[Platelet aggregation and platelet activating factor (author's transl)].

Platelet aggregation is triggered by at least three distinct pathways. The first one is mediated by adenosine diphosphate, the second one by arachidonic acid metabolites and the third is defined somehow by exclusion of the first two. In fact rabbit platelets synthesize, during their activation, another substance with potent aggregating activity, namely platelet-activating factor or PAF-acether. Indirect pieces of evidence are presented, which suggest that PAF-acether is the mediator of the third pathway of platelet aggregation.