Desensitisation of human blood platelets to the effects of 1-O-alkyl-2-acetyl-sn-glyceryl-3-phosphorylcholine (1-O-alkylAcGEPC) and palmityl-lysophosphatidate by pre-incubation with these agonists has no effect on the aggregatory or secretory responses to collagen but causes 30–40% inhibition of these responses to thrombin in aspirin-treated platelets. The effects of 1-O-alkylAcGEPC and palmitoyl-lysophosphatidate are not additive. The results are not consistent with the proposal that 1-O-alkylAcGEPC or lysophosphatidate are the mediators for the responses to collagen observed when prostaglandinendo-peroxide synthesis is prevented, although they may play some role in the responses to thrombin under these conditions.
