempts to describe its possible mechanism. METHODS: Wild type (WT) and iNOS knockout (KO) mice were randomized to receive either normal chow and tap water or chow and water each supplemented with 0.5% ornithine (w/w). All animals underwent a midline dorsal skin incision with implantation of polyvinyl alcohol sponges into subcutaneous pockets. On postoperative day 14 the animals were sacrificed. The dorsal wound was harvested for breaking strength determination while the wound sponges were assayed for hydroxyproline content, total wound fluid amino acid, and nitrite/nitrate (NOx) concentration. RESULTS: Dietary ornithine supplementation enhanced wound breaking strength and collagen deposition in both WT and KO mice. This was accompanied by increased wound fluid proline and ornithine levels but not arginine, citrulline, or NOx levels. CONCLUSIONS: The results from this study demonstrate that ornithine supplementation enhances wound healing in both WT and KO mice. This suggests that ornithine's effect on wound healing is independent of the iNOS pathway.