Changes of occludin expression in intestinal mucosa after burn in rats

In severely burned rats, hyperemia, edema and other pathological injuries occur in the intestinal mucosa. Ultramicroscopically, the microvilli, tight junction and organelles are disrupted. Occludin is a functional component of tight junctions. The purpose of the present study is to investigate changes of occludin expression, and to further elucidate the relationship between occludin expression and ultrastructure damage. The fluorescence intensity of occludin was detected in intestinal wall by the method of immunofluorescence histochemistry and confocal laser scanning microscopy (CLSM). Expression of occludin and its mRNA were determined by western blotting and RT-PCR, respectively. Changes of intestinal mucosa ultrastructure were observed by TEM. The results showed that fluorescence intensity of occludin at 3PBH was enhanced, higher than that of the control group, being 80.77+/-8.38 and 72.86+/-4.74, respectively, and reached a peak at 12PBH (116.14+/-6.89). The expression levels of occludin at 3PBH and 6PBH were 1.21+/-0.02 and 1.53+/-0.14 times that of the control group, respectively, and there were significant differences (P<0.01) between 3PBH group and 6PBH group and control group. The levels of occludin mRNA were also enhanced. At 12PBH, the level reached a peak (P<0.01), being 2.00+/-0.24 times that of the control group. Coincidently, the structure of the tight junction between epithelial cells was disrupted on a large scale under TEM. We speculate that up-regulation of epithelial occludin may play a role in enhancing paracellular permeability and be related to the damage to the tight junction.