Figure 3. Irinotecan causes molecular defects in all claudin-1 and occludin in the jejunum of the DA rat. There was no statistically significant change in ZO-1 protein expression in the jejunum. Claudin-1 protein expression was significantly decreased 6 h following irinotecan administration, while occludin expression was downregulated in jejunal crypt epithelium 48 h following treatment. ZO-1, claudin-1, and occludin protein expression was analyzed apical villus, basal villus, and crypt epithelium of the jejunum. Staining intensity was analyzed in a blinded fashion (HR Wardill and RJ Gibson) using a validated semi-quantitative grading system.55 A Kruskall–Wallis with a Dunn multiple comparison was performed to determine significance. Data presented as median values (n = 39); ●■□ P < 0.05 vs. control, ●* P < 0.05 vs. 6 h.