Phospholipid Metabolism in Some Excitable Biological Membranes
Triphosphoinositide, a constituent of myelin and plasma membranes, may be important in binding calcium ions. The purification to homogeneity of a phosphatase from brain which removes the 4- and 5-phosphate groups of this phospholipid is described. In iris muscle, acetylcholine activates the breakdown of triphosphoinositide, the effect being blocked by atropine but not tubocurarine. The related lipid phosphatidylinositol was most highly labelled in vivo in the membrane of transmitter vesicles from brain synaptosomes. Electrical stimulation of synaptosomes caused rapid breakdown of this phosphatidylinositol and of phosphatidic acid in another sub-synaptosomal membrane fraction. Possible functions of these lipids in transmitter release are discussed.
KeywordsElectrical Stimulation Phosphatidic Acid Transmitter Release Specific Radioactivity Phosphatidyl Inositol
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