Ischemic preconditioning protects intestine from prolonged ischemia

Ischemic preconditioning (IP), obtained by exposure to brief periods of vascular occlusion, improves organ tolerance to prolonged ischemia. The aim of this study was to evaluate the effects of IP on intestinal morphology. Forty rats were subjected to sham surgery (n = 20, group I) or intestinal preconditioning (n = 20, group II) with a cycle of brief ischemia/reperfusion (10-minute occlusion of superior mesenteric artery [SMA], followed by 10-minute reperfusion) before prolonged ischemia produced by SMA occlusion (45 minutes). Five animals in each group were sacrificed 2, 12, 24, and 48 hours after reperfusion. Intestinal samples were processed for light and electron microscopy. A TUNEL assay was performed to detect apoptosis. Statistical analysis used Student t test and Kaplan-Meier survival curves. The overall mortality for the sham-operated group was 15%, while no animals of group II died (NS). Histological evaluation showed early detachment of epithelial cells from villous stroma accompanied by marked congestion and edema. Successive morphological changes were represented by leukocyte infiltration, focal necrosis, and marked villus denudation or loss. Group II animals showed significantly reduced inflammatory infiltrates in the lamina propria and a greater villus height compared to group I. The maximum number of apoptotic nuclei was observed in both groups, Following 2 hours of reperfusion group II animals showed significantly, greater apoptosis at 2 and 12 hours after reperfusion (P <.05). Electron microscopy showed severe mitochondrial and basement membrane damage. The findings from this study confirm that IP preconditioning attenuates morphological alterations that are invariably present after prolonged ischemia and reperfusion.