Arachidonic acid metabolism of rat peritoneal macrophages after passive sensitization and allergen challenge

The aim of our work was to evaluate the effect of passive sensitization of rat peritoneal macrophages (treatment of cells by an anti-ovalbumin IgE-rich serum) on arachidonic acid (AA) metabolism and the impact of specific antigen (ovalbumin) on this process. Compared to a control treatment without serum, the atopic serum and a serum without IgE, used on [3H]AA-labeled macrophages, increased cyclooxygenase and lipoxygenase eicosanoid production. Sera, used prior to [3H]AA incorporation, induced a decrease of 3H-labeled membrane phospholipids and an increase of lipoxygenase metabolites in the [3H]AA incorporation medium. To establish if the serum-induced catabolism of AA differed according to whether it was externally added to the culture medium or incorporated into membrane phospholipids, we studied the eicosanoid secretion of [3H]AA-prelabeled macrophages, treated by the serum and incubated with [14C]AA. It was confirmed that phospholipid-incorporated AA was catabolised following the cyclooxygenase and lipoxygenase pathways and external AA preferentially following the lipoxygenase pathway. The allergen increased the eicosanoid formation of passively sensitized macrophages but not that of cells treated by the serum without IgE. Our data suggest that changes occurring in passive sensitization, on AA mobilization from membrane phospholipids and on AA catabolism, induced by the serum, are independent of IgE and must be taken into consideration on interpreting the allergen effect.