Figure 2. Effects of IL-4 on LPS-induced inducible nitric oxide synthase (iNOS) and arginase activities in macrophages of young BALB/c mice (N = 6 per group). Naive and elicited peritoneal macrophages (PMΦ) and bone marrow-derived macrophages (BMMΦ) from young BALB/c mice were incubated with lipopolysaccharide (LPS; 1 µg/mL) in the presence or absence of interleukin-4 (IL-4; 1 or 10 IU/mL) for 48 h, at 37°C, in 5% CO₂. Cells of the control groups (C) were incubated in the absence of stimuli. Nitrite was measured in the culture supernatants using Griess reagent, and arginase activity was determined in cell lysates based on the amounts of urea produced from L-arginine. All studies were conducted in triplicate. Bars indicate the means ± SEM of nitrite (Panels A, B) and urea (Panels C, D) levels in three independent experiments. *P ≤ 0.05 (comparison was carried out by the Student t-test) and ^#P ≤ 0.05 (comparison was carried out by ANOVA followed by the Bonferroni post-test).