This study demonstrates that treatment with aminoguanidine and L-NAME, both NOS inhibitors, significantly prevented MTX-induced intestinal damage, such as villous atrophy, crypt necrosis and neutrophil infiltration, which is in accordance with a recent study by Kolli et al that suggested that nitrosative stress may play a role in MTX-induced mucositis [18]. This evidence concerns the gene NOS1 and mucositis.