Effects of chronic alcohol exposure on expression of tight junction proteins in mice. A: mRNA levels of tight junction proteins. The mRNA levels of claudin-1, occludin, and ZO-1 were measured by real-time RT-PCR. The gene expressions, normalized to β-actin, were expressed as relative changes, setting the values of duodenum as one. Results are means ± SD (n = 4). Significant differences (P < 0.05) among intestinal segments were determined by ANOVA and are indicated by different letters. *Significant differences (P < 0.05) between alcohol-fed and pair-fed mice for each intestinal segment determined by t-test. B: correlations between mRNA levels of HNF-4α and tight junction proteins. Correlation coefficients were used to determine linear association between intestinal HNF-4α and tight junction protein mRNA variables.