deamino-arginine-vasopressin and Constriction--Pathologic

Von Willebrand Factor (vWF) is essential for normal haemostasis involving platelet aggregation induced by high shear forces. In vitro a functional test of platelet aggregation using the filterometer is abnormal in von Willebrand's disease. However in normal people there is no significant correlation between the antigenic assay of vWF and the filter results. To study this discrepancy normal blood before and during venous occlusion, and blood before and after infusion of 1 deamino-(8-D-arginine) vasopressin was studied. During venous occlusion (VO) the increase in vWF due to the release of large multimers correlated precisely with the increase in the filterometer results. That this was due to the plasma vWF and not to any change induced in the platelets was shown as follows: The methodology was altered so that a small amount of the donor's platelet-poor plasma (PPP) was added to homologous normal substrate blood. The effect of the added donor's PPP was then shown to be closely correlated to the increase in the antigenic assay. Analysis of vWF multimer size showed during VO an increase in large multimers. We conclude that the effect of vWF on normal blood may be obscured by variation in platelet aggregability. In the filterometer system as elsewhere the large active multimers probably play a major part in causing platelet adhesion, aggregation and filter blocking. The filterometer test is influenced by the amount of vWF antigen, by the molecular size and activity of the vWF and by platelet sensitivity. Clinically this is a useful global test.

Topics: Adult; Aged; Aged, 80 and over; Antigens; Case-Control Studies; Constriction, Pathologic; Deamino Arginine Vasopressin; Dimerization; Female; Filtration; Humans; Male; Middle Aged; Platelet Aggregation; Platelet Function Tests; Stress, Mechanical; Veins; von Willebrand Diseases; von Willebrand Factor

A radioimmunoassay (RIA) has been set up using purified human melanoma tissue plasminogen activator and a specific antiserum raised against it. Concentration of antigen in citrated plasma of resting human subjects was found to be 7.1 +/- 1.6 ng/ml (mean +/- S.D.) while the lower limit of sensitivity of the RIA was 2 ng/ml. After venous occlusion or DDAVP infusion the levels of antigen were invariably elevated and a significant increase in the proportion of antigen having fibrin binding properties was observed. Decay studies in vitro and gel filtration of post-stimulus plasma indicated that the RIA detects active and inactive forms of antigen and the possible nature of the inactive antigen is discussed.

Topics: Arm; Chromatography, Gel; Constriction, Pathologic; Deamino Arginine Vasopressin; Fibrin; Fibrinolysis; Hemostatics; Humans; Infusions, Parenteral; Male; Peripheral Vascular Diseases; Radioimmunoassay; Reproducibility of Results; Tissue Plasminogen Activator