Representative images of histological sections through colon specimens from untreated control mice (A), mice exposed to 3% DSS in the drinking water for 5 days (B), mice exposed to 3% DSS and subsequently treated for 5 days with standard powdered clinoptilolite (GHC1; C), with microparticulate clinoptilolite (GHC2; D) or with 5-aminosalicylic acid (ASA; E) and the summary of the histological score (F). Paraffin-embedded sections were stained with hematoxylin and eosin and examined by microscopy to obtain a histological score for each animal (individual values and means ± S.D. are indicated in Panel F) as outlined under Materials and Methods. The DSS group showed extensive damage (B) and an elevated damage score (C). Whereas GHC1 failed to significantly attenuate the inflammation (D), GHC2 showed only mild inflammation (E) and a significantly lower damage score (C). 5-ASA, used as positive control, mitigated the inflammation similar to GHC2 (C and F). Healthy mice, used as control, showed no signs of inflammation (A and C). The statistical comparison was done by ANOVA followed by Tukey’s posthoc test, which showed that there was a significant difference between the following groups: GHC2 vs. DSS (P = 0.025), GHC2 vs. GHC1 (P = 0.045), ASA vs. DSS (P = 0.0025) and ASA vs. GHC1 (P = 0.005). For all groups with the same letter, the difference between the means was not statistically significant. If 2 groups have different letters, they were significantly different (P < 0.05).