Inducible cytosolic enzyme activity for the production of nitrogen oxides from L-arginine in hepatocytes

The in vivo conditions needed for the induction of nitrogen oxide synthesis by hepatocytes were determined. Hepatocytes obtained from rats injected with killed Corynebacterium parvum spontaneously produced NO₂^-+NO₃^- in culture and were found to contain cytosolic enzyme activity for nitrogen oxide synthesis. The enzyme activity required both L-arginine and NADPH, and was not found in hepatocytes obtained from normal rats or rats injected with lipopoly-saccharide (LPS) alone. In contrast, nonparenchymal cells were stimulated to synthesize NO₂^-+NO₃^- by LPS. These results show the presence of inducible cytosolic enzyme activity for nitrogen oxide synthesis in hepatocytes, which is distinct from nonparenchymal cell NO^- synthesis.