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Cell age-related monovalent cations content and density changes in stored human erythrocytes
G Minetti1, A Ciana, A Profumo
1Dipartimento di Biochimica, Sezione di Scienze, Università di Pavia, Italy. minetti@unipv.it
Insights
Red blood cell age can be tracked by the ratio of protein 4.1a to 4.1b. Storage at 4°C halts this conversion, altering cell volume and age relationship.
Area of Science:
- Biochemistry
- Hematology
- Cell Biology
Background:
- Erythrocyte membrane protein 4.1b converts to 4.1a via non-enzymatic deamidation.
- This deamidation has an in vivo half-life of ~41 days, making the 4.1a/4.1b ratio an index of red cell age.
- Normal erythrocytes stratify by density and age in density gradients.
Purpose of the Study:
- To investigate the effect of cold storage on erythrocyte protein 4.1a/4.1b ratio.
- To determine if cold storage alters the relationship between erythrocyte age and density.
Main Methods:
- Storing erythrocytes at 4°C under blood bank conditions.
- Centrifuging erythrocytes in polyarabinogalactan density gradients.
- Measuring the 4.1a/4.1b ratio in density-defined subpopulations over time.
Main Results:
- Deamidation of protein 4.1b to 4.1a was undetectable during cold storage.
- Erythrocytes maintained their initial 4.1a/4.1b ratio throughout storage.
- Cold storage modified the age/density relationship, showing age-dependent changes in cell volume.
- This effect may relate to storage-induced imbalances in monovalent cations (Na+/K+).
Conclusions:
- Cold storage prevents the age-dependent deamidation of erythrocyte protein 4.1b.
- The age-dependent changes in cell volume observed during storage are linked to cation transport differences between young and old erythrocytes.
Abstract:
Conversion of erythrocyte membrane protein 4.1b to 4.1a occurs through a non-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 useful index of red cell age [Inaba and Maede, Biochim. Biophys. Acta 944 (1988) 256-264]. Normal human erythrocytes distribute into subpopulations of increasing cell density and cell age when centrifuged in polyarabinogalactan density gradients. We have observed that, when erythrocytes were stored at 4 degrees C under standard blood bank conditions, the deamidation was virtually 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 of cells of different density at various time points during storage, a modification of the normal 'cell age/cell density' relationship was observed, as erythrocytes were affected by changes in cell volume in an age-dependent manner. 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.