AIM:To elucidate the role of COX-2 in the development ofcapillary leakage in rats with acute interstitial pancreatitis.METHODS:Rats with acute interstitial pancreatitis wereinduced by caerulein subcutaneous injection.Reversetranscription-polymerase chain reaction (RT-PCR) was usedto determine the gene expression of COX-2 in pancreatictissues,spectrophotometry was used to assay the parametersof acute pancreatitis such as the serum amylase and plasmamyeloperoxidase,and determination of capillary permeabilityin the pancreas by quantifying the permeability index (PI)assisted response of pancreatic microvascular via intravitalfluorescence microscope video image analysis system.RESULTS:A significant increase of COX-2 expression,elevation of serum amylase,and plasma myeloperoxidasewere detected in rats with acute edematous pancreatitiscompared with control rats.The changes of pancreaticmicrovascular after caerulein injection were as following:(a)the decrease of pancreatic capillary blood flow (4th h,0.56±0.09 nL/min,P<0.05;8th h,0.34±0.10 nL/min,P<0.001);(b) reduction of functional capillary density (4 th h,381±9 cm~(-1),P>0.05;8th h,277±13 cm~(-1),P<0.001);(c) irregular andintermittent capillary perfusion was observed at the 8th hand these vessels were also prone to permeation.CONCLUSION:COX-2 plays an important role in mediatingcapillary permeability in pancreatitis,thereby contributingto capillary leakage. AIM: To elucidate the role of COX-2 in the development of capillary leakage in rats with acute interstitial pancreatitis. METHODS: Rats with acute interstitial pancreatitis were induced by caerulein subcutaneous injection. Reversetranscription-polymerase chain reaction (RT-PCR) was used to determine the gene expression of COX-2 in pancreatictissues, spectrophotometry was used to assay the parameters of acute pancreatitis such as the serum amylase and plasma myeloperoxidase, and determination of capillary permeability in the pancreas by quantifying the permeability index (PI) assisted response of pancreatic microvascular via intravital fluorescence microscope video image analysis system .RESULTS: A significant increase of COX-2 expression, elevation of serum amylase, and plasma myeloperoxidasewere detected in rats with acute edematous pancreatitiscompared with control rats. The changes of pancreaticmicvascular after caerulein injection were as follows: (a) the decrease of pancreatic capillary blood flow (4th h, 0.56 ± 0.09 nL / min, P <0.05; 8th h, 0.34 ± 0.10 nL / min, P <0.001) (C) irregular and intermittent capillary perfusion was observed at the 8th hand these vessels were also prone to permeation. CONCLUSION: COX-1, P> 0.05; 8th h, 277 ± 13 cm -1, P < 2 plays an important role in mediatingcapillary permeability in pancreatitis, thereby contributing to capillary leakage.