Effect of aminoguanidine and L-NAME on myeloperoxidase (MPO) activity in the duodenum, jejunum and ileum segments of rats submitted to intestinal mucositis. Bars represent the mean value ± standard error of the mean (SEM) of the MPO units/mg of tissue. *p < 0.05 represents statistical differences compared to MTX group (-). The number of animals in each group was at least six. Data were analyzed by using analysis of variance (ANOVA) and Bonferroni tests.