A plasma factor for platelet adhesiveness and clot retraction acceleration.

By J. PHILIP SAVITSKY, M.D. C HANGES in platelet adhesivemiess have been noted during the course of many different clinical conditions.t4 Imicreased platelet adhesiveness has been correlated by some investigators with a predisposition to thromboembolic phemiomena and vascular disease,2 but other work has not confirmed this suiggestion.3 It has been show’mi that there is a very close relation between the level of the platelet adhesiveness amid the rate of imsit.iation of clot retraction as measured by the clot retraction time.5 The number and morphology of the platelets and the extent of clot retraction ‘ere found to be unrelated to the platelet adhesiveness and the clot retraction time.5 These observations suggested that there might be a substance outside the platelets which makes them adhesive and accelerates the initiation of clot retractioui. Wright has suggested that fibrin, which is constantly being formed imitravascularly, coats the platelets, making them more adhesive.6 No evidence, how’ever, for this hypothesis has been offered and it has been observed that the fibrinogen level has no relation to platelet adhesiveness or clot retraction time.5 This present investigation attempts t.o demonstrate the existence of a factor circulating in the blood outside the platelets which acts to increase platelet adhesiveness and accelerate clot retraction. Some of the properties of this factor are studied and their relationship to the “viscous metamorphosis” of the platelets, described by Wright and Minot in 1917, is clarified.7