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Influence of increased metabolic rate on [^(13)C]bicarbonate washout kinetics

Barstow, Thomas J. and Cooper, Dan M. and Sobel, Eric M. and Landaw, Elliot M. and Epstein, Sam (1990) Influence of increased metabolic rate on [^(13)C]bicarbonate washout kinetics. American Journal of Physiology, 259 (1). R163-R171. ISSN 0002-9513.

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The effect of changes in metabolic rate on the dynamics of CO_2 exchange among its various compartments in the human body is not well understood. We examined CO_2 dynamics in six healthy male subjects using an intravenous bolus of [^(13)C]bicarbonate. Subjects were studied while resting, during light exercise [50% of the lactate threshold (LT), 3-4 times resting O_2 uptake (V_(O_2))], and during moderate exercise (95% of the LT, 6 times resting V_(O_2)). The sum of three exponential terms well described the washout of ^(13)CO_2 in exhaled breath both at rest and during each exercise level despite substantial increases in metabolic rate accompanying the exercise studies. Average recovery of ^(13)C label rose from 67% during rest to 80% during light and moderate exercise (P less than 0.01). The estimate of CO_2 elimination (V_(CO_2)) calculated from the washout parameters and corrected for recovery was in very good agreement with the V_(CO_2) directly measured simultaneously breath by breath (r = 0.993, SE for V_(CO_2) = 0.079 l/min). By use of a three-compartment mammillary model, the quantity of CO_2 in the central pool (Q_1) doubled from rest to light exercise (233 +/- 60 to 479 +/- 76 mmol, P less than 0.01) but did not change further with moderate exercise (458 +/- 74 mmol). Rate constants for exchange between pools and for irreversible loss from the system tended to increase with metabolic rate, but there was large variation in the responses. We conclude that the compartmental dynamics of CO_2 transport and storage are very sensitive to changes in metabolic rate induced by exercise.

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Alternate Title:Influence of increased metabolic rate on [13C]bicarbonate washout kinetics
Additional Information:© 1990 American Physiological Society. Received 8 February 1989; accepted in final form 6 March 1990. We thank Joe Ruth and Eleanor Dent for analysis of the ^(13)CO_2 samples. This work was supported in part by National Heart, Lung, and Blood Institute Grant HL-11907. T. J. Barstow was supported by National Institutes of Health Grant T32-DK-07461-04. E. M. Landaw was supported in part by National Cancer Institute Grant CA-16042. D. M. Cooper is the recipient of the Clinician Scientist Award of the American Heart Association, Greater Los Angeles Affiliate, and the Career Investigator Award of the American and California Lung Associations.
Funding AgencyGrant Number
National Heart, Lung, and Blood Institute GrantHL-11907
Clinician Scientist Award, American Heart Association, Greater Los Angeles AffiliateUNSPECIFIED
Career Investigator, American and California Lung AssociationsUNSPECIFIED
Subject Keywords:stable isotope; carbon dioxide transport; mammillary model; compartmental analysis; gas exchange
Issue or Number:1
Record Number:CaltechAUTHORS:20140717-073123393
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Official Citation:Influence of increased metabolic rate on [13C]bicarbonate washout kinetics T. J. Barstow, D. M. Cooper, E. M. Sobel, E. M. Landaw, S. Epstein July 1, 1990: R163-R171
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:47280
Deposited By: Ruth Sustaita
Deposited On:17 Jul 2014 18:31
Last Modified:03 Oct 2019 06:52

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