To study the catabolism of erythrocyte phospholipids, human erythrocytes were labeled with radioactive fatty acid (FA). Labeling was performed by the two separate routes which together are thought to be responsible for the majority of phosphatide renewal in the red cell: (a) passive equilibration of erythrocytes with preformed acid-labeled red cell phosphatidylcholine (PC) and (b) active, “acylase”-dependent, incorporation of free fatty acid in the presence of ATP coenzyme A and magnesium. (As measured here “acylase” = the over-all effect of fatty acid thioesterification and the action of acyl-CoA: acylglycerophosphoryl acyltransferase.) The labeled cells were then reincubated in serum and the loss of radioactivity from cells into serum was examined.
