Document Detail

Oxygen transport in rest-work transition illustrates new functions for myoglobin.
MedLine Citation:
PMID:  4003568     Owner:  NLM     Status:  MEDLINE    
Myoglobin (Mb) saturation was measured spectroscopically in 1,950 randomly selected cells from dog gracilis muscles frozen in situ during the transition from rest to steady twitch contraction at approximately 70% maximum rate of O2 consumption (VO2max). Measurements were made at the center of muscle-cell profiles in cross section, with spatial resolution approximately 5 X 5 X 3 micron. PO2 was calculated from saturation by use of the oxymyoglobin dissociation curve. Flow increased more rapidly than VO2 (half-times 5 and 14 s, respectively). Mb saturation changed little through 15 s. Saturation was lowest at 30 s and rose somewhat between 30 s and steady state. The lowest intracellular PO2 at any time or location was 1.5 Torr, and only 5% of loci were below 2 Torr. Since 1.5 Torr is about 10 times the minimum PO2 required for the observed VO2 (Connett et al. An upper bound on the minimum PO2 for O2 consumption in red muscle in vivo. Adv. Exp. Med. Biol. In press.), neither anoxia nor hypoxia was present. The observed fall in saturation and intracellular PO2 during exercise permits Mb to 1) promote transcapillary O2 flux, 2) facilitate intracellular O2 diffusion, 3) minimize convective and diffusive shunting, and 4) buffer intracellular PO2 above the tension that limits cytochrome turnover.
T E Gayeski; R J Connett; C R Honig
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The American journal of physiology     Volume:  248     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1985 Jun 
Date Detail:
Created Date:  1985-07-25     Completed Date:  1985-07-25     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  H914-21     Citation Subset:  IM; S    
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MeSH Terms
Biological Transport
Intracellular Fluid / analysis
Muscles / physiology
Myoglobin / physiology*
Oxygen Consumption*
Physical Exertion*
Time Factors
Grant Support
Reg. No./Substance:

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