[Interactions between the platelets and the vessel wall. Part 1: Physiology (author's transl)].

The vessel wall plays an important role in the maintenance of balance between haemorrhage and thrombosis. The endothelial lining of a normal vessel wall is thrombo-resistant, in particular by virtue of prostacyclin, whilst the sub-endothelium with its collagen is thrombogenic. If the endothelium is pathologically or experimentally damaged, adhesion of the blood platelets becomes possible. This mechanism, presently studied at a molecular level itself, involves the Willebrand factor, the glycoproteins of the platelet membrane and constituents of the sub-endothelium which remain poorly defined. Platelet adhesion is responsible for cellular activation with the liberation of numerous intraplatelet constituents and synthesis of prostaglandins. Agregation between platelets involves complex biochemical phenomena which concern the platelet membrane and fibrinogen, contractile proteins and the cyclic AMP system, prostaglandins and ADP. The role of calcium in these different phenomena is very important.