Immunoblot analysis of tight junction (TJ) proteins in the whole cell extracts of the Caco-2 cell monolayers incubated with or without rat bile juice (10 and 20%, A and B) and fat emulsion (0.5 and 1.0%, A and C) for 72 h. The whole cell extracts were prepared 72 h after the start of incubation and immunoblotted for occludin, claudin-1, claudin-3, junctional adhesion molecules-1 (JAM-1), and β-actin. Specific bands of occludin, claudin-1, claudin-3, and JAM-1 were quantitated by densitometric analysis. The density values were normalized to the value obtained for the control monolayers. Each value represents mean ± SEM, n = 6. Means without a common letter differ, P < 0.05. P values estimated by 1 way ANOVA were < 0.01 in each TJ protein expression in the cells treated with the rat bile juice (A) and fat emulsion (B).