The effect of deoxygenation rate on the formation of irreversibly sickled
cells
K Horiuchi, SK Ballas and T Asakura
Children's Hospital of Philadelphia, Division of Hematology, PA 19104.
The effects of the deoxygenation rate on the formation of irreversibly
sickled cells (ISCs) were investigated by using metabolically replete
sickle cells (SS cells). We found that the formation of ISCs required Ca2+
and that the amount formed depended on the rate of deoxygenation. When less
dense SS discocytes were deoxygenated slowly by flushing with 95% N2 and 5%
CO2 at a rate of 3 mL/min, the percentage of ISCs increased from 5% to
26.5% after 24 hours. In contrast, upon rapid deoxygenation (10, 35 mL/min)
ISC formation was reduced significantly. The difference may be related to
fact that more sickle-shaped cells were formed upon slow deoxygenation than
upon the rapid deoxygenation that resulted in the formation of star-shaped
and granulated cells. So- called ISCs were formed more easily from
sickle-shaped cells. To express the shape of sickled cells numerically, we
calculated the mean maximum cell length (MCL) after cells were incubated
under various deoxygenation conditions. The MCL of slowly deoxygenated SS
cells after 24 hours of incubation was about twice (20.0 +/- 7.0 micron)
that of quickly deoxygenated (35 mL/min) SS cells (12.5 +/- 5.0 microns)
(initial MCL, 8.0 +/- 1.0 micron). The decrease in potassium content was
greater with slow deoxygenation than with rapid deoxygenation. Because the
increase in sodium influx was less than that of potassium efflux under slow
deoxygenation, SS cells became more dense than those rapidly deoxygenated.
In the absence of Ca2+, morphological changes were the same as in the
presence of Ca2+; however, under this condition there was no change in
density, and no ISCs were formed regardless of the rate of deoxygenation.
These results demonstrate that the number of ISCs formed correlates with
the MCL. The length of fibers of sickle hemoglobin may be a determinant of
the length of sickled cells. This suggests that membrane stretching plays
an important role in cell density and irreversible membrane deformation.
Volume 71,
Issue 1,
pp. 46-51,
01/01/1988
Copyright © 1988 by The American Society of Hematology
