Defective ADP-induced platelet factor 3 activation in uremia.

P ATIENTS \VITH UREMIA frequently have both prolonged bleeding times,11#{176} suggesting poor platelet plug formation, and impaired prothrombin consumption,1’2’46’#{176}14 ascribed to defective platelet factor 3 activalion. Considerable evidence points to the presence of a qualitative platelet defect in uremia, since such abnormalities cannot be attributed to the mild thrombocytopenia occasionally encountered.13’1 4 The exact nature of this defect has not been defined. Adenosine 5’diphosphate ( ADP ) plays a central role in the formation of the platelet plug ‘ and also activates platelet factor 3,15.19 accelerating fibrin formation.’1 ”#{176} Thus, a defective response to ADP in uremia could account for most of the hemostatic abnormalities observed. In this study we report the presence of an inhibitory factor in uremic plasma which interferes with ADP-induced platelet factor 3 activation. Preliminary studies suggest that this may be a newly