Adenosine (ado) enhances arginase activity and TIMP-1 production by IL-13-activated macrophages. A) Adenosine up-regulates IL-13-stimulated arginase activity in RAW 264.7 macrophages. RAW 264.7 macrophages were challenged with 5 ng/ml IL-13 and treated with 100 μM adenosine for 8 h, and then arginase activity was measured from the cell lysate. B) Adenosine augments IL-13-evoked arginase-1 mRNA accumulation. RAW 264.7 macrophages were challenged with 5 ng/ml IL-13 and treated with 100 μM adenosine for 4 h, and mRNA abundance was measured using real-time PCR. C) Adenosine enhances IL-13-induced TIMP-1 release by peritoneal macrophages. Peritoneal macrophages were stimulated with IL-13 and treated with adenosine for 24 h, and then TIMP-1 levels were measured from the supernatants using ELISA. Results are shown as means ± se and are representative of ≥3 experiments; n = 6/experiment. **P < 0.01, ***P < 0.001 vs. control (con); #P < 0.05, ##P < 0.01 vs. IL-13.