Objective—To induce ischemia and reperfusion injury in the large colon mucosa of horses in vivo and evaluate the recovery and effects of components of an organ transplant solution on mucosal recovery in vitro. Animals—6 healthy horses. Procedures—Horses were anesthetized, and ischemia was induced for 60 minutes in the pelvic flexure, which was followed by reperfusion for 240 minutes. Ischemic (n = 4 horses), reperfused (6), and adjacent control (6) colonic mucosae were isolated for in vitro testing and histologic examinations. Tissues were mounted in Ussing chambers with plain Krebs Ringer bicarbonate (KRB), KRB with N-acetylcysteine (NAC), or KRB with a modified organ transplant solution (MOTS). Transepithelial electrical resistance (TER) and mannitol flux were used to assess mucosal integrity. Data were analyzed by use of ANOVA and Kruskal-Wallis tests. Results—The TER in reperfused tissues was similar to the TER in control tissues and greater than the TER in ischemic tissues, which was consistent with morphological evidence of recovery in reperfused tissues. Mannitol flux was greater in ischemic tissues than in reperfused tissues. The TER and mannitol flux were not significantly affected by incubation of mucosa with NAC or MOTS. Conclusions and Clinical Relevance—Ischemia induced during the brief period allowed rapid mucosal repair and complete recovery of tissue barrier properties during reperfusion. Therefore, reperfusion injury was not observed for this method of ischemic damage in equine colonic mucosa.

Objective—To compare secretory responses to prostaglandin (PG) E2 in mucosa obtained from the proximal and distal portions of the colon of dogs. Sample—Colonic mucosa from cadavers of 18 clinically normal adult dogs. Procedures—Short-circuit current (ISC) and maximum change in ISC (ΔIsc) in response to administration of 1μM PGE2 were measured across mucosa obtained from the proximal and distal portions of the colon. Responses were evaluated in mucosa (n = 6 dogs) incubated in Ussing chambers with or without 1 mM amiloride or without chloride in the Ringer's bathing solution. Responses were also evaluated in mucosa (n = 9 dogs) incubated with or without pretreatment with 1 μM indomethacin, with or without amiloride in the subsequent bathing solution. Histologic changes in mucosa from 3 dogs were assessed over time. Results—ISC and ΔISC were significantly reduced when chloride was removed from, but not when amiloride was added to, the bathing solution and were significantly reduced after pretreatment with indomethacin. The ΔISC was significantly greater in mucosa from the distal portion of the colon than in the proximal portion of the colon. Histologic changes after incubation for 3 hours were minimal. Conclusions and Clinical Relevance—ISC and ΔISC resulted from electrogenic chloride secretion. Chloride secretion was reduced when release of PGs was prevented by indomethacin and was induced by administration of PGE2. Chloride secretion in response to PGE2 was greater in mucosa from the distal portion of the colon than in mucosa from the proximal portion of the colon.

The objectives of this study were to determine the effect of bacterial culture conditions on adherence of enterohemorrhagic Escherichia coli (EHEC) O157:H7 strain 86-24 in vivo to pig enterocytes and to compare the results with adherence in vitro to cultured HEp-2 and IPEC-J2 cells. Growth of O157:H7 in MacConkey broth (MB) resulted in almost no adherence to both HEp-2 and IPEC-J2 cells; prior exposure of the bacteria to pH 2.5 reduced adherence. There was greater adherence by bacteria from static cultures than by those from shaken cultures and by bacteria cultured in brain-heart infusion (BHI) plus NaHCO3 (BHIN) than by bacteria cultured in BHI. In contrast, in pig ileal loops, bacteria cultured in MB adhered well to enterocytes, and prior exposure to pH 2.5 had no effect on adherence. Among several media tested for their effect on bacterial adherence in the pig intestine, MB and BHIN proved to be the best. Bacterial adherence was dose-dependent and was more extensive in the ileum than in the colon. This study demonstrated that there are remarkable differences between culture conditions that promote adherence of an EHEC O157:H7 strain in vitro and in vivo, that culture conditions profoundly affect adherence to epithelial cells in vitro and in vivo, and that pig ileal loops are better suited to adherence studies than are colon loops.

Objective—To examine the expression and distribution of tight junction (TJ) and adherens junction (AJ) proteins in canine duodenal and colonic mucosa. Sample—Mucosa obtained from 4 healthy Beagles. Procedures—Biopsy specimens of the duodenum and colon were obtained via endoscopy from 4 healthy dogs. The expression patterns and subcelluar localization of claudin-1, -2, -3, -4, -5, -7, and -8; E-cadherin; and β-catenin in the duodenum and colon were analyzed by use of immunoblotting and immunofluorescence microscopy. Results—In the duodenum, there was clear expression of claudin-3 and -5, E-cadherin, and β-catenin proteins and weak expression of claudin-7 protein. In contrast, there was clear expression of claudin-2 and -3, E-cadherin, and β-catenin proteins and weak expression of claudin-5 and -7 proteins in the colon, as determined by use of immunoblotting. As determined by the use of immunofluorescence microscopy, the duodenum and colon had staining for claudin-3 and -5, E-cadherin, and β-catenin in the most apical region and staining for claudin-7 in the basolateral region. Staining for claudin-2 was also observed in the colon. Conclusions and Clinical Relevance—Information was provided about the expression patterns of TJ and AJ proteins in the duodenum and colon of clinically normal dogs. These results may provide valuable information for use in evaluating the importance of these TJ and AJ proteins in the pathogenesis of inflammatory bowel disease in dogs.