Cell age-related monovalent cations content and density changes in stored human erythrocytes

Conversion of erythrocyte membrane protein 4.1b to 4.1a occurs through a no n-enzymatic deamidation reaction in most mammalian erythrocytes, with an in vivo half-life of approximately 41 days, making the 4.1a/4.1b ratio a usef ul index of red cell age [Inaba and Maede, Biochim. Biophys. Acta 944 (1988 ) 256-264]. Normal human erythrocytes distribute into subpopulations of inc reasing cell density and cell age when centrifuged in polyarabinogalactan d ensity gradients. We have observed that, when erythrocytes were stored at 4 degreesC under standard blood bank conditions, the deamidation was virtual ly undetectable, as cells maintained the 4.1a/4.1b ratio they displayed at the onset of storage. By measuring the 4.1a/4.1b values in subpopulations o f cells of different density at various time points during storage, a modif ication of the normal 'cell age/cell density' relationship was observed, as erythrocytes were affected by changes in cell volume in an age-dependent m anner. This may stem from a different impact of storage on the imbalance of monovalent cations, Na+ and K+, in young and old erythrocytes, related to their different complement of cation transporters. (C) 2001 Elsevier Scienc e B.V. All rights reserved.