A major role for phospholipase A2 in antigen-induced arachidonic acid release in rat mast cells.
Cross-linking of IgE receptors by antigen stimulation leads to histamine release and arachidonic acid release in rat peritoneal mast cells. Investigators have reported a diverse distribution of [3H]arachidonate that is dependent on labelling conditions. Mast cells from rat peritoneal cavity were labelled with [3H]arachidonic acid for different periods of time at either 30 or 37 degrees C. Optimum labelling was found to be after 4 h incubation with [3H]arachidonate at 30 degrees C, as judged by cell viability (Trypan Blue uptake), responsiveness (histamine release) and distribution of radioactivity. Alterations in 3H-radioactivity distribution in mast cells labelled to equilibrium were examined on stimulation with antigen (2,4-dinitrophenyl-conjugated Ascaris suum extract). The results indicated that [3H]arachidonic acid was lost mainly from phosphatidylcholine and, to a lesser extent, from phosphatidylinositol. A transient appearance of radiolabelled phosphatidic acid and diacylglycerol indicated phosphatidylinositol hydrolysis by phospholipase C. Pretreatment with a phospholipase A2 inhibitor, mepacrine, substantially prevented the antigen-induced liberation of [3H]arachidonic acid from phosphatidylcholine. It can be thus concluded that, in the release of arachidonic acid by antigen-stimulated mast cells, the phospholipase A2 pathway, in which phosphatidylcholine is hydrolysed, serves as the major one, the phospholipase C/diacylglycerol lipase pathway playing only a minor role.
D000818:Animals; D000941:Antigens / Q000494:pharmacology*; D000947:Antigens, Helminth; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000493:pharmacokinetics*; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D050356:Lipid Metabolism; D008407:Mast Cells / Q000187:drug effects / Q000378:metabolism*; D010740:Phospholipases / Q000378:metabolism*; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D011796:Quinacrine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
D000941:Antigens; D000947:Antigens, Helminth; D001095:Arachidonic Acids; D005230:Fatty Acids, Nonesterified; D016718:Arachidonic Acid; D010740:Phospholipases; D010741:Phospholipases A; D054467:Phospholipases A2; D011796:Quinacrine