Alterations in Metabolic Energetics and Cation Transport During Aging of Red Cells

Abstract

With the total life span of the human red cell averaging 120 days, about 0.8 per cent of the circulating erythrocytes disintegrate daily. Normal red cell destruction has been attributed to extra-and intracorpuscular factors (1, 2); until recently, little attention has been paid to the intrinsic processes of impaired function in normal red cells that may lead to possible disintegration. The metabolic energy of the red cell is predominantly derived from glycolytic mechanisms and is utilized to maintain transport and membrane functions and to prevent the auto-oxidation of hemoglobin (3). This investigation was designed to ascertain whether alterations in glycolysis and the activity of certain crucial enzymes concerned in the Embden-Meyerhof path occur with the in vivo aging of circulating red cells.Centrifugation of blood aggregates young red cells (including reticulocytes) in the top layers of the packed red cell column (4, 5). Examination of layers of centrifuged red cells after Fe59 administration reveals that, five to 15 days later, high radioactivity is incorporated in the top fraction, while at subsequent stages in the life span, the greatest radioactivity is present in the bottom layer (6, 7). Fractionation of red cell samples on the basis of increasing density of the erythrocyte population with age has revealed decreases in content of water, solids and cations (4,8), lipids (7) and enzyme activity (5) MATERIALS AND METHODSHeparinized blood from humans (normal and in response to hemorrhage) was collected in plastic or siliconed glass for centrifugation in blood cell separation tubes at 500 G for 15 minutes; the plasma was removed for respinning to obtain a cell-free preparation and the buffy coat completely removed from the constricted part of the tube. The red cells from the bottom bulb of the tube were suspended in isotonic saline (either buffered or containing dextran or 20 per cent bovine albumin) to make a 40 per cent suspension, and a portion, constituting the original red cells, retained for analysis. After standing for 10 minutes, the remainder of the suspension was spun at 100 G for 10 minutes, followed by 2,000 G for 45 minutes. Where necessary, the estimations detailed have been corrected for the intercellular fluid trapped between the packed cells at different levels in the centrifuged cell column by the Evans blue method (13) in a separate sample spun under identical conditions.

Monovalent cation transport in irreversibly sickled cells.

“…In this figure we (38,40), but in each instance there hat this increase represented a compensatory appears to be at least some absolute increase in Na, response to increased passive permeability (31). We ascribe the abnormally high transport rates observed by those authors to the dominating effect of reticulocytes (28,29). The passive permeability measurements from the same study are not directly comparable to ours because they were performed in isotonic sucrose solutions at low ionic strength.…”

Properties of the Na+-K+ pump in human red cells with increased number of pump sites.

“…The number of pumps per cell or per unit membrane area in reticulocytes and in stem cells ofthe erythroid series is much higher than the number present in the mature human red cell (28). Red cell maturation seems to involve, among other important developments, the loss of active pump units from the membrane.…”

Effect of 2,3-diphosphoglycerate on oxygen affinity of blood in sickle cell anemia

“…2B). DPG concentrations are said to be increased in reticulocyte-rich blood (10,42) (13,14), is also difficult to explain on DPG concentration alone, for oxygen affinities as low as those found in these patients (A A, [12][13][14] were not found at the DPG levels found in their red cells (6.6-14.9 /smole/ml).…”