Objective      To investigate the role of  microparticles derived from vascular endothelial cells in vascular leakage in rats after sepsis.       Methods      Sepsis rat model was prepared by cecal ligation and puncture(CLP) operation. The microparticles obtained from sepsis rats were identified by flow cytometry and transmission electron microscopy. The change of vascular leakage and the concentration of microparticles were detected. Meanwhile

the effects of microparticles obtained from sepsis rats and different cells (vascular endothelial cells

platelets and neutrophil granulocytes) on vascular leakage and endothelial cell permeability

and the relationship with tight junction were analyzed.       Results      The vascular permeability of lung

kidney and intestine and the concentration of blood microparticles were all increased significantly after sepsis in rats (P0.05). Microparticles obtained from sepsis rats enhanced the vascular permeability of lung

kidney and intestine (P0.01). Microparticles derived from LPS-stimulated vascular endothelial cells increased the pulmonary vascular permeability significantly (P0.05)

while microparticles derived from LPS-stimulated platelets and neutrophil granulocytes showed no such effect. Meanwhile

vascular endothelial cell-derived microparticles reduced the transmembrane electric resistance of monolayer pulmonary vein endothelial cells (P0.01) and the expression of tight junction protein ZO-1 (P0.05).       Conclusion      Endothelial cell-derived microparticles play an important role in the vascular leakage after sepsis

which is closely related to the tight junction among vascular endothelial cells.