E-type prostaglandins but not iloprost inhibit platelet activating factor-induced generation of leukotriene B4 by human polymorphonuclear leukocytes.

1. Platelet-activating factor (Paf) was found to stimulate leukotriene B4 release from human polymorphonuclear leukocytes (PMN). This stimulation was considerably enhanced in the presence of small amounts of exogenous arachidonic acid. 2. Prostaglandin E2 (PGE2) and PGE1 (0.1-10 microM) inhibited this reaction dose-dependently. No inhibition was seen with iloprost at these concentrations. 3. The data suggest that E prostaglandins are potent inhibitors of Paf-induced leukotriene generation by human PMNs and thus may serve as local factors controlling Paf-mediated inflammatory reactions.