On the existence of platelet receptors for factor V(a) and factor VIII(a).

The surface of the platelet expresses procoagulant phospholipids that bind coagulation factors and contribute to the procoagulant activity of the cell. The evidence, however, also suggests that platelets may possess specific receptors for coagulation Factors V(a) and VIII(a). Examination of a limited set of the available data could lead to the controversial position that the procoagulant surface of platelets is defined exclusively by either procoagulant phospholipids, or specific receptors for the cofactors and proteases. At the present time insufficient data exist to exclusively support one or the other of these possibilities. Further work, however, should indicate clearly whether the putative receptors exist and what role they play, either alone or in concert with surface phospholipids, in the expression and regulation of platelet procoagulant activity.