Repair of rabbit duodenal mucosa after acid injury in vivo and in vitro.

Epithelial repair after luminal acid exposure was studied in the rabbit duodenum in vivo and in vitro. Hydrochloric acid (200 mM, 30 min in vivo; 10 mM, 10 min in vitro) caused a uniform damage of the mucosa confined to the villi. After demarcation and detachment of the necrotic tissue the defect was bridged by the remaining viable epithelial cells, resulting in a reduction of villus height. This process of mucosal repair proceeded continuously, so that 9 h after acid damage only 33% of villi in the proximal duodenum and 41% in the distal duodenum remained not fully restored, at both luminal pH 7 and luminal pH 3. The difference is due to the higher acid susceptibility of the distal duodenum. In vitro, most of the mucosal surface was reconstituted 5 h after acid injury, at both luminal pH 7.4 and luminal pH 3. The potential difference declined and reversed after mucosal damage; restitution to original values was only observed at luminal pH 7 in vivo and luminal pH 7.4 in vitro.