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Active calcium transport in red cell ghosts resealed in dextran solutions
Biochimica Et Biophysica Acta
|December 7, 1981
Summary
Human red blood cells can efficiently remove calcium (Ca) using a powerful extrusion mechanism. This process is influenced by internal calcium levels and various cations, highlighting its adaptability.
Area of Science:
- Cell Biology
- Biochemistry
- Physiology
Background:
- Human erythrocytes (red blood cells) play a crucial role in maintaining cellular homeostasis.
- Calcium (Ca) regulation is vital for various cellular functions, including cell signaling and muscle contraction.
Purpose of the Study:
- To investigate the mechanism of calcium extrusion in human erythrocytes.
- To characterize the kinetics and modulators of the Ca extrusion process.
Main Methods:
- Lysing and resealing human erythrocytes in the presence of dextran to trap Ca.
- Utilizing low-speed centrifugation for separation of resealed ghosts.
- Measuring Ca efflux and ATP hydrolysis under varying Ca concentrations and cation conditions.
Main Results:
- Resealed erythrocyte ghosts effectively retained Ca and EGTA, remaining impermeable to Ca.
- Calcium extrusion was substrate-dependent, with ATP being the most effective, and influenced by internal Ca concentrations.
- The Ca extrusion system exhibited distinct high- and low-affinity states for internal Ca, with specific kinetics.
- Lanthanum-sensitive ATP hydrolysis correlated with Ca efflux, indicating a stoichiometry of 1.6.
- Potassium ions (K+) significantly enhanced Ca extrusion, with other cations like sodium (Na+), choline, and magnesium (Mg2+) showing varied effects.
Conclusions:
- Human red blood cells possess a robust Ca extrusion mechanism.
- The activity of this Ca extrusion system is modulated by internal Ca levels and alkaline cations, particularly K+.