Oxygen transport during exercise in large mammals. II. Oxygen uptake by the pulmonary gas exchanger.
Abstract: Because the maximal rate of O2 consumption (VO2max) of the horse is 2.6 times larger than that of steers of equal size, we wondered whether their pulmonary gas exchanger is proportionately larger. Three Standardbred racehorses [body mass (Mb) = 447 kg] and three domestic steers (Mb = 474 kg) whose cardiovascular function at VO2max had been thoroughly studied (Jones et al. J. Appl. Physiol. 67: 862-870, 1989) were used to study their lungs by morphometry. The basic morphometric parameters were similar in both species. The nearly 2 times larger lung volumes of the horses caused the gas exchange surfaces and capillary blood volume to be 1.6 to 1.8 times larger. Morphometric pulmonary diffusing capacity was 2 times larger in the horse than in the steer; the 2.6-fold greater rate of O2 uptake thus required the alveolar-capillary PO2 difference to be 1.3 times larger in the horse than in the steer. Combining physiological and morphometric data, we calculated capillary transit time at VO2max to be 0.4-0.5 s. Bohr integration showed capillary blood to be equilibrated with alveolar air after 75 and 58% of transit time in horses and steers, respectively; horses maintain a smaller degree of redundancy in their pulmonary gas exchanger.
Publication Date: 1989-08-01 PubMed ID: 2793687DOI: 10.1152/jappl.1989.67.2.871Google Scholar: Lookup
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- Comparative Study
- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- Non-P.H.S.
Summary
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The researchers compared the lung size and oxygen uptake differences between horses and steers during maximum physical exertion. They found that although both animals are of similar size, horses consume more oxygen and have larger lungs. This implies that horses’ lung design is more efficient in enabling higher oxygen uptake compared to steers.
Study Participants
- The experiment involved three standardbred racehorses and three domestic steers. The horses and steers were chosen because their oxygen consumption rates under maximal exertion conditions were previously studied.
Morphometric Analysis
- Morphometry, which is the quantitative analysis of form, was used to study the lungs of the subjects. It revealed that the basic parameters of the lung structures were similar for both species.
Lung Capacity and Diffusion
- Despite the similar basic morphometric parameters, horses exhibited nearly double the lung volumes of steers, resulting in gas exchange surfaces and capillary blood volumes being 1.6 to 1.8 times larger.
- Pulmonary diffusing capacity, which measures the ability of the lungs to transfer gas from inhaled air to the red blood cells, was found to be twice as large in horses than in steers.
Oxygen Uptake
- The rate of oxygen consumption in horses was 2.6 times greater than in steers. This necessitated a larger alveolar-capillary partial pressure difference (measurement of diffusive driving force for oxygen) in horses than in steers.
- At maximum oxygen consumption, the capillary transit time (the duration blood cells remain in the capillaries and exchange gases) was estimated to be between 0.4 and 0.5 seconds.
Gas Exchange Efficiency
- Using Bohr integration (a calculation method in physiology), it was confirmed that capillary blood was equilibrated (or the gas exchange was completed) after 75% of transit time in horses and 58% in steers.
- Therefore, horses maintain a smaller degree of redundancy in their pulmonary gas exchanger. This means that horses’ lungs have less spare capacity for gas exchange under maximal exertion, which could explain their greater efficiency.
Cite This Article
APA
Constantinopol M, Jones JH, Weibel ER, Taylor CR, Lindholm A, Karas RH.
(1989).
Oxygen transport during exercise in large mammals. II. Oxygen uptake by the pulmonary gas exchanger.
J Appl Physiol (1985), 67(2), 871-878.
https://doi.org/10.1152/jappl.1989.67.2.871 Publication
Researcher Affiliations
- Department of Anatomy, University of Berne, Switzerland.
MeSH Terms
- Animals
- Cattle / physiology
- Exercise Test
- Horses / physiology
- Lung / ultrastructure
- Lung Volume Measurements
- Oxygen Consumption
- Physical Exertion
- Pulmonary Alveoli / blood supply
- Pulmonary Circulation
- Pulmonary Gas Exchange
- Respiratory Physiological Phenomena
Citations
This article has been cited 9 times.- Ferretti G, Fagoni N, Taboni A, Vinetti G, di Prampero PE. A century of exercise physiology: key concepts on coupling respiratory oxygen flow to muscle energy demand during exercise. Eur J Appl Physiol 2022 Jun;122(6):1317-1365.
- Tabozzi SA, Stancari G, Zucca E, Tajoli M, Stucchi L, Lafortuna CL, Ferrucci F. Variation of skeletal muscle ultrasound imaging intensity in horses after treadmill exercise: a proof of concept for glycogen content estimation. BMC Vet Res 2021 Mar 16;17(1):121.
- Srikanth K, Kim NY, Park W, Kim JM, Kim KD, Lee KT, Son JH, Chai HH, Choi JW, Jang GW, Kim H, Ryu YC, Nam JW, Park JE, Kim JM, Lim D. Comprehensive genome and transcriptome analyses reveal genetic relationship, selection signature, and transcriptome landscape of small-sized Korean native Jeju horse. Sci Rep 2019 Nov 13;9(1):16672.
- Hsia CC, Hyde DM, Weibel ER. Lung Structure and the Intrinsic Challenges of Gas Exchange. Compr Physiol 2016 Mar 15;6(2):827-95.
- Crocker GH, Jones JH. Hypoxia and CO alter O2 extraction but not peripheral diffusing capacity during maximal aerobic exercise. Eur J Appl Physiol 2014 Apr;114(4):837-45.
- Gu J, Orr N, Park SD, Katz LM, Sulimova G, MacHugh DE, Hill EW. A genome scan for positive selection in thoroughbred horses. PLoS One 2009 Jun 2;4(6):e5767.
- Lafortuna CL, Saibene F, Albertini M, Clement MG. The regulation of respiratory resistance in exercising horses. Eur J Appl Physiol 2003 Oct;90(3-4):396-404.
- Sapoval B, Filoche M, Weibel ER. Smaller is better--but not too small: a physical scale for the design of the mammalian pulmonary acinus. Proc Natl Acad Sci U S A 2002 Aug 6;99(16):10411-6.
- Weibel ER, Taylor CR, Hoppeler H. The concept of symmorphosis: a testable hypothesis of structure-function relationship. Proc Natl Acad Sci U S A 1991 Nov 15;88(22):10357-61.
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