Filling Gaps in the Vascular Endothelium with Blood Platelets

Abstract

IN thrombogenesis the interaction between platelets and the wall of the blood vessel is very important. It has been found that after a slight injury to the layer of endothelial cells, platelets adhere to the basement lamina which has been denuded of endothelial cells¹. Other platelets adhere to this first layer and form aggregates. Evidence from in vitro investigations has aided the elucidation of the mechanism of platelet–platelet interaction. This mechanism involves ADP, calcium, fibrinogen and possibly some other agents² in a biological chain reaction³. The mechanism of platelet–vessel wall interaction is not clear. It has been demonstrated in vivo and in vitro that platelets can adhere to collagen fibres^4,5. Nevertheless, in experimental thrombosis where the layer of endothelial cells is the only visible site of injury, platelets adhere exclusively to the basement lamina. Collagen fibres are not involved in this process of adhesion¹. It is not clear from these experiments, however, whether injury to the endothelial cells and the eventual release of tissue factors were necessary for the interaction of platelet with basement lamina.