Bioadhesive properties of polygalacturonides against colonic epithelial membranes.

Diseases of the gastrointestinal system are often related with irritations or pathological changes of mucous membranes. In an ex vivo system based on porcine colonic tissue various neutral and acidic polysaccharides were tested concerning their bioadhesive potential in order to form artificial mucin layers on colon epithelial membranes. Rhamnogalacturonans with a low degree of esterification and linear oligogalacturonids derived from pectin showed significant bioadhesion against colonic mucous membranes. In contrast highly esterified pectins and neutral polysaccharides were ineffective. Within a structure-activity relationship linear, strongly acidic homogalacturonides were shown to be most adhesive agents. Esterification, branching or non-linear backbone structures will reduce the adhesive properties. The bioadhesive effects were concentration-dependent. Polysaccharide layers, located exclusively on the apical membrane surface of colonic tissue, were visualized by fluorescent microscopy. The adhesion of the exogenous galacturonides on the tissue surface was mediated by interaction with the endogenous mucin, for the release of the endogenous mucines with a mucolytic agent resulted in a decreased bioadhesion of exogenous galacturonides. Additionally, mucin-galacturonide synergism was shown by rheological methods. The artificial mucin layers provide protective effects on colonic mucous membranes against toxic agents as shown by incubation of the tissue with TritonX-100.