Relationships between base-exchange reaction and synaptosomal phospholipid pool in the rabbit brain in vitro.
The calcium-stimulated incorporation of ethanolamine, L-serine and choline into rabbit synaptosomal phospholipids in vitro has been investigated. The synaptosomal membranes were prelabelled in vitro in their choline-, ethanolamine- or serine-phosphoglycerides by base-exchange and then chasing experiments were performed by displacing the lipid-bound base by ethanolamine, choline of L-serine labelled with a different isotope. The results indicate that membrane phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine are substrates for the exchange with all the three mentioned bases. A very small phospholipid pool (0.5-2% of the total available pool) is active in the calcium-dependent exchange between membrane phosphatidylcholine or phosphatidylethanolamine and free bases, whereas the pool of exchanging phosphatidylserine molecules is sensibly larger (2-9%). The possible physiological importance of these small phospholipid pools, involved in base-exchange reaction at brain membrane level, is discussed.
D000818:Animals; D001921:Brain / Q000378:metabolism*; D002250:Carbon Radioisotopes; D002794:Choline / Q000378:metabolism; D004983:Ethanolamines / Q000378:metabolism; D007553:Isotope Labeling; D007700:Kinetics; D010743:Phospholipids / Q000378:metabolism*; D011817:Rabbits; D012694:Serine / Q000378:metabolism; D013574:Synaptosomes / Q000378:metabolism*; D014316:Tritium
D002250:Carbon Radioisotopes; D004983:Ethanolamines; D010743:Phospholipids; D014316:Tritium; D012694:Serine; D002794:Choline