Ca2+-translocation activities of phosphatidylinositol, diacylglycerol and phosphatidic acid inferred by quin-2 in artiifical membrane systems
✍ Scribed by Kazuo Ohki; Shunji Nagaoka; Masaru Sogami; Yoshinori Nozawa
- Publisher
- Elsevier Science
- Year
- 1986
- Tongue
- English
- Weight
- 694 KB
- Volume
- 39
- Category
- Article
- ISSN
- 0009-3084
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✦ Synopsis
Ca2+-translocating activities of phosphatidylinositol, diacylglycerol and phosphatidic acid were investigated in phosphatidylcholine liposomes. Using a fluorescent indicator of Ca 2÷ concentration, quin-2, release of encapsulated Ca a+ from egg yolk phosphatidylcholine liposomes containing 2 mol% of one of these lipids was measured at 37°C. The rate of Ca ~÷ 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 Ca 2÷ translocation rate was smallest in dipalmitoylphosphatidic acid, and it increased in the order of dioleoyl-, dilinoleoyl-and dilinolenoyl-phosphatidic acid. Ca 2÷ mobilization of a stimulated cell is discussed in the light of Ca=÷-ionophore activity of phosphatidic acid converted from inositol phospholipids.