DDAVP Does not Induce the Release of Thrombomodulin from Endothelial Cells

The endothelial cell surface membrane protein thrombomodu- lin (TM) binds thrombin with high affinity and acts as a cofactor for thrombin-catalyzed activation of anticoagulant protein C. When complexed with TM, thrombin loses its procoagulant activities (L ,2). A soluble form of TM is present in human plasma (3) and presumably represents a cleaved form of vascular TM with loss of part of the O-glycosylation site-rich region, the transmem- brane domain and the cytoplasmic tail. Although its clinical relevance has not been sufficiently evaluated yet, circulating TM would be a new endothelial cell marker which may reflect either stimulation or injury of endothelial cells. It is well known that desmopressin acetate (1-deamino-8-D-arginine vasopressin, DDAVP) induces the release of von Wille- brand factor (vwf) and tissue-type plasminogen activator (t-PA) from endothelial cells when administered into humans (4). We measured plasma levels of TM following DDAVP infusion together with vWf and t-PA. DDAVP (Ferring Pharmaceuticals AB, Malmo, Sweden) was infused into L3 patients with miscel-laneous bleeding disorders at a dose of 0.4 pglkg in 20 ml saline over 20 min. Citrated plasma samples were prepared prior to and at 30 min,