Blood, Vol. 95 No. 6 (March 15), 2000:
pp. 2164-2168
Dehydration of mature and immature sickle red blood cells during
fast oxygenation/deoxygenation cycles: role of KCl cotransport and
extracellular calcium
Anthony J. McGoron,
Clinton H. Joiner,
Mary B. Palascak,
William J. Claussen, and
Robert
S. Franco
From the Department of Radiology and the Division of
Hematology/Oncology, Department of Internal Medicine, University of
Cincinnati College of Medicine; Children's Hospital Research
Foundation; and the Comprehensive Sickle Cell Center, Cincinnati, OH.
Sickle red blood cells (RBC) become dehydrated as a consequence of
potassium loss. This process depends at least partly on deoxygenation
and may be influenced by the presence of oxygenation/deoxygenation cycles and the frequency of cycling. In this study, sickle RBC were
subjected to approximately 180 oxygenation/deoxygenation cycles during
4 hours to evaluate RBC dehydration with cycle periods more similar to
in vivo cycles than those in previous studies. A continuous-flow,
steady-state apparatus circulated a dilute RBC suspension through
gas-permeable silicone tubing with segments that were exposed to either
nitrogen or ambient oxygen. The percentage of sickling and partial
pressure of oxygen were measured by means of sampling ports in the
deoxygenation and oxygenation regions. The density increase
(dehydration) of young (transferrin receptor-positive) and mature
(transferrin receptor-negative) RBC and the requirements for calcium
and chloride were evaluated. Density increase correlated with the
percentage of sickled cells at the deoxygenation sampling port and was
observed only in the presence of calcium, thereby implicating the
calcium-dependent potassium channel (Gardos pathway). Density increase
was not dependent on the presence of chloride, making it unlikely that
KCl cotransport was an important pathway under these conditions.
