Effect of Septic Shock on Nitrate, Free Amino Acids, and Urea in Murine Plasma and Urine

Objectives: Concentration changes of free amino acids, urea, and nitrate in plasma and urine were studied for the murine model of septic shock. Methods: After administration of a bolus dose of bacterial lipopolysaccharide (LPS), concentrations of amino acids and urea in plasma, and urea and nitrate in urine were determined. Results: For individual amino acids four different trends were observed: (1) no change (e.g., taurine, histidine, phenylalanine, hydroxproline); (2) continuous increase (e.g., aspartate and glutamate); (3) continuous decrease (e.g., threonine, serine, asparagine, proline, methionine, tyrosine); and (4) decrease during the first 4 hours, but return to normal at 8 hours after the LPS treatment (e.g., all the other amino acids). The ratio of phenylalanine to tyrosine was increased to about 2×. In plasma, urea concentration was increased about 3×, but in urine it decreased about 4×. Nitrate levels were increased 3× in urine. Conclusion: These early changes in the concentrations of amino acids as well as in the urea and nitrate may be useful as sensitive markers for the early and rapid diagnosis of septic shock.