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Hematological and blood viscosity changes in tail-suspended rats
David K Saunders1, Adam C Roberts, Kevin J Aldrich
1Department of Biological Sciences, Emporia State University, KS 66801, USA. saunderd@emporia.edu
Aviation, Space, and Environmental Medicine
|July 26, 2002
Summary
Microgravity exposure causes fluid shifts, initially increasing hematocrit and potentially blood viscosity. However, red blood cell mass reduction normalizes hematocrit, suggesting a mechanism to maintain optimal oxygen delivery.
Area of Science:
- Physiology
- Space Medicine
- Hematology
Background:
- Microgravity induces fluid shifts, decreasing plasma volume and transiently increasing hematocrit.
- This can elevate blood viscosity, but red blood cell mass reduction quickly normalizes hematocrit.
- Rat tail-suspension models simulate microgravity's hematological effects.
Purpose of the Study:
- To investigate hematological and hemorheological changes in rats during simulated microgravity.
- To understand the relationship between hematocrit and blood viscosity under these conditions.
Main Methods:
- Tail-suspended rats were monitored for hematological and hemorheological parameters at various time points (4-168 hours).
- Recovery phases (48-192 hours) post-suspension were also analyzed.
- Blood viscosity was measured and compared to theoretical values at higher hematocrits.
Main Results:
- While hematocrit increased early in suspension, blood viscosity did not initially differ from controls.
- Blood viscosity significantly increased at later time points (72, 168 hours) despite stable hematocrits.
- Theoretical models showed increased viscosity at higher hematocrits (50-60%) compared to experimental findings.
Conclusions:
- Spaceflight-induced reduction in hematocrit may lower blood viscosity.
- This mechanism could optimize hematocrit levels for tissue oxygen delivery.
- The study highlights the complex interplay between hematocrit and viscosity in altered gravity environments.