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Effect of increased metabolic rate on oxygen isotopic fractionation

Zanconato, Stefania and Cooper, Dan M. and Armon, Yaacov and Epstein, Samuel (1992) Effect of increased metabolic rate on oxygen isotopic fractionation. Respiration Physiology, 89 (3). pp. 319-327. ISSN 0034-5687. doi:10.1016/0034-5687(92)90090-J.

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^(16)O^(16)O is preferentially used over ^(18)O^(16)O (a stable isotope of oxygen comprising about 0.2% of atmospheric O_2) as oxygen is consumed during respiration in humans (Epstein and Zeiri, 1988, Proc. Natl. Acad. Sci. USA 85: 1727–1731). To test the hypothesis that oxygen isotopic fractionation is related to the metabolic rate, 8 healthy adults performed 5 min of constant work rate cycle ergometer exercise below and above their anaerobic threshold. Moreover, 3 subjects performed an incremental exercise to the limit of tolerance. Oxygen uptake (V̇_(O2)) was measured breath by breath. Samples of the exhaled breath for oxygen isotope measurement were obtained at rest and at various times during exercise and recovery. Oxygen isotopic fractionation was determined by isotope ratio mass spectrometry and calculated as the ratio of the degree of fractionation to the oxygen consumed in the breath sample (Z value). For the constant work rate protocol, both low and high intensity exercise resulted in a significant decrease in Z compared to the rest values (P < 0.01). However, for the high intensity exercise the reduction in fractionation was greater compared to the low intensity protocol (P < 0.05). For the incremental test, there was a significant negative correlation between oxygen isotopic fractionation and V̇_(O2) expressed as percent of the maximal oxygen uptake (r = −0.91, P < 0.0001). These data suggest that during exercise low-fractionating processes become more important as limiting steps for O_2 transport.

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Additional Information:© 1992 Elsevier Science Publishers B.V. All rights reserved. Accepted 21 April 1992. This work was supported by US PHS HL4053. Stefania Zanconato is a Research Fellow of the American Heart Association, Greater Los Angeles Affiliate. Dan M. Cooper is the recipient of the Career Investigator Award, American Lung Association. Yaacov Armon is a Research Fellow of the Joseph Drown Foundation.
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United States Public Health Service (USPHS)HL4053
Subject Keywords: Exercise, O2 fractionation; Isotope, O2 fractionation, exercise; Mammals, humans
Issue or Number:3
Record Number:CaltechAUTHORS:20131112-114902531
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Official Citation:Stefania Zanconato, Dan M. Cooper, Yaacov Armon, Samuel Epstein, Effect of increased metabolic rate on oxygen isotopic fractionation, Respiration Physiology, Volume 89, Issue 3, September 1992, Pages 319-327, ISSN 0034-5687, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42391
Deposited By: Ruth Sustaita
Deposited On:12 Nov 2013 21:53
Last Modified:10 Nov 2021 16:22

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