Figure 1

B16F1 melanoma cell-induced iNOS expression, NO production and nitrotyrosine formation in the mouse liver. (A): Induction of hepatic iNOS expression (0–24 h) in various strains of C57BL/6 mice injected with B16F1 melanoma cells or polystyrene (P.S.) beads. iNOS was detected by immunofluorescent double-labeling using rabbit anti-mouse iNOS as the primary and Cy™3-conjugated goat anti-rabbit IgG as secondary antibodies. Data represent the mean ± SE of iNOS positive cells in 25 fields of each mouse liver in the group (n = 5 mice/group, at 200 × magnifications). WT: Wild-type. KO: Knockout; (B): iNOS expression (orange, arrows) in sinusoidal lining cells and hepatocytes of a wild-type mouse liver at 24 h after injection of melanoma cells (green); (C): iNOS detection negative control in a normal wild-type liver without cell injection. (D): Liver sample excised immediately after B16F1 cell injection (arrows, 0 h, 100 ×); (E): NO signal detected in the 0 h liver sample using EPR spectroscopy; (F): Nitrotyrosine (NT, red, arrows) detection in the same 0 h liver, by double-labeling immunohistochemistry using mouse anti-nitrotyrosine primary antibody, along the sinusoidal wall adjacent and inside the arresting tumor cells. (G): A negative control of NT detection in a wild-type mouse liver without tumor cell injection. Scale bars displayed in μm.