Introductory Remarks to the First Session

Abstract

As an introduction, it may be useful to review current thinking on the mechanism of platelet function (Fig. 1) (Salzman, E. W., 1971, Fed. Proc. 30:1503). Platelets do not adhere to normal endothelium, but in areas of endothelial denudation, as at the end of a lacerated blood vessel or on an atherosclerotic arterial plaque, they adhere to subendothelial connective tissue, probably to collagen or a collagen-like material, and are then induced to undergo a secretory process, the “release reaction”. Not a non-specific disruption of the platelet surface but a selective secretion of the contents of certain intracellular granules, the release reaction leads to expulsion from the platelet of biogenic amines such as cat echolamines and serotonin and activation of other substances with biological activity. These include platelet factor 4 (PF 4), an antiheparin, and platelet factor 3 (PF 3), an alteration in the lipid component of the platelet surface that serves to accelerate the intrinsic clotting system.