ARACHIDONIC-ACID METABOLISM IN ALVEOLAR MACROPHAGES FROM ACTIVELY SENSITIZED GUINEA-PIGS - EFFECTS OF SENSITIZATION AND SPECIFIC ALLERGEN

Arachidonic acid (AA) metabolism, including mediator release and lipid turnover, was explored in [H-3]AA-radiolabelled alveolar macrophages obtained from guinea-pigs actively sensitized to ovalbumin (sAM) and c ontrols (cAM). The basal and allergen-induced AA metabolism of cAM and sAM were examined in the presence and absence of homologous serum obt ained from the same control or sensitized animals. Basal AA metabolism of cAM and sAM involved the release of lipoxygenase and cylooxygenase [H-3]metabolites and free [H-3]AA into the culture medium. However, i n sAM, the production of free [H-3]AA was significantly lower than in cAM. The allergen had no effect on the basal AA metabolism of cAM and sAM or on the metabolism of cAM and sAM cultured in the presence of co ntrol serum. In contrast, it increased the [H-3]LTC(4)-D-4 and free [H -3]AA production of sAM cultured with sensitized serum but not those o f cAM cultured with the same sensitized serum. In sAM, the allergen ef fect disappeared when the sensitized serum was heated for 1 h to 56 de grees C. Our results suggest that two factors, both induced by the act ive sensitization of guinea-pigs, one in the serum and one on the macr ophages obtained from sensitized guinea-pigs, are required for the all ergen to have an impact on the AA metabolism of alveolar macrophages i n increasing the production of 5-lipoxygenase metabolities.