Role of intestinal mucus in transepithelial passage of bacteria across the intact ileum in vitro.

BACKGROUND

Although gastrointestinal mucus is one of a number of putative host defense mechanisms that protect the gut barrier against microbial translocation, little experimental data are available to show its role in this process. The present study sought to determine the role of mucus depletion on the transepithelial passage of bacteria across viable segments of rat ileum mounted in Ussing chambers in vitro.

METHODS

Intestinal mucus was depleted in 12 rats after injection with pilocarpine (160 mg/kg intraperitoneally) 45 minutes before intestinal harvest. The mucosal surfaces of the perfused gut segments mounted in the Ussing chamber were exposed to 5 x 10(9) CFU/ml Escherichia coli C-25. Viability was monitored by continuous measurements of the potential difference generated by the membranes. The electrical characteristics were unaltered by pilocarpine pretreatment or exposure to bacteria.

RESULTS

Bacterial passage occurred in 100% of pilocarpine membranes as compared with 33.3% in controls (p < 0.05). Pilocarpine-treated membranes resulted in 19.9 +/- 7.5 mg of retrievable mucus as compared with 28.8 +/- 7.2 mg in controls (p < 0.05). Light and transmission electron microscopy revealed an intact epithelial surface in all membranes. There was a marked decrease in mucus on the surface of pilocarpine-treated membranes.

CONCLUSIONS

Intestinal mucus secretion is a critical factor in the barrier function of the gut, and its depletion results in a dramatic increase in bacterial passage across the intact rat ileum.