L-arginine improves clinical parameters, mucosal integrity, and PMN inflammatory cell infiltration in DSS-induced colitis.

<p>7-week-old C57BL/6 mice received 4% DSS in the drinking water or water alone (Ctrl) for 6 days, followed by administration of 1% L-Arg in the drinking water, or water alone for 4 days. (A) Body weights of the mice were measured daily and presented as a percentage of their initial body weight. **<i>p</i><0.01, ***<i>p</i><0.001 vs. DSS. (B) Survival analysis, with mortality based on >20% body weight loss. **<i>p</i><0.01 vs. Ctrl. §§§<i>p</i><0.001 vs. DSS. (C) At sacrifice, colons were removed, cleaned, and weighed. The fresh colon weight was determined as a percentage of the total body weight. ***<i>p</i><0.001 vs. control and §§§<i>p</i><0.001 vs. DSS. In A–C, <i>n</i> = 4–11 for controls, <i>n</i> = 27–32 for treatments. (D) Prior to sacrifice, mice were anesthetized and given FITC-labeled dextran via rectum. Blood was obtained by cardiac puncture at 2 h. Fluorescence was measured in the serum at 482 nm and 528 nm. In (D), <i>n</i> = 4–8 for controls, <i>n</i> = 14–16 for treatments. **<i>p</i><0.01 vs. control. (E) and (F) At sacrifice, colons were removed, cut open longitudinally, cleaned, Swiss-rolled and formalin fixed for future staining with MPO antibody. (E) The number of MPO-positive PMNs per HPF were counted. 20 HPFs per slide were assessed. (F) Representative photomicrographs of MPO staining after DSS treatment alone or DSS followed by L-Arg supplementation. <i>n</i> = 4 for controls, <i>n</i> = 9–10 for treatments. **<i>p</i><0.01, ***<i>p</i><0.001 vs. control. §§<i>p</i><0.01 vs. DSS.