Ca2+-translocation activities of phosphatidylinositol, diacylglycerol and phosphatidic acid inferred by quin-2 in artificial membrane systems.
Ca2+-translocating activities of phosphatidylinositol, diacylglycerol and phosphatidic acid were investigated in phosphatidylcholine liposomes. Using a fluorescent indicator of Ca2+ concentration, quin-2, release of encapsulated Ca2+ from egg yolk phosphatidylcholine liposomes containing 2 mol% of one of these lipids was measured at 37 degrees C. The rate of Ca2+ translocation across the liposomal membrane mediated by phosphatidic acid was about 3-fold larger than those mediated by phosphatidylinositol and diacylglycerol. The result implies that phosphatidic acid has Ca2+-ionophore activity in the agonist dependent metabolism of inositol phospholipids. The ionophoretic activity depended on the degree of unsaturation of the fatty acyl chains. The Ca2+ translocation rate was smallest in dipalmitoylphosphatidic acid, and it increased in the order of dioleoyl-, dilinoleoyl- and dilinolenoyl-phosphatidic acid. Ca2+ mobilization of a stimulated cell is discussed in the light of Ca2+-ionophore activity of phosphatidic acid converted from inositol phospholipids.
D000634:Aminoquinolines; D002118:Calcium; D004075:Diglycerides; D004578:Electron Spin Resonance Spectroscopy; D005456:Fluorescent Dyes; D005989:Glycerides; D008081:Liposomes; D008954:Models, Biological; D010712:Phosphatidic Acids; D010713:Phosphatidylcholines; D010716:Phosphatidylinositols; D013050:Spectrometry, Fluorescence; D013329:Structure-Activity Relationship
D000634:Aminoquinolines; D004075:Diglycerides; D005456:Fluorescent Dyes; D005989:Glycerides; D008081:Liposomes; D010712:Phosphatidic Acids; D010713:Phosphatidylcholines; D010716:Phosphatidylinositols; C035739:Quin2; D002118:Calcium