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ATP depletion of blood stored in ACD is associated with the disc‐sphere transformation, fragmentation loss of membrane lipid, decrease in critical hemolytic volume and a striking increase in cellular rigidity reflected by increased viscosity and decreased filterability. Improved survival after restoration of cellular ATP which results from incubation with adenosine is not associated with any reversal of the lipid loss or critical hemolytic volume. Improved survival correlates with restoration of the ATP‐dependent parameters of cell shape (r = 0.96) and deformability as measured by filterability (r = 0.84) and viscosity (r = 0.73). The interrelated parameters of shape and deformability appear critical as determinants of erythrocyte survival. It is suggested that deterioration of these physical properties is central to the “storage lesion.”

A B S T R A C r The turnover of the four major erythrocyte phospholipids has been studied with 32P, both in vivo and in vitro, in man and the dog. Phosphatidyl serine and phosphatidyl ethanolamine appeared to be stable erythrocyte lipids in both species. Turnover of the phosphate moiety of lecithin and sphingomyelin in the circulating erythrocytes of these two species seems entirely due to an exchange of the whole molecule with the corresponding plasma compound. Exchangeable and nonexchangeable pools of these two cellular lipids were found. In man about 60%o of erythrocyte lecithin is exchaigeable. The 12 hr fractional turnover of this pool is approximately 13%. Only 30% of the sphingomyelin in human cells appeared exchangeable; this portion had a 12 hr fractional turnover of about 14%o. Similar results were obtained in the dog except that in this species about 75%o of the erythrocyte sphingomyelin was exchangeable. Inorganic 32P was not incorporated into any of the four major phospholipids in either species. The present findings aid in estimating quantitatively the effect of plasmaerythrocyte lipid exchange on red blood cell phospholipids. INTRODUCTIONThere is now substantial agreement about the major classes and amounts of lipids present in human erythrocytes (2). While hemoglobin and A preliminary report of this work has been presented previously (1).Received for publication 8 August 1967 and in revised form 30 November 1967. structural membrane protein are thought to be stable within the life-span of the circulating mature red blood cell (RBC) (3, 4), a number of reports have indicated that some exchange of erythrocyte lipid with corresponding plasma compounds occurs in various species. Hevesey and Hahn, using the rabbit, (5) were the first to describe an exchange of phospholipids between erythrocytes and plasma. These workers (6) also suggested that the process was probably a slow one, and that all of the erythrocyte phospholipids were not involved equally. British workers have presented suggestive in vitro evidence that phospholipid exchange between cells and plasma occurs in human blood (7,8). More recently such an exchange has been described in the rat by several groups (9-11). In all of the above reports the description of the process has been primarily qualitative, and actual rates of exchange for the individual phospholipids have not been determined. METHODSNormal human donors, patients with uncomplicated polycythemia rubra vera who had received therapeutic orthophosphate-32P, and mongrel dogs were used as subjects. Blood was collected into Na2EDTA (1.25 mg/ml of blood). The red blood cells were washed three times in 5 volumes of cold 0.17 M NaCl and the buffy coat was carefully removed each time. The white blood cell count was less than 500 per cubic mm and platelets were absent from the washed cells. The erythrocyte and plasma lipids were extracted, separated, and quantitated by chromatography on silicic acid-impregnated paper as previously described (12). A modification in the preparation of ...

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