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Excessive erythrocytosis does not elevate capillary oxygen delivery in subcutaneous mouse tissue
Thomas Frietsch1, Max Gassmann, Gesine Groth
1Department of Anesthesiology and Critical Care Medicine, Medical Faculty Mannheim of the University of Heidelberg, Germany. bv3@ix.urz.uni-heidelberg.de
Microcirculation (New York, N.Y. : 1994)
|March 17, 2007
Summary
Excessive erythrocytosis in mice increased blood viscosity but did not improve oxygen delivery to capillaries. This suggests high hematocrit may not enhance tissue oxygenation despite increased oxygen-carrying capacity.
Area of Science:
- Physiology
- Hematology
- Microcirculation
Background:
- Acclimatization to low oxygen increases red blood cells (erythrocytes) via erythropoietin.
- Elevated hematocrit from increased erythrocytes raises blood viscosity, potentially impairing microcirculation and tissue oxygenation.
Purpose of the Study:
- To investigate the impact of excessive erythrocytosis on skin oxygen supply using transgenic mice.
- To assess if oxygen-independent, high hematocrit levels affect microcirculatory oxygen distribution.
Main Methods:
- Utilized erythropoietin overexpressing transgenic mice (tg6) with 4-fold higher blood viscosity.
- Employed automated phosphorescence quenching to measure partial oxygen pressure (pO2) in microvessels and tissue.
- Analyzed microvessel diameter, blood oxygen content, hemoglobin's oxygen affinity, and pO2 in arterioles, venules, capillaries, and tissue.
Main Results:
- Transgenic mice exhibited 4-fold higher blood viscosity without altered microvessel diameter.
- Despite similar blood pO2, transgenic animals had doubled oxygen content due to altered hemoglobin-oxygen affinity (decreased 2,3-DPG, increased Hill number).
- Arteriolar and venular pO2 increased in transgenic mice, but capillary and tissue pO2 remained unchanged.
Conclusions:
- Excessive erythrocytosis, even with enhanced oxygen-carrying capacity, does not improve capillary oxygen delivery.
- High hematocrit levels may not translate to better tissue oxygenation due to microcirculatory limitations.
