OXYGEN-FREE RADICAL CONTENT AND NEUTROPHIL INFILTRATION ARE IMPORTANTDETERMINANTS IN MUCOSAL INJURY AFTER RAT SMALL-BOWEL TRANSPLANTATION

Mucosal injury is an immediate event following revascularization of sm all intestinal grafts in the context of transplantation (SBTx). The ge neration of oxygen free radicals (OFR) and tissue infiltration by acti vated neutrophils are consequences of ischemia and reperfusion and kno wn causative factors of tissue injury; to delineate their role in the reperfusion injury occurring after cold preservation of the intestine and subsequent transplantation was the aim of this study. Prior to ort hotopic SBTx in Sprague-Dawley rats, grafts were stored in cold (4 deg rees C) Ringer's lactate solution for 1 (n=6), 2 (n=7), and 4 hr (n=7) . Small bowel biopsy specimens were obtained before harvesting, at the end of the (cold) ischemic period and immediately before unclamping ( i.e., before revascularization) and 30, 60, 120 min, and 24 hr after t ransplantation to evaluate tissue injury by histology, OFR production, (measured by luminol-enhanced chemiluminescence [LCL]), and the degre e of neutrophil infiltration by myeloperoxidase staining. Reperfusion of the graft significantly worsened the histologically graded mucosal injury compared with that seen before unclamping. However, 24 hr after engraftment, mucosal morphology was restored almost completely. OFR p roduction increased significantly during the early phases of reperfusi on (30, 60, and 120 min) and returned to control values after 24 hr. R eperfusion of the graft was associated with a marked increase in the n umber of mucosal neutrophils. The present study indicates that OFR pro duction and neutrophilic infiltration commence and progressively incre ase with graft reperfusion. These changes parallel the mucosal injury. Ischemic intervals of 4 hr were not associated with a statistically s ignificant greater ischemic-injury patterns compared with 1- and 2-hr intervals. The profound changes associated with reperfusion probably o vershadow the minor, yet likely, progressive injury patterns associate d with longer ischemia times.