<p>The mice were infected with 100 blood trypomastigotes of the Colombian <i>T. cruzi</i> strain and analyzed at 40 dpi. The presence of iNOS/NOS2<sup>+</sup> cells, parasite nests, inflammatory cells and Cx43 in the myocardium was immunohistochemically detected, NO concentration was evaluated by a Griess-based method and CK-MB activity levels in the serum was biochemically determined. (<b>A</b>) Increased NO levels in serum of <i>T. cruzi</i>-infected C57BL/6 mice in comparison with noninfected controls (NI). (<b>B</b>) Photomicrograph of iNOS/NOS2<sup>+</sup> cells in the cardiac tissue of infected C57BL/6 mice and quantification of iNOS/NOS2<sup>+</sup> cells in the cardiac tissue of infected C57BL/6 mice in comparison with noninfected controls. (<b>C</b>) Photomicrographs and quantification of parasite nests showing increased heart parasitism in <i>Nos2</i><sup>−/−</sup> compared with <i>T. cruzi</i>-infected C57BL/6 mice. (<b>D</b>) Similar number of inflammatory cells in the heart tissue of C57BL/6 and <i>Nos2</i><sup>−/− </sup><i>T. cruzi</i>-infected mice. (<b>E</b>) CK-MB activity levels in the serum of noninfected and <i>T. cruzi</i>-infected mice revealing increased CK-MB activity in <i>T. cruzi</i>-infected mice when compared with noninfected controls. Decreased CK-MB activity in the serum of <i>Nos2</i><sup>−/−</sup> compared with C57BL/6 <i>T. cruzi</i>-infected mice. (<b>F</b>) Preserved expression of Cx43 in the heart tissue of <i>Nos2</i><sup>−/−</sup> compared with C57BL/6 infected mice. Analysis at 40 dpi of 3–5 noninfected and 5–8 infected mice/group. * <i>p</i><0.05 and ** <i>p</i><0.01. Bar = 100 µm (<b>C</b>). Bar = 50 µm (<b>F</b>).</p
