Macrophage activation reduces mobilization of arachidonic acid by guinea-pig and rat peritoneal macrophages in vitro.

We have examined species differences in the mobilization of arachidonic acid and generation of prostacyclin in non-activated and activated peritoneal macrophages in vitro. Mobilization of 3H-arachidonic acid was reduced in rat activated macrophages compared with that in non-activated macrophages, but a similar difference was not observed in guinea-pig macrophages. In guinea-pig peritoneal macrophages, exposure to formyl-Methionyl-Leucyl-Phenylalanine (fMLP), platelet-activating factor (Paf), zymosan and A23187 increased the generation of prostacyclin. In contrast, in rat peritoneal macrophages, fMLP and Paf did not stimulate the mobilization of arachidonic acid or the generation of prostacyclin, whereas both zymosan and A23187 were effective stimuli. Pretreatment of either rats or guinea-pigs by intraperitoneal injection of C. Parvum reduced prostacyclin generation by peritoneal macrophages in vitro. We conclude that there may be species differences in receptor populations between guinea-pig and rat peritoneal macrophages. However, the reduction in eicosanoid generation induced by the inflammatory stimulus, C. Parvum is not species-dependent.