<p> <b>A</b>) Arginase activity in macrophages isolated by adherence from single-cell suspensions from the spleens of control hamsters (0 days post-infection) and hamsters infected with <i>L. donovani</i> for 7, 14, 21, 42, and 56 days. The mean and SD (error bars) of the arginase activity in 100,000 cells, determined by assay of urea production, is shown from a single experiment that is representative of 2 independent experiments. <b>B</b>) Log<sub>10</sub> ratio of host arg1 to NOS2 mRNA in splenic macrophages of 4-week <i>L. donovani</i> infected mice and hamsters. The mRNA expression was determined by real time RT-PCR in groups of 5 animals and used to calculate the log ratios, shown as the mean and SD (error bars) from a single experiment that is representative of 2 independent experiments. The ratios were determined from the following raw data: Arg1 mRNA fold-increase with reference to the BHK cell calibrator (mean ± SD): uninfected mice, 5.7±5.9; uninfected hamster, 3,367±2,858, infected mice, 8.5±10; infected hamster, 131,984±56,407; iNOS mRNA fold-increase with reference to BHK cell calibrator (mean ± SD): uninfected mice, 133.34±182.4; uninfected hamster, 1.03±0.3, infected mice, 2,984±4,535; infected hamster, 19.56±10.87). <b>C</b>) Arginase activity in peritoneal macrophages isolated from mice and hamsters that were uninfected (open bars) or infected in vitro with <i>L. donovani</i> for 48 hrs (filled bars). The mean and SD (error bars) of the arginase activity, determined by assay of urea production, is shown from a single experiment that is representative of 2 independent experiments. <b>D</b>) Arginase activity in hamster peritoneal macrophages that were uninfected (Un) or infected in vitro with <i>L. donovani</i> (1∶5 macrophage:parasite ratio). Parasites were either unopsonized (None), opsonized with normal fresh complement-containing hamster serum (Comp), or opsonized with freeze-thawed hamster serum containing anti-Leishmania antibody (Ab). The mean and standard deviation (error bars) of the arginase activity in 200,000 cells of 6 different samples determined by assay of urea production, is shown from a single experiment that is representative of 2 experiments. Statistical comparisons are made to the control group. <b>E</b>) Expression of hamster arginase mRNA in hamster peritoneal macrophages that were uninfected (Un) or infected in vitro with <i>L. donovani</i> stationary-phase promastigotes for 24 hrs (Inf). The mean and SEM (error bars) of the fold-increase of arg1 mRNA relative to BHK cells, determined by real time RT-PCR in groups of 6 samples per experiment, is shown as data pooled from 4 independent experiments. <b>F</b>) The concentration of polyamines in uninfected (open bars) and 48-hour in vitro infected hamster peritoneal macrophages (filled bars) (n = 6 per group) is expressed as the mean and SD (error bars) of nmol polyamine per mg protein. The data shown are from a single experiment that is representative of 2 independent experiments. The statistical significance of differences in each of the panels is identified by asterisks (*, p<0.05; **, p<0.01; ***, p<0.001).</p
