Distinct phospholipases A sub(2) regulate the release of arachidonic acid for eicosanoid production and superoxide anion generation in neutrophils

Arachidonic acid (AA) released from membrane phospholipids by phospholipase A sub(2) (PLA sub(2)) is important as a substrate for eicosanoid formation and as a second messenger for superoxide anion (O sub(2) super(-)) generation in neutrophils. Different isoforms of PLA sub(2) in neutrophils might mobilize AA for different functions. To test this possibility, we sought to characterize the PLA sub(2)s that are activated by the neutrophil stimuli, Aroclor 1242, a mixture of polychlorinated biphenyls, and A23187, a calcium ionophore. Both Aroclor 1242 and A23187 caused release of [ super(3)H]AA; however, O sub(2) super(-) production was seen only in response to Aroclor 1242. Eicosanoids accounted for >85% of the radioactivity recovered in the supernatant of A23187-stimulated cells but 80% by BEL, whereas calcium-dependent activity was inhibited