Inverse relation in the de novo arginase synthesis and nitric oxide production in murine and rat peritoneal macrophages in long-term cultures in vitro.

1. The de novo synthesis of arginase was much higher in murine than in rat peritoneal macrophages. This process was inhibited irreversibly by protein synthesis inhibitors and reversibly by glycolysis blockers. 2. Rat macrophages produce more nitric oxide (NO) than murine cells. NO production was inhibited by the inhibitors of protein synthesis or glycolysis. 3. The loading of macrophages by exogenous arginine for 24 hr in vitro resulted in the increase of arginase and nitrite in macrophages to different extents. 4. No great differences in lysozyme production was observed. 5. The proportion of arginine taken up and incorporated is contrasted in murine and rat macrophages.