Dictyostelium cells produce platelet-activating factor in response to cAMP

Evidence is provided that Dictyostelium discoideum cells produce 1-O-alkyl-2-delta-acetyl-O-sn-glycero-3-phosphocholine (platelet-activating factor, PAF). D. discoideum PAF has been characterized as being identical with mammalian platelet-activating factor, based on its stimulation of rabbit platelet aggregation, its physicochemical properties and mass spectrum. The basal activity of PAF increases after starvation and during aggregation and declines at the slug stage. PAF is not detected in the extracellular space. Cell treatment with cAMP pulses stimulates a transient accumulation of PAF, probably via activation of a cAMP-dependent acetyltransferase, suggesting a possible involvement of PAF in cAMP-regulated processes in Dictyostelium.