Transport of L-arginine and nitrite production were examined in the murine macrophage cell line J774. Bacterial lipopolysaccharide (LPS) induced a dose-and time-dependent stimulation of nitrite production, which was further increased in the presence of interferon-y. Nitrite synthesis was absolutely dependent on extracellular L-arginine and inhibited in the presence of L-lysine or L-ornithine. In unactivated J774 cells L-arginine transport was saturable, with an apparent Km of 0. 14 + 0.04 mm and Vma. of 15 + 2 nmol/h per 106 cells. LPS (1 ,ug/ml) induced a time-dependent stimulation of L-arginine transport, and after 24 h the Vm.. increased to 34 + 2 nmol/h per 106 cells. These findings indicate that activation of J774 cells with LPS produces an increase in both L-arginine transport and nitrite synthesis. The elevated rate of L-arginine transport in activated J774 cells may provide a mechanism for sustained substrate supply during enhanced utilization of L-arginine for the generation of NO.
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