A method to prepare isotonic dextran-salt solutions.

Area of Science:

• Biophysics
• Hematology
• Materials Science

Background:

• High-molecular-weight polymers like dextrans increase viscosity in red cell rheological studies.
• Dextrans contribute significantly to osmotic pressure, necessitating electrolyte concentration adjustments for normal red cell volume.
• Traditional osmometry of dextran-salt solutions is unreliable due to increased viscosity.

Purpose of the Study:

• To devise a reliable method for determining electrolyte concentrations in dextran-salt solutions (DSSs) for red cell rheology.
• To maintain normal red cell volume when using DSSs in rheological experiments.
• To establish the relationship between dextran molecular weight and required electrolyte concentration.

Main Methods:

• Developed a novel method using red blood cells as osmometers to determine required electrolyte concentrations.
• Added packed, unwashed red cells to DSSs with varying electrolyte concentrations.
• Monitored red cell swelling or shrinking via changes in the suspending medium's refractive index.

Main Results:

• The required electrolyte concentration for normal red cell volume was independent of dextran molecular weight (40 kDa to 2000 kDa).
• For 15% (w/w) dextran solutions, electrolyte addition needed reduction by approximately 1/4 compared to isotonic pure electrolyte solutions.
• The red cell osmometer method proved effective in determining optimal electrolyte levels.

Conclusions:

• A red cell-based osmometry method reliably determines electrolyte concentrations for DSSs.
• This method ensures stable red cell volume, crucial for accurate rheological studies.
• Findings provide a practical approach for preparing physiological suspending media for red blood cell research.