Arginine and ornithine kinetics in severely burned patients: increased rate of arginine disposal |
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Authors: | Yu Y M Ryan C M Castillo L Lu X M Beaumier L Tompkins R G Young V R |
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Institution: | Shriners Burns Hospital and Trauma Service, Massachusetts General Hospital, Boston, MA 02114, USA. |
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Abstract: | Arginine serves multiple roles in the pathophysiological response to burn injury. Our previous studies in burn patients demonstrated a limited net rate of arginine de novo synthesis despite a significantly increased arginine turnover (flux), suggesting that this amino acid is a conditionally indispensable amino acid after major burns. This study used 15N2-guanidino-5,5-2H2]arginine and 5-13C]ornithine as tracers to assess the rate of arginine disposal via its conversion to and subsequent oxidation of ornithine; 5,5-2H2]proline and 5,5,5-2H3]leucine were also used to assess proline and protein kinetics. Nine severely burned patients were studied during a protein-free fast ("basal" or fast) and total parenteral nutrition (TPN) feedings. Compared with values from healthy volunteers, burn injury significantly increased 1) fluxes of arginine, ornithine, leucine, and proline; 2) arginine-to-ornithine conversion; 3) ornithine oxidation; and 4) arginine oxidation. TPN increased arginine-to-ornithine conversion and proportionally increased irreversible arginine oxidation. The elevated arginine oxidation, with limited net de novo synthesis from its immediate precursors, further implies that arginine is a conditionally indispensable amino acid in severely burned patients receiving TPN. |
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