MUCOSAL PERFUSION AND REACTIVITY OF THE RAT SMALL INTESTINAL ALLOGRAFT

During acute rejection (AR), * the endothelial targeting seen in the mucosal vessels of the intestinal allograft (IA) could impair the blood supply and response to luminal stimuli. To study the effect of AR in the perfusion and reactivity of the IA mucosa, we measured the mucosal blood flow in the ileum (IL) of 2 groups of control rats (Lewis and ACI) and in the native and grafted IL of syngeneic (ACI to ACI) and allogeneic (donor ACI to recipient Lewis) rats. Using reflectance spectrophotometry and laser-Doppler flowmetry, parameters of mucosal oxygen saturation (ISO 2 ), hemoglobin content (IHB), and blood flow (FLOW) were obtained at baseline and after saline and 50% dextrose (D50) stimulation. When compared to controls, the isograft IL had similar perfusion (ISO 2 , IHB, and FLOW). The allograft IL showed ischemia (similar ISO 2 , and lower ISO 2 and FLOW). In the allografts, the ISO 2 and FLOW were lower than in the isografts. In response to D50, the native IL of all groups showed an increased IHB and FLOW (hyperemia); the isografts showed an increase only in IHB (partial response) ; the allografts did not show any response at all. In summary, the mucosal perfusion in the rejecting allografts, but not in the isografts, showed ischemia. The response to D50 seen in the native ilea was only partial in the isografts and absent in the allografts. Because these changes occurred before the onset of mucosal ulcerations, we postulate that they could be used as early indicators of AR.