Protective effects of ischemic preconditioning on the intestinal mucosal microcirculation following ischemia-reperfusion of the intestine

Objective: The small bowel villi are extremely sensitive to ischemia-reperfusion (IR) injury and a range of microcirculatory disturbances contribute to structural and functional changes. The aim of this study was to determine the protective effects of ischemic preconditioning (IPC) of the intestine on the mucosal villous microcirculation during IR injury of the intestine and whether heme oxygenase (HO) is involved in the protection. Methods: Rats were allocated into 4 groups: (1) sham, (2) IR consisting of 30 min of ischemia followed by 2 h of reperfusion, (3) IPC, as in IR group, but preceded by 10 min of ischemia and 10 min of reperfusion, and (4) with administration of zinc protoporphyrin, an HO inhibitor before IPC and IR. The mucosa of an exteriorized segment of ileum was visualized. Mucosal perfusion index (MPI), red blood cell (RBC) velocity and leukocyte-endothelial interactions during reperfusion were assessed continuously using in vivo fluorescence microscopy. HO activity in the ileum was assessed at the end of the reperfusion period. Results: IPC improved the MPI by 26% and the RBC velocity by 29% on comparison to IR. IR led to a 52% increase in leukocyte-endothelial interactions on comparison to IPC. The administration of zinc protoporphyrin reversed the beneficial effects of IPC. There was a two fold increase of HO activity in IPC compared to IR, whereas zinc protoporphyrin significantly reduced the HO activity. Conclusions: IPC conferred a protective effect on the villous microcirculation possibly via HO and might prove to be an effective strategy for the amelioration of IR injury.