Is the pro-adhesive activity of plasma von Willebrand factor counteracted by a physiological inhibitor of platelet adhesiveness?

1. Abnormal plasma levels of von Willebrand factor are accompanied by abnormal platelet function in some disease states. 2. Platelet retention in glass bead columns, platelet aggregation in vitro, beta-thromboglobulin and 6-oxo-prostaglandin F1 alpha were monitored in six normal male volunteers before and after an acute rise of von Willebrand factor, as induced by the intravenous administration of 1-deamino 8-D-arginine vasopressin (DDAVP). 3. After DDAVP a steady twofold rise of von Willebrand factor occurred. Platelet retention increased by 74% immediately after DDAVP but returned to baseline values within 60-120 min. No consistent changes of the other variables were observed. 4. These results suggest that as yet unidentified mechanism(s) inhibits the pro-adhesive activity of von Willebrand factor.