Stimulation of arginine consumption and asparagine production in LPS-activated macrophages

Changes in amino acid utilization during lipopolysaccharide (LPS)-induced activation of mouse macrophage-like cells Raw264.7 were investigated. Amino acids in the medium and cell fractions were extracted by 5% trichloroacetic acid and quantitated by amino acid analyzer. Glutamine was utilized by cells at the highest rate, followed by serine and arginine, a precursor of nitric oxide (NO). When Raw264.7 cells were incubated with 10 or 100 ng/mL LPS, the consumption of arginine and the production of citrulline, nitric oxide (NO) and asparagine were significantly increased. The intracellular amino acid concentration was not significantly changed. These data suggest that arginine consumption and asparagine production might be possible markers of macrophage activation.