title: Influence of calcium on arachidonic acid mobilization by murine resident peritoneal macrophages.
abstract: Stimulation of resident peritoneal macrophages resulted in release of arachidonic acid (AA) from phospholipids. This AA release is believed to occur as a result of the activation of phospholipases, usually by a phospholipase A2 (PLA2). The purpose of this study was to elucidate the role of cytosolic calcium ion concentration ([Ca2+]i) in the modulation of [3H]AA mobilization in peritoneal macrophages. [3H]AA release induced by ionophore A23187, opsonized zymosan, or 4 beta-phorbol 12-myristate acetate (PMA) occurred in the absence of extracellular calcium. Studies in fura-2/AM-loaded cells showed that zymosan and PMA did not increase [Ca2+]i significantly, whereas A23187 induced PLA2 activity translocation up to plasmatic membrane. Thapsigargin, an inhibitor of endomembrane Ca(2+)-ATPase, induced a rise in [Ca2+]i when cells were incubated in a Ca2+ medium. However, thapsigargin was not an effective stimulator of the translocation of PLA2 activity and [3H]AA release. These data indicate that changes in [Ca2+]i were not sufficient to elicit [3H]AA mobilization; this process seems tightly modulated by phosphorylation-dependent mechanisms in the presence of low [Ca2+]i.
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002462:Cell Membrane / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D017737:Macrophages, Peritoneal / Q000378:metabolism*; D008297:Male; D051379:Mice; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D011493:Protein Kinase C / Q000378:metabolism; D013729:Terpenes / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019284:Thapsigargin
chemical_list: D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D007476:Ionophores; D013729:Terpenes; D016718:Arachidonic Acid; D000001:Calcimycin; D019284:Thapsigargin; D011493:Protein Kinase C; D010741:Phospholipases A; D054467:Phospholipases A2; D000252:Calcium-Transporting ATPases; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium