| Oxygen transport during exercise in large mammals. I. Adaptive variation in oxygen demand. | |
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MedLine Citation:
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PMID: 2793686 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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This study investigated mechanisms used by horses and steers to increase O2 uptake and delivery (VO2) from resting to maximal rates and identified the mechanisms that enable horses to achieve higher maximal rates of O2 consumption (VO2max) than steers. VO2 and circulatory variables were measured while Standardbred trotting horses and steers (450-kg body mass) stood quietly and ran on a treadmill at speeds up to those eliciting VO2max. As VO2 increased in both species, heart rate and circulating hemoglobin (Hb) concentration increased, thereby increasing O2 delivery by the circulation, while cardiac stroke volume remained unchanged. At VO2max arterial PCO2 increased from its resting value in horses but was unchanged in steers, and arterial PO2 decreased in both species. Although the horses hypoventilated and were hypoxemic at VO2max, no significant decrease in arterial Hb saturation occurred. VO2max of the horses was 2.6 times higher than that of the steers and was associated with a 100% larger cardiac output, 100% larger stroke volume, and 40% higher Hb concentration, whereas heart rates at VO2max were identical in the two species. The higher cardiac output of the horses at VO2max resulted from a 1.2-fold higher mean arterial pressure and 1.6-fold lower peripheral tissue resistance (associated with a larger skeletal muscle capillary bed). Both the magnitude of the difference in VO2max between horses and steers and the mechanisms used to achieve it are the same as observed in smaller pairs of mammalian species with large variation in aerobic capacity. |
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Authors:
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J H Jones; K E Longworth; A Lindholm; K E Conley; R H Karas; S R Kayar; C R Taylor |
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Publication Detail:
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Type: Comparative Study; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S. |
Journal Detail:
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Title: Journal of applied physiology (Bethesda, Md. : 1985) Volume: 67 ISSN: 8750-7587 ISO Abbreviation: J. Appl. Physiol. Publication Date: 1989 Aug |
Date Detail:
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Created Date: 1989-11-15 Completed Date: 1989-11-15 Revised Date: 2008-11-21 |
Medline Journal Info:
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Nlm Unique ID: 8502536 Medline TA: J Appl Physiol Country: UNITED STATES |
Other Details:
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Languages: eng Pagination: 862-70 Citation Subset: IM; S |
Affiliation:
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Department of Medicine I, College of Veterinary Medicine, Swedish University of Agricultural Sciences, Uppsala. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Adaptation, Physiological Animals Cardiac Output Cardiac Volume Cattle / physiology* Exercise Test Heart Rate Hemoglobins / analysis Horses / physiology* Oxygen Consumption* Physical Conditioning, Animal Physical Exertion* Respiratory Physiological Phenomena |
| Chemical | |
Reg. No./Substance:
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0/Hemoglobins |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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