title: Histopathologic evidence of reperfusion injury in the large colon of horses after low-flow ischemia.
abstract: Effects of low-flow ischemia and reperfusion of the large colon on mucosal architecture were determined in horses. Twenty-four adult horses were randomly allocated to 3 groups: sham-operated (n = 6), 6 hours of ischemia (n = 9), and 3 hours of ischemia and 3 hours of reperfusion (n = 9). Low-flow ischemia was induced in horses of groups 2 and 3 by reducing colonic arterial blood flow to 20% of baseline values. Systemic hemodynamic and metabolic variables were maintained constant and in a normal physiologic range. Full-thickness biopsy specimens were obtained from the left ventral colon for histomorphologic and morphometric examination at baseline and at 30-minute intervals for 6 hours; additional biopsy specimens were collected at 185, 190, and 195 minutes (corresponding to 5-, 10-, and 15-minute periods of reperfusion in group-3 horses). There were no differences among groups at baseline or across time in group-1 horses for any of the histopathologic variables. There were significant (P < 0.05) increases in percentage of surface mucosal disruption, estimated and measured percentage depth of mucosal loss, mucosal hemorrhage, mucosal edema, and cellular debris index during 0 hour to 3 hours, compared with baseline, and from 3 hours to 6 hours, compared with 3 hours in horses of groups 2 and 3. Estimated percentage depth of mucosal loss and cellular debris index were significantly (P < 0.05) greater in group-3 horses, compared with group-2 horses during the interval from 3 to 6 hours. There were trends toward greater percentage of surface mucosal disruption and mucosal edema during the early phase of reperfusion (3 to 4 hours) and greater mucosal hemorrhage, measured percentage depth of mucosal loss, and mucosal interstitial-to-crypt ratio during the late phase (4 to 6 hours) of reperfusion in group-3 horses vs group-2 horses. Reestablishment of colonic arterial blood flow after low-flow ischemia caused greater mucosal injury than did a comparable period of continued ischemia. Thus, reperfusion injury was detected in the large colon of horses after low-flow arterial ischemia. The serial mucosal alterations that developed in the colon were comparable in horses of groups 2 and 3; however, reperfusion exacerbated colonic mucosal injury.
authors.affiliation: Department of Veterinary Clinical Sciences, Ohio State University, Columbus 43210-1089.
authors.forename: R M
authors.initials: RM
authors.lastname: Moore
authors.forename: A L
authors.initials: AL
authors.lastname: Bertone
authors.forename: W W
authors.initials: WW
authors.lastname: Muir
authors.forename: P C
authors.initials: PC
authors.lastname: Stromberg
authors.forename: W L
authors.initials: WL
authors.lastname: Beard
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D017091:Colitis, Ischemic / Q000662:veterinary; D003106:Colon / Q000098:blood supply / Q000473:pathology*; D005260:Female; D006734:Horse Diseases / Q000473:pathology*; D006736:Horses; D007413:Intestinal Mucosa / Q000473:pathology; D007511:Ischemia / Q000473:pathology / Q000662:veterinary*; D008297:Male; D015427:Reperfusion Injury / Q000473:pathology / Q000662:veterinary*