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Rheological characteristics of horse blood: significance during exercise.
Abstract: When horses maximally exercise, splenic contraction and fluid movement out of the vascular compartment greatly increase the hematocrit (up to 0.70). We studied the in vitro rheological characteristics of blood from Thoroughbreds and Quarter Horses to determine the interaction of hematocrit and shear rate on apparent viscosity. We also compared the rheological characteristics of the blood before and after horses received furosemide, a drug commonly used to prevent exercise-induced pulmonary hemorrhage. Although the apparent viscosity of blood with a high hematocrit was high at low shear rates, it rapidly decreased as the shear rate increased and appeared to continue to decrease at shear rates above 450 sec-1, which was the limit of our measurement capability. Furosemide had no detectable influence on the measured in vitro rheological characteristics of the blood at any hematocrit or shear rate studied. We postulate that during exercise, when shear rates in the circulation are high, apparent viscosity at high hematocrit may approach values similar to those that occur during rest when both hematocrit and shear rates are lower. Consequently, the shear-dependent properties of blood may create a homeostasis of viscosity in vivo during exercise so that high viscosity is not a major factor contributing to vascular resistance.
Publication Date: 1993-12-01 PubMed ID: 8108610DOI: 10.1016/0034-5687(93)90027-8Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- P.H.S.
Summary
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This research investigates how the viscosity of horse blood changes during intense exercise and the effects of a common drug, furosemide. The study suggests that despite an initial high viscosity when hematocrit levels (the proportion of blood volume occupied by red blood cells) increase, shear rates (rate of change of velocity at which one layer of fluid passes over an adjacent layer) in circulation reduce this viscosity to resting levels during exercise, maintaining stable vascular resistance.
Rheological Characteristics of Horse Blood
- The research primarily focused on understanding the rheological (flow characteristics) of horse blood, particularly Thoroughbreds and Quarter Horses, during maximal exertion.
- The scientists noticed that during intense exercise, the contraction of the spleen and movement of fluids from the blood vessels increase hematocrit (the proportion of blood volume filled with red blood cells) levels up to 0.70.
- The researchers aimed to decipher the relationship between hematocrit and shear rate (the difference in the velocity of adjacent layers of fluid) on the apparent viscosity (measured resistance to flow under specific conditions) of the blood.
Impact of Furosemide on Horse Blood
- A secondary objective of the research was to analyze the effect of furosemide, a diuretic commonly used in equine medicine to prevent exercise-induced pulmonary hemorrhage (bleeding in the lungs due to overexertion).
- In this study, the effect of furosemide on the flow properties of horse blood was examined before and after the drug administration.
- The results showed no noticeable impact of furosemide on the blood’s rheological characteristics at any hematocrit or shear rate studied.
Findings on Apparent Viscosity and Shear Rate in Horse Blood
- Notably, the researchers found that while the blood’s apparent viscosity was high at low shear rates when hematocrit levels were elevated, it decreased rapidly as the shear rate increased.
- The decrease in apparent viscosity at high shear rates continued even above 450 sec-1, the limit of the study’s measurement ability.
- This suggests that during exercise, the blood’s apparent viscosity could reach values similar to those at rest when both hematocrit and shear rates are lower.
Implications of the Study
- The results suggest that the blood’s shear-dependent properties during exercise could establish a viscosity homeostasis (stable state), meaning that high viscosity does not significantly contribute to vascular resistance (the resistance that must be overcome to push blood through the circulatory system).
- This implies that despite increases in hematocrit levels during exertion, the body’s mechanisms adjust to maintain a stable blood flow and resist any negative effects of high viscosity.
Cite This Article
APA
Fedde MR, Wood SC.
(1993).
Rheological characteristics of horse blood: significance during exercise.
Respir Physiol, 94(3), 323-335.
https://doi.org/10.1016/0034-5687(93)90027-8 Publication
Researcher Affiliations
- Department of Anatomy and Physiology, Kansas State University, Manhattan 66506.
MeSH Terms
- Animals
- Blood Viscosity / drug effects
- Blood Viscosity / physiology
- Furosemide / pharmacology
- Hematocrit
- Hemoglobins / metabolism
- Horses / blood
- In Vitro Techniques
- Physical Exertion / physiology
- Rheology
- Running / physiology
Grant Funding
- HL-40537 / NHLBI NIH HHS
Citations
This article has been cited 5 times.- Storz JF, Cheviron ZA. Physiological Genomics of Adaptation to High-Altitude Hypoxia. Annu Rev Anim Biosci 2021 Feb 16;9:149-171.
- Windberger U, Auer R, Seltenhammer M, Mach G, Skidmore JA. Near-Newtonian Blood Behavior - Is It Good to Be a Camel?. Front Physiol 2019;10:906.
- Schuler B, Arras M, Keller S, Rettich A, Lundby C, Vogel J, Gassmann M. Optimal hematocrit for maximal exercise performance in acute and chronic erythropoietin-treated mice. Proc Natl Acad Sci U S A 2010 Jan 5;107(1):419-23.
- Vengust M, Staempfli H, Viel L, Heigenhauser G. Transvascular fluid flux from the pulmonary vasculature at rest and during exercise in horses. J Physiol 2006 Jan 15;570(Pt 2):397-405.
- Piccione G, Arfuso F, Giudice E, Aragona F, Pugliatti P, Panzera MF, Zumbo A, Monteverde V, Bartolo V, Barbera A, Giannetto C. Dynamic Adaptation of Hematological Parameters, Albumin, and Non-Esterified Fatty Acids in Saddlebred and Standardbred Horses During Exercise. Animals (Basel) 2025 Jan 21;15(3).
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