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Control of red blood cell hydration

Carlo Brugnara, MD
Section Editor
Stanley L Schrier, MD
Deputy Editor
Jennifer S Tirnauer, MD


The volume and hemoglobin concentration of human red blood cells are determined by the red cell content of hemoglobin, ions, and water. The water, cation, and anion contents are continuously regulated by the activity and interactions of several ion transport systems, as summarized in the figure (figure 1). The importance of these systems is indicated by the various diseases occurring when red cell ion transport is impaired (table 1).

The transport systems involved in regulating the volume and composition of red cells, and which affect the cation, anion, and water content of the red cell, will be discussed here [1,2]. A brief discussion of the role of ion transport in the pathogenesis of sickle cell disease will also be presented.

Cation content — In human red cells (and other cells), the activity of the sodium-K-ATPase pump maintains a low sodium, high potassium milieu. The outward potassium gradient and the inward sodium gradient can be used by several passive (gradient-driven) transport systems, which are sensitive to changes in pH, volume, or membrane integrity.

Human red cells have a high content of total magnesium but a lower content of free magnesium. Magnesium is an important regulator of several cellular functions; its export from the red cells is regulated by a gradient-driven Na-Mg exchanger, while little is known about the mechanisms involved in controlling the entry of magnesium into the human erythrocyte.

A powerful membrane Ca-ATPase is responsible for the extremely low Ca content of human erythrocytes.

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Literature review current through: Nov 2017. | This topic last updated: Oct 18, 2017.
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