Platelet‐Activating Factor (PAF‐Acether) Secretion from Platelets: Effect of Aggregating Agents

Platelet-activating factor is a 1.0-alkyl-2 acetyl analogue of phosphatidylcholine (PAF-acether) which triggers platelet aggregation independently from ADP release and thromboxane A2 (TxA2) formation. PAF-acether was described initially as being secreted by rabbit basophils during an immunological challenge. We have now found that it is also formed by washed rabbit platelets stimulated by the calcium ionophore A23187, thrombin and collagen. These three agents are known to trigger platelet aggregation independently from the release of ADP and from the formation of TxA2. By contrast, ADP and arachidonic acid, the precursor of TxA2, which do not share these properties, and PAF-acether itself, were unable to induce PAF-acether formation. Our results suggest that PAF-acether may be the mediator responsible for ADP and TxA2 independent-aggregation.