Inactivation of platelet activating factor by rabbit platelets. Lyso-platelet activating factor as a key intermediate with phosphatidylcholine as the source of arachidonic acid in its conversion to a tetraenoic acylated product.

Abstract [3H]PAF (platelet activating factor or 1-alkyl-2-acetyl-GPC) is converted to 1-alkyl-2-lyso-GPC and 1-alkyl-2-acyl-GPC by rabbit platelets (GPC is sn-glycero-3-phosphocholine). The deacetylation reaction does not involve the transfer of the acetate of PAF to any other lipid class and added exogenous lyso-PAF readily mixes with the cellular pool of the [3H]lyso-PAF intermediate formed from [3H]PAF. [3H]1-Alkyl-2-acyl-GPC produced during the inactivation of [3H]PAF contained primarily the tetraenoic acyl species (approximately 80% of the 3H in this fraction). The source of the arachidonic acid used for the reacylation of the lyso-PAF intermediate is the diacyl species, phosphatidylcholine.