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Calcium extrusion by high-density human red blood cells
1Department of Laboratory Medicine, University of California, San Francisco 94143.
Blood Cells
|January 1, 1988
Summary
Very dense human red blood cells show reduced ATP levels, but maintain normal calcium extrusion capacity. This indicates intact cellular transport systems in even the oldest red blood cells.
Area of Science:
- Hematology
- Cell Biology
- Biochemistry
Background:
- Red blood cells (RBCs) undergo aging, leading to changes in cellular components and function.
- Density gradient separation is a method to isolate RBC populations based on age and characteristics.
Purpose of the Study:
- To investigate the adenosine triphosphate (ATP) content and calcium (Ca) extrusion capacity of very high-density human RBCs.
- To compare these properties with a mature, low-density RBC reference population.
Main Methods:
- Human RBCs were separated using arabinogalactan density gradients.
- ATP content was assayed in freshly drawn and separated cell populations.
- Ca extrusion was measured in high- and low-density cells loaded with 45Ca using the ionophore A23187.
Main Results:
- The most dense 0.5%-1% of RBCs exhibited an approximate 40% decrease in ATP concentration.
- The second most dense RBC population showed no significant ATP deficit.
- Both high- and low-density RBC populations demonstrated equivalent rates of Ca extrusion.
Conclusions:
- Stringently selected, very high-density human RBCs retain an intact Ca transport system.
- Rapid Ca export is possible in these cells when sufficient metabolic support is available.
- Aging RBCs may maintain critical transport functions despite reduced ATP levels.