The effects of aspirin and OKY-1581 on the metabolism of exogenous arachidonic acid in rat alveolar macrophages.

When non-stimulated rat alveolar macrophages were incubated with exogenous 14C-arachidonic acid (7 microM) both cyclo-oxygenase and lipoxygenase metabolites were formed. The major cyclo-oxygenase metabolites were PGE2, PGF2 alpha and TXB2. The detected amounts of 5-lipoxygenase metabolites were small. Aspirin inhibited the formation of all cyclo-oxygenase metabolites, but had no effect on the formation of the lipoxygenase metabolites. In the presence of OKY-1581, an inhibitor of thromboxane synthetase, the formation of thromboxane B2 was decreased and that of the other cyclo-oxygenase metabolites was correspondingly increased. The present study indicates that OKY-1581 is a specific inhibitor of thromboxane synthetase also in rat alveolar macrophages and that the rate of formation of leukotrienes via the 5-lipoxygenase pathway is rather small in non-stimulated rat alveolar macrophages.