Iron released by IFN-γ/LPS-activated J774 macrophages. Cells were stimulated overnight with IFN-γ (50 U/mL), LPS (10 ng/mL), and/or NMMA (500 μmol/L), pulsed for 4 hours with 50 μg/mL⁵⁹Fe-Tf, and then incubated 2 more hours in the presence of unlabeled Fe-Tf. Nitrite production was assayed in the culture medium by the Griess reaction. Results shown are representative of 3 separate experiments. Values are given as the mean ± SE of triplicate cultures.