The incorporation of radioactive fatty acids and of radioactive derivatives of glucose into the phospholipids of subsynaptosomal fractions of cerebral cortex.
1. Crude synaptosomal fractions (P2) from guinea-pig cerebral cortex were incubated in a Krebs-glucose medium containing labelled fatty acids and [3H]glucose. After the shortest incubation period (7.5 min) a high percentage (50-80%) of the total radioactive fatty acids was found in the P2 fractions. 2. After the incubation, the synaptosomal fractions were submitted to hypo-osmotic disruption and subsynaptosomal fractionation was carried out by using discontinuous-sucrose-gradient centrifugation. The specific radioactivities of phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and phosphatidylinositol were determined in fractions D (synaptic vesicles), E (microsomal preparation) and H (disrupted synaptosomes), as were the specific activities of a number of marker enzymes and the distribution of acetylcholine. 3. By using [14C]oleate, [14C]arachidonate, [3H]palmitate and [3H]glucose, the order to specific radioactivities in fraction D was found to be: phosphatidylinositol greater than phosphatidylcholine greater than phosphatidylserine greater than phosphatidylethanolamine. 4. The specific radioactivities of phosphatidylcholine and phosphatidylethanolamine were always higher in fraction D than in fraction E. As fraction E had higher specific activities of several membrane marker enzymes, the enhanced labelling found in fraction D was considered to be localized in the synaptic vesicles. In this fraction, phosphatidylinositol made particularly large contributions to the total phospholipid labelling derived from [14C]arachidonate and [3H]glucose. 5. The similar labelling ratios of fatty acid/glucose in the phospholipids of fractions D and E, and the high specific radioactivities in the total phospholipid of the soluble fraction O, suggested intrasynaptosomal phospholipid transport.
D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D001095:Arachidonic Acids / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism*; D002802:Cholinesterases / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D006168:Guinea Pigs; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008861:Microsomes / Q000378:metabolism; D008995:Monoamine Oxidase / Q000378:metabolism; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009708:Nucleotidases / Q000378:metabolism; D009829:Oleic Acids / Q000378:metabolism; D010168:Palmitates; D010713:Phosphatidylcholines / Q000378:metabolism; D010714:Phosphatidylethanolamines / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism; D010718:Phosphatidylserines / Q000378:metabolism; D010743:Phospholipids / Q000096:biosynthesis*; D013572:Synaptic Vesicles / Q000378:metabolism; D013574:Synaptosomes / Q000378:metabolism*
D001095:Arachidonic Acids; D005227:Fatty Acids; D009419:Nerve Tissue Proteins; D009829:Oleic Acids; D010168:Palmitates; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010716:Phosphatidylinositols; D010718:Phosphatidylserines; D010743:Phospholipids; D007770:L-Lactate Dehydrogenase; D008995:Monoamine Oxidase; D009251:NADPH-Ferrihemoprotein Reductase; D003576:Electron Transport Complex IV; D002802:Cholinesterases; D009708:Nucleotidases; D005947:Glucose; D000109:Acetylcholine