Metabolism of red-cell lipids I. Incorporation in vitro of fatty acids into phospholipids from mature erythrocytes

Erythrocytes freed from leucocytes and reticulocytes were demonstrated to incorporate fatty acids into their phosphoglycerides. This ability was decreased in the order rat, rabbit, man, ox and sheep. Lysis of the cells caused an increase of the rate of incorporation thereby abolishing the differences between erythrocytes of different species. Addition of coenzyme A and adenosine 5'-triphosphate promoted the fatty acid uptake, particularly in the lysates. In rabbit erythrocytes linoleic, oleic and palmitic acid were incorporated to a greater extent than stearic, myristic and lauric acid. The unsaturated fatty acids were esterified predominantly at the 2-ester position, whereas palmitic acid was directed to the I-position of lecithin. By contrast to -α-glycerophosphate, lysolecithin stimulated the incorporation of linoleic acid into lecithin of lysates of rabbit erythrocytes. The possible relation between the fatty acid uptake in vitro and the fatty acid renewal of phosphoglycerides from circulating erythrocytes is discussed