Platelet-activating factor (PAF-acether): Thromboxane-independent synergism with adrenaline on human platelets and recent insights into its mode of action

The mode of action of PAF-acether on human and rabbit plasma-free platelets is reviewed. PAF acether and adrenaline synergize to trigger aggregation of human platelets, and this synergism is refractory to aspirin. When degranulated rabbit platelets are stimulated with PAFacether, with thrombin or with the snake venom component convulxin, aggregation is obtained in the absence of detectable secretion. Collagen-induced aggregation is reduced, and is suppressed when aspirin is applied to the degranulated platelets. The formation of PAF-acether by platelets, and their stimulation by PAF acether itself, should be added to the newly recognized pathways for platelet stimulation.