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 sensitizatio n of rat peritoneal macrophages (treatment of cells by an anti-ovalbum in 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, us ed on [H-3]AA-labeled macrophages, increased cyclooxygenase and lipoxy genase eicosanoid production. Sera. used prior to [H-3]AA incorporatio n, induced a decrease of H-3-labeled membrane phospholipids and an inc rease of lipoxygenase metabolites in the [H-3]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 incorpora ted into membrane phospholipids, we studied the eicosanoid secretion o f [H-3]AA-prelabeled macrophages, treated by the serum and incubated w ith [C-14]AA. It was confirmed that phospholipid-incorporated AA was c atabolised following the cyclooxygenase and lipoxygenase pathways and external AA preferentially following the lipoxygenase pathway. The all ergen increased the eicosanoid formation of passively sensitized macro phages but not that of cells treated by the serum without IgE. Our dat a suggest that changes occurring in passive sensitization, on AA mobil ization from membrane phospholipids and on AA catabolism, induced by t he serum, are independent of IgE and must be taken into consideration on interpreting the allergen effect.