IMPAIRED EPITHELIAL TRANSPORT AND BARRIER FUNCTION IN ULCERATIVE-COLITIS

Ulcerative colitis (UC) is accompanied in most cases with diarrhea. In order to resolve the pathomechanism of this diarrhea, studies on sigm oid colon (obtained after surgical colectomy) were performed in the Us sing chamber. Although tissues were partially stripped, a significant subepithelial resistance remains which may bias conventional resistanc e measurements in an unpredictable way. Therefore, trans-tissue altern ating current impedance analysis was applied to discriminate between t he epithelial (R(e)) and the subepithelial (R(sub)) component of total tissue resistance (R(t)). R(t) was reduced in UC to 61% of that of co ntrol tissues. Most importantly, real epithelial resistance R(e) was d epressed by a factor of more than 4 in UC. Thus, the defect in barrier function in UC is more dramatic than so far indicated by R(t) measure ments. The cause of this discrepancy was that subepithelial resistance (R(sub)) even was increased in UC, most probably due to mucosal edema and infiltration of inflammatory cells. Aldosterone-stimulated electr ogenic Na+ absorption as well as PGE(2)-stimulated electrogenic Cl- se cretion were abolished in UC tissues.