Platelet-activating factor and leukotriene biosynthesis is inhibited in polymorphonuclear leukocytes depleted of arachidonic acid.

Rat peripheral or elicited polymorphonuclear leukocytes 90% deficient in arachidonic acid incorporate, after stimulation with the calcium ionophore A23187, 86% less acetate into platelet-activating factor than control. The total amount of platelet-activating factor in the ionophore stimulated elicited polymorphonuclear leukocytes deficient in arachidonate, measured by gas chromatography-negative ion chemical ionization mass spectrometry, was 84% less than that of control. The mass spectrometry also revealed the presence of various molecular species of platelet-activating factor ranging from 1-O-tetradecyl to 1-O-nonadecyl forms in both the deficient and control cells. However, the 1-O-hexadecyl was the predominate molecular species representing 79 and 96% of the total platelet-activating factor in the respective deficient and control cells. Other molecular species were less than 1.5 and 8.5% of the total for control and deficient polymorphonuclear leukocytes, respectively. Leukotriene B4 formation was also inhibited by 90% in the deficient cells. Both platelet-activating factor and leukotriene B4 biosynthesis could be partially restored in arachidonic acid-deficient cells by prelabeling the cells with arachidonate. This represents the first dietary link with platelet-activating factor biosynthesis.