Background: In response to injury, muscle catabolism can be
extensive, and in theory, the wound consumes amino acids to support healing.
The purpose of this study is to assess a technique by which in vivo
protein kinetics of muscle, wound, and normal skin can be quantified in
burn-injured patients. Methods: Study protocol consisting of infusion
of d5 phenylalanine; biopsies of skeletal muscle, skin, and
donor-site wound on the leg; quantification of blood flow to total leg, wound,
and skin; and sequential blood sampling from the femoral artery and vein.
Five-compartment modeling was used to quantify the rates of protein synthesis,
breakdown, and phenylalanine transport between muscle, wound, and skin.
Results: The study results demonstrated a net release of
phenylalanine from muscle yet a net consumption of phenylalanine by the wound.
Compared with skin, the wound had a substantially increased rate of protein
synthesis and a reduced rate of protein breakdown (p < .01).
Transport rates into and out of muscle were significantly higher than those
for wound (p < .01). Conclusions: This novel methodology
enables in vivo quantification of the integrated response of muscle,
wound, and skin protein/amino acid metabolism and confirms the long-held
theory of a net catabolism of muscle and a net anabolism of wound protein in
patients after injury. This methodology can be used to assess the metabolic
impact of such measures as nutrition, pharmacologic agents, and surgical
procedures.
It has long been theorized that in hypermetabolic patients, amino acids released by muscle protein catabolism are consumed by the wound. This study confirms this assumption by quantifying in vivo the integrated response of muscle, wound, and skin protein/amino acid metabolism in severe burn patients.
