Effects of cardiopulmonary bypass on tight junction protein expressions in intestinal mucosa of rats.

AIM

To investigate the tight junction protein expressions of intestinal mucosa in an experimental model of cardiopulmonary bypass (CPB) in rats.

METHODS

Thirty anesthetized rats were randomly divided into two groups: Group S (n = 10) served as sham operation and group C (n = 20) served as CPB which underwent CPB for 1 h. Expression of occludin and zonula occludens-1 (ZO-1) were determined by Western blotting and immunotochemistry, respectively. Plasma levels of diamine oxidase (DAO) and d-lactate were determined using an enzymatic spectrophotometry.

RESULTS

Immunohistochemical localization of occludin and ZO-1 showed disruption of the tight junctions in enterocytes lining villi at the end of CPB and 2 h after CPB. The intensities of the occludin and ZO-1 at the end of CPB were lower than those of control group (76.4% +/- 22.5% vs 96.5% +/- 28.5% and 62.4% +/- 10.1% vs 85.5% +/- 25.6%, P < 0.05) and were further lower at 2 h after CPB (50.5% +/- 10.5% and 45.3% +/- 9.5%, P < 0.05). Plasma d-lactate and DAO levels increased significantly (8.688 +/- 0.704 vs 5.745 +/- 0.364 and 0.898 +/- 0.062 vs 0.562 +/- 0.035, P < 0.05) at the end of CPB compared with control group and were significantly higher at 2 h after CPB than those at the end of CPB (9.377 +/- 0.769 and 1.038 +/- 0.252, P < 0.05). There were significant negative correlations between occludin or ZO-1 expression and DAO (r(2) = 0.5629, r(2) = 0.5424, P < 0.05) or d-lactate levels (r(2) = 0.6512, r(2) = 0.7073, P < 0.05) both at the end of CPB and 2 h after CPB.

CONCLUSION

CPB markedly down-regulates the expression of occludin and ZO-1 proteins in intestinal mucosa of rats. The close correlation between expression of tight junctions (TJs) and plasma levels of DAO or d-lactate supports the hypothesis that intestinal permeability increases during and after CPB because of decreases in the expressions of TJs.