AIM:To investigate the expression of phosphorylating p38mitogen-activated protein kinase (MAPK) in rat small intestineafter ischemia-reperfusion (I/R) insult and its relationshipwith the localization of intestinal stem cells.METHODS:Forty-eight Wistar rats were divided randomlyinto three groups,namely intestinal ischemia-reperfusiongroup (R),intestinal ischemia group (I) and sham-operatedcontrol group (C).In group I,the animals were killed 45minutes after superior mesenteric artery (SMA) occlusion,while in group R the rats sustained SMA occlusion for 45 minutesand reperfusion for 2,6,12 or 24 hours respectively.In sham-operated control group,SMA was separated,but withoutocclusion.The activity of plasma diamine oxidase (DAO)was determined.Intestinal tissue samples were also takenfor histological analysis and immunohistochemical analysisof MAPK p38 detection and intestinal stem cell localization.RESULTS:The changes in histological structure and plasmaDAO levels indicated that the intestinal barrier was damagedafter intestinal I/R injury.In group C and I,each cryptcontained 5-6 p38 MAPK positive cells,which were mainlylocated in the lower region of the crypts.This was consistentwith the distribution of intestinal stem cells.The presenceof positive cells in crypts increased with the time of reperfusionand reached its peak at 12 hours after reperfusion (35.6 %).CONCLUSION:After intestinal I/R injury,the expressionof phosphorylating-p38 MAPK in small intestine increasedwith the duration of reperfusion,and its distribution coincidedwith that of intestinal stem cells and their daughter cells,indicating that phosphorylating-p38 might be a possiblemarker of intestinal stem cells. AIM: To investigate the expression of phosphorylating p38mitogen-activated protein kinase (MAPK) in rat small intestine after ischemia-reperfusion (I / R) insult and its relationship with the localization of intestinal stem cells. METHODS: Forty-eight Wistar rats were divided randomlyinto three groups I, the animals were killed 45 minutes after superior mesenteric artery (SMA) occlusion, while in group R the rats (group I) and sham-operated control group sustained SMA occlusion for 45 minutes and reperfusion for 2, 6, 12 or 24 hours respectively. In sham-operated control group, SMA was separated, but without occlusion. activity of plasma diamine oxidase (DAO) was determined.Intestinal tissue samples were also takenfor histological analysis and immunohistochemical analysis of MAPK p38 detection and intestinal stem cell localization .RESULTS: The changes in histological structure and plasma DAO levels indicated that the intesti nal barrier was damagedafter intestinal I / R injury. In group C and I, each cryptcontained 5-6 p38 MAPK positive cells, which were mainly located in the lower region of the crypts. This was consistent with the distribution of intestinal stem cells. The presenceof positive Cells in crypts increased with the time of reperfusion and reached their peak at 12 hours after reperfusion (35.6%). CONCLUSION: After intestinal I / R injury, the expression of phosphorylating-p38 MAPK in small intestine increased with the duration of reperfusion, and its distribution coincided with that of intestinal stem cells and their daughter cells, indicating that phosphorylating-p38 might be a possible marker of intestinal stem cells.