Plasma and heart tissue were collected from BALB/c mice not infected (NI) or infected with a lethal dose of T. cruzi (I) and sacrificed at 21 d.p.i. (A) Parasitemia, as determined by direct counting under the optical microscope. (B) Western blot analysis of heart tissue extracts using antibodies against iNOS and Arg-1; Ponceau staining of the membrane is shown as a protein loading control. (C) Ornithine, urea, proline, citrulline, SDMA+ADMA, and L-arginine levels were determined in plasma and relative levels expressed as ScaledImpData as described in the Materials and Methods; the L-arginine/SDMA+ADMA ratio is also shown. (D) Ornithine, urea, proline, citrulline, ADMA, putrescine, and L-arginine levels were determined in heart tissue extracts; the L-arginine/ADMA ratio is also shown. Results from a single experiment are shown in box and whisker graphs; statistical analysis was performed using Student’s t-test (n = 6 mice per experimental group; *p<0.05; **p<0.005; ***p<0.001).