title: Activation of NADPH-oxidase by arachidonic acid involves phospholipase A2 in intact human neutrophils but not in the cell-free system.
abstract: The mechanism involved in the stimulation of NADPH-oxidase by arachidonic acid (AA) in intact human neutrophils was studied and compared with that involved in a cell-free system. [3H]-AA was released from pre-labeled cells upon AA stimulation, and phospholipase A2 inhibitors reduced in parallel the release of [3H]-AA and superoxide. Cyclooxygenase, lipoxygenase or protein kinase inhibitors failed to affect either response. In a cell-free system, no release of [3H]-AA was observed after AA addition, whereas NADPH-oxidase was activated; the generation of superoxide was not inhibited by phospholipase inhibitors and was not initiated by adding phospholipase A2 to the preparation. Thus AA stimulates NADPH-oxidase through a phospholipase A2 mediated pathway in intact cells, but activates the oxidase independent of phospholipase A2 in a broken cell system, suggesting distinctive mechanisms of activation for each system.
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000494:pharmacology*; D002474:Cell-Free System; D016861:Cyclooxygenase Inhibitors; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D007546:Isoquinolines / Q000494:pharmacology; D016859:Lipoxygenase Inhibitors; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D019255:NADPH Oxidases; D009504:Neutrophils / Q000201:enzymology*; D019301:Oleic Acid; D009829:Oleic Acids / Q000378:metabolism; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D010879:Piperazines / Q000494:pharmacology; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011796:Quinacrine / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism; D014213:Tretoquinol / Q000494:pharmacology
chemical_list: D001095:Arachidonic Acids; D016861:Cyclooxygenase Inhibitors; D007546:Isoquinolines; D016859:Lipoxygenase Inhibitors; D009829:Oleic Acids; D010879:Piperazines; D011450:Prostaglandin Endoperoxides, Synthetic; D013481:Superoxides; D016718:Arachidonic Acid; D019301:Oleic Acid; C024531:1-(2',4',5-trimethoxybenzyl)-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases; D011493:Protein Kinase C; D010741:Phospholipases A; D054467:Phospholipases A2; D011796:Quinacrine; D014213:Tretoquinol