The Flow Phase of Wound Metabolism Is Characterized by Stimulated Protein Synthesis Rather Than Cell Proliferation

Background: Healing of a skin wound requires net protein deposition to repair the tissue defect and new epidermal cells to cover the wound. However, the true course of changes in rates of cell proliferation and protein deposition following skin injury has not been previously determined. This experiment was to measure DNA fractional synthetic rate (FSR), reflecting cell division, and protein FSR and fractional breakdown rate (FBR) in skin wound at three times after injury. Materials and methods: The experiment consisted of a surgery and a tracer infusion on separate days. During the surgery (day 0), a donor wound was created and indwelling catheters were inserted into the carotid artery and jugular vein under general anesthesia. On day 1, day 3, or day 7, stable isotope tracer infusion was performed in conscious rabbits to determine DNA FSR and protein FSR and FBR in the wound. Results: Protein FSR and FBR in the day 7 wound were 20.5 ± 8.4 and 12.6 ± 4.7%/day, respectively, which were greater (P < 0.01-0.05) than the corresponding values in the day 1 and day 3 wounds. Net protein deposition (FSR-FBR) in day 7 wound (7.9 ± 6.0%/day) was greater (P < 0.05) than in day 3 wound (0.8 ± 2.4%/day). DNA FSRs were 1.94 ± 0.58, 2.43 ± 0.96, 2.86 ± 0.90%/day in the day 1, day 3 and day 7 wounds, respectively (P = 0.2). Conclusions: The flow phase in the wound is characterized by increased protein synthesis rather than cell proliferation; net protein deposition in the wound is a major cause of protein requirements in severe burns.