Platelet activating factor (PAF) induces the oxidative burst in macrophages.

The response of guinea pig peritoneal macrophages to platelet activating factor (1-O-octadecyl-2-acetyl-sn-glycero-3-phosphoryl-choline) was examined. In Corynebacterium parvum induced macrophages, platelet activating factor, over a wide dose range (3.8 X 10(-5) to 3.8 X 10(-9)M) triggered the oxidative burst as indicated by increased luminol-dependent chemiluminescence and hydrogen peroxide release into culture supernatants. This effect of PAF was inhibited by superoxide dismutase and catalase. Resident macrophages exhibited only slight respiratory activity in response to platelet activating factor which could be increased by adding 1% gelatine to the medium. Activation of macrophages is a new biological effect exerted by platelet activating factor. In immuno-inflammatory reactions, cells capable of generating platelet activating factor may come into close contact with macrophages and by liberating this mediator cause them to release highly toxic oxygen species known to be microbicidal and cytocidal and able to produce vascular endothelial injury. Our findings lend further support to the view that platelet activating factor is a potent and rapid activator of physiological defence mechanisms.