Circulating von Willebrand Factor Antigen as a Predictor of Short-term Prognosis in Pulmonary Hypertension
A large multimeric glycoprotein, von Willebrand factor (vWF), synthesized exclusively by endothelial cells and megakaryocytes. It is found in the endothelial basement membrane, where it serves to anchor platelets and endothelial cells to the matrix.
vWF also is present in plasma, where it acts as a carrier for coagulation factor VIII, and within platelet a-granules as an adhesive protein. Within endothelial cells, vWF has been identified in the cytoplasm, on the plasma membrane, in the endoplasmic reticulum, and, particularly, in cell-specific organelles called Weibel-Palade bodies.
In physiologic conditions, vWF is released from endothelial cells into the plasma and to the albu-minal cell surface, where it binds to the subendothelium. Buy ampicillin Reading here After secretion into the plasma, endothelial cell-derived vWF is converted by cleaving activities present in granulocytes into a series of multimers with molecular masses from 500 kd to as high as 20,000 kd.2 In pathological conditions, endothelial cell stimulation by a number of agents, such as thrombin, fibrin, histamine, epinephrine, vasopressin, endotoxin, cytokines, components of the complement system, and shear stress, is followed by a rapid release of vWF from storage granules into the circulation. For this reason, plasma antigenic activity of vWF (vWF:Ag) has been used widely as a marker of endothelial cell injury. Increased plasma vWF:Ag has been reported in several disorders associated with microvascular damage, including scleroderma, thrombotic thrombocytopenic purpura,, nephritis pregnancy-induced hypertension, myocardial infarction, diabetic angiopathy, and pulmonary hypertension. During the course of bacterial, viral, and parasitic infections, vWF participates as an acute-phase reactant. In these instances, a significant elevation occurs in plasma vWF: Ag in addition to the hepatic components of the acute-phase response. Moreover, plasma vWF:Ag has been used as a predictor of lung involvement in nonpulmonary sepsis syndrome. Elevated plasma vWF:Ag has been shown to be predictive of mortality in this disorder.