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Theoretical predictions of end-capillary PO2 in muscles of athletic and nonathletic animals at VO2max.
Abstract: Characterizing the resistances to O2 transport from the erythrocyte to the mitochondrion is important in understanding potential transport limitations. A steady-state model of this process was developed to predict the minimum (critical) end-capillary PO2 required to prevent hypoxia at maximal O2 consumption (VO2max) in a circular region of tissue surrounding the venular end of a capillary. Capillary density was used as a measure of O2 delivery, and mitochondrial density was used as a measure of O2 consumption. The effects of oxyhemoglobin dissociation kinetics and diffusion facilitation by hemoglobin in the erythrocytes and facilitation by myoglobin in the tissue were taken into account. Calculations made for selected skeletal muscles, diaphragm, and myocardium in three adaptive animal pairs (dog and goat, horse and cow, and pony and calf) yielded values of end-capillary PO2 that were consistent with measured values of mixed venous PO2 in maximally working animals. Values of end-capillary PO2 were found to be uncorrelated with values of VO2max in different muscles. No significant difference in end-capillary PO2 was found between similar muscles of athletic versus nonathletic animals. Predicted intracapillary O2 transport resistance ranged from 18 to 54% of the total transport resistance in the O2 pathway. Further investigation is required to explore the extent to which spatial and temporal heterogeneities in O2 delivery and consumption play a role in O2 transport.
Publication Date: 1996-08-01 PubMed ID: 8770116DOI: 10.1152/ajpheart.1996.271.2.H721Google 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
- U.S. Gov't
- P.H.S.
- Review
Summary
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The research article discusses a theoretical model created to predict the minimum end-capillary oxygen level necessary to prevent hypoxia (oxygen deficiency) in tissues during maximum oxygen consumption in athletic and non-athletic animals. This model considered variables such as oxygen delivery, oxygen consumption, and the role of certain proteins in oxygen transportation. The results found uniformity in oxygen level across different types of muscles as well as between athletic and non-athletic animals.
Understanding Oxygen Transport and Consumption
- The study focuses on understanding the mechanisms of oxygen transport from the erythrocyte (a cell that contains hemoglobin and is responsible for transporting oxygen in the blood) to the mitochondrion (an organelle found in cells that produces energy in the form of ATP – adenosine triphosphate).
- This understanding is key to identifying potential limitations in oxygen transport in the body. A theoretical model was thus proposed to help in understanding this process more systematically.
Theoretical Model for Oxygen Consumption
- A steady-state model was developed to predict the minimum (critical) end-capillary oxygen level required to prevent hypoxia (oxygen deficiency) when the body undergoes maximum oxygen consumption (VO2max).
- The model represents a circular body tissue section at the venular end of a capillary. Variables involved in the model include capillary density, representing oxygen delivery, and mitochondrial density, representing oxygen consumption
Consideration for Proteins in Oxygen Transportation
- The model also considers the effects of oxygen dissociation rate of hemoglobin (a protein in red blood cells that carries oxygen) and diffusion facilitation by hemoglobin in erythrocytes and myoglobin (an oxygen-storing protein) in body tissues.
Findings and Results
- Calculations were made for selected muscles in various animal pairs like dogs and goats, horses and cows, and ponies and calves. The results showed consistency with in vivo measurements in maximally working animals.
- The findings showed that end-capillary oxygen levels were not correlated with values of maximum oxygen consumption in different muscles. Additionally, no significant difference was observed between muscles of athletic versus non-athletic animals.
- The predicted resistance in oxygen transportation within the capillary varied from 18 to 54% of the total transport resistance in the oxygen pathway.
Further Research Direction
- In light of the findings, further research needs to be conducted. An aspect that needs to be studied includes how variations in oxygen delivery and consumption temporally or spatially in the body affect oxygen transport.
Cite This Article
APA
Roy TK, Popel AS.
(1996).
Theoretical predictions of end-capillary PO2 in muscles of athletic and nonathletic animals at VO2max.
Am J Physiol, 271(2 Pt 2), H721-H737.
https://doi.org/10.1152/ajpheart.1996.271.2.H721 Publication
Researcher Affiliations
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
MeSH Terms
- Animals
- Capillaries
- Cattle
- Diffusion
- Dogs
- Female
- Forecasting
- Goats
- Horses
- Models, Cardiovascular
- Muscles / blood supply
- Oxygen / blood
- Oxygen / metabolism
- Oxygen Consumption
- Partial Pressure
- Physical Conditioning, Animal
- Sensitivity and Specificity
Grant Funding
- HL-18292 / NHLBI NIH HHS
Citations
This article has been cited 9 times.- Poole DC, Musch TI. Capillary-Mitochondrial Oxygen Transport in Muscle: Paradigm Shifts. Function (Oxf) 2023;4(3):zqad013.
- Poole DC, Musch TI, Colburn TD. Oxygen flux from capillary to mitochondria: integration of contemporary discoveries. Eur J Appl Physiol 2022 Jan;122(1):7-28.
- Skattebo Ø, Calbet JAL, Rud B, Capelli C, Hallén J. Contribution of oxygen extraction fraction to maximal oxygen uptake in healthy young men. Acta Physiol (Oxf) 2020 Oct;230(2):e13486.
- Secomb TW. Krogh-cylinder and infinite-domain models for washout of an inert diffusible solute from tissue. Microcirculation 2015 Jan;22(1):91-8.
- Charton A, Péronnet F, Doutreleau S, Lonsdorfer E, Klein A, Jimenez L, Geny B, Diemunsch P, Richard R. Effect of administration of water enriched in O2 by injection or electrolysis on transcutaneous oxygen pressure in anesthetized pigs. Drug Des Devel Ther 2014;8:1161-7.
- Liu G, Mac Gabhann F, Popel AS. Effects of fiber type and size on the heterogeneity of oxygen distribution in exercising skeletal muscle. PLoS One 2012;7(9):e44375.
- Dasika SK, Kinsey ST, Locke BR. Facilitated diffusion of myoglobin and creatine kinase and reaction-diffusion constraints of aerobic metabolism under steady-state conditions in skeletal muscle. Biotechnol Bioeng 2012 Feb;109(2):545-58.
- Liu G, Qutub AA, Vempati P, Mac Gabhann F, Popel AS. Module-based multiscale simulation of angiogenesis in skeletal muscle. Theor Biol Med Model 2011 Apr 4;8:6.
- Laghi F, Shaikh H, Caccani N. Basing intubation of acutely hypoxemic patients on physiologic principles. Ann Intensive Care 2024 Jun 12;14(1):86.
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