Figure 7. Nitric oxide production.

A. Extracellular nitrite (NO₂ ⁻) content as a function of parasitemia for trophozoite-infected RBCs (t-RBCs, 0–4% parasitemia) incubated for 24 hs in supplemented RPMI medium. Cells were cultured in an atmosphere of 90% N₂/5% O₂/5% CO₂ at 37°C containing 1.15 mM L-arginine. B. Microphotographies from DAF-2 diacetate loaded RBCs under bright light (left) and fluorescence illumination (right). Green arrows show trophozoite-infected cells, and red arrows indicate noninfected RBCs. Total magnification 1000X. C. DAF-2 diacetate fluorescence intensities of cell suspensions as a function of time, determined by fluorometry. Experiments were run using h- and t94-RBCs. Before the experiments, cells were pre-incubated 3 hs in the absence and presence of 2 mM L-NAME. D. NO production was estimated from the slopes of linear fits to data shown in C. Results (au/min) are means ± SEM with N = 3, n = 6–12. Significant differences are indicated (*, p<0,05, **, p<0,01).