DESMOPRESSIN (DDAVP) ACTS ON PLATELETS TO GENERATE PLATELET MICROPARTICLES AND ENHANCED PROCOAGULANT ACTIVITY

Desmopressin (DDAVP), an analog of vasopressin (AVP), has wide clinica l application as an anti-hemorrhagic (AH) agent. DDAVP in vivo release s vWF from endothelial cells but is reported to have little action on platelets. However, DDAVP is often used to improve hemostasis in plate let dysfunctions. We examined the effect of DDAVP on platelet micropar ticle (PMP) formation and procoagulant activity in vitro using platele ts from normal volunteers and in vivo in six patients receiving DDAVP therapy. In the former, platelets were incubated with DDAVP (0.5 to 25 nM) and PMP released were stained with FITC-labeled MAb alpha-GP IIb/ IIIa for flow cytometry. Procoagulant activity was measured in a clot- based assay using Russel's viper venom (RVV) calibrated with cephalin. A mean increase of 2-3 fold was observed in both PMP and procoagulant activity. Parallel to these observations was a dose-dependent rise in organelle-associated Ca2+. The assays were also performed on six pati ents prior to and at one hour after infusion of DDAVP, and similar but lesser effects were observed. We conclude that DDAVP acts on platelet s in vitro, and that these effects may contribute to the hemostatic ac tion of DDAVP in platelet dysfunctions in vivo.