Glutamine- and phosphate-containing hypotonic storage media better maintain erythrocyte membrane physical properties

We have shown that red blood cell (RBC) adenosine-5'-triphosphate (ATP) is better maintained and that there is less hemolysis and K+ leakage in hypotonic experimental additive solutions (EASs) containing glutamine and glutamine plus phosphate (Pi) than in the conventional additive solution Adsol during blood bank storage. The objective of this study was to determine if the beneficial effect produced in these media correlates with better preservation of RBC membrane properties including lipid content, phospholipid organization, aminophospholipid transport (flippase), and prothrombin converting activity. Aliquots of packed RBCs were stored in EASs containing adenine, glucose, sodium chloride, and mannitol, with 10 mmol/L glutamine (EAS 44) or with 10 mmol/L glutamine and 20 mmol/L Pi(EAS 45), or in Adsol. RBC membranes were studied after 0, 28, 42, and 84 days of storage, and vesicle membranes were studied after 84 days. RBC cholesterol and phospholipid content remained significantly greater (P < .01) in EASs than in Adsol. The degree of membrane vesiculation was more than 50% lower in EASs than in Adsol (P < .01). After 42 days of storage, the accessibility of phosphatidylethanolamine to phospholipases was approximately 1.5 times greater for Adsol and EAS 44 samples than for EAS 45 samples (43.5% v 28%). The rates of phosphatidylserine transport were 43% to 70% lower for stored cells but were not dependent on storage media. The amounts of bands 3 and 4.1 in the microvesicle membranes were not statistically different in any of the preparations. These results suggest that storage of RBCs in glutamine and Pi-medium better maintains ATP, lipid content, and phospholipid asymmetry and results in decreased vesiculation.