EFFECT OF A GLYCEROL-CONTAINING HYPOTONIC MEDIUM ON ERYTHROCYTE PHOSPHOLIPID ASYMMETRY AND AMINOPHOSPHOLIPID TRANSPORT DURING STORAGE

Previous studies from our laboratory have shown that under blood bank storage conditions red blood cell (RBC) ATP and lipid content were bet ter maintained in a glycerol-containing hypotonic experimental additiv e solution (EAS 25) than in the conventional storage medium Adsol (R). The objective of this study was to determine the mechanism of the pro tective effect of EAS 25, by measuring transmembrane phospholipid asym metry and the membrane integrity of stored RBCs. Split units of packed RBCs were stored in either EAS 25 or Adsol (R). RBCs were analyzed af ter 0, 42, and 84 days and vesicles shed from stored RBCs were analyze d after 84 days of storage. Phospholipid asymmetry was measured by pho spholipase A(2) digestion (RBCs) and activation of the prothrombinase complex (RBCs, vesicles). RBC membrane exhibited a significantly great er (P < 0.01) amount of phosphatidylethanolamine externalized after st orage in Adsol (R) than in EAS 25 (44.3% +/- 11.7 vs. 25.3% +/- 5.7, r espectively). Prothrombin converting activities in RBCs were significa ntly lower than in shed vesicles (P < 0.001) suggesting the presence o f phosphatidylserine in the outer monolayer of vesicle, but not in RBC membranes. The rates of inwardly-directed aminophospholipid transport in RBCs decreased by similar to 50% and glutathione levels decreased by similar to 50% in both media. RBC cholesterol and phospholipid cont ent of stored RBCs remained significantly greater (P < 0.01) in EAS 25 than in Adsol (R). The results indicate that despite comparable reduc tion in the rate of aminophospholipid transport and reduced GSH concen trations, RBC phospholipid asymmetry was better maintained during stor age in EAS 25 than in Adsol (R). The data suggest that glycerol in the hypotonic EAS helps preserve RBC lipid organization and membrane inte grity during storage. (C) 1997 Elsevier Science B.V.