CO/sub 2/ production in animals: analysis of potential errors in the doubly labeled water method. [/sup 3/H and /sup 18/O]

Technical Report · Thu Mar 01 00:00:00 EST 1979

DOI:https://doi.org/10.2172/6295032· OSTI ID:6295032

Nagy, K A

Laboratory validation studies indicate that doubly labeled water (/sup 3/HH/sup 18/O and /sup 2/HH/sup 18/O) measurements of CO/sub 2/ production are accurate to within +-9% in nine species of mammals and reptiles, a bird, and an insect. However, in field studies, errors can be much larger under certain circumstances. Isotopic fraction of labeled water can cause large errors in animals whose evaporative water loss comprises a major proportion of total water efflux. Input of CO/sub 2/ across lungs and skin caused errors exceeding +80% in kangaroo rats exposed to air containing 3.4% unlabeled CO/sub 2/. Analytical errors of +-1% in isotope concentrations can cause calculated rates of CO/sub 2/ production to contain errors exceeding +-70% in some circumstances. These occur: 1) when little decline in isotope concentractions has occured during the measurement period; 2) when final isotope concentrations closely approach background levels; and 3) when the rate of water flux in an animal is high relative to its rate of CO/sub 2/ production. The following sources of error are probably negligible in most situations: 1) use of an inappropriate equation for calculating CO/sub 2/ production, 2) variations in rates of water or CO/sub 2/ flux through time, 3) use of H/sub 2/O-18 dilution space as a measure of body water volume, 4) exchange of 0-18 between water and nonaqueous compounds in animals (including excrement), 5) incomplete mixing of isotopes in the animal, and 6) input of unlabeled water via lungs and skin. Errors in field measurements of CO/sub 2/ production can be reduced to acceptable levels (< 10%) by appropriate selection of study subjects and recapture intervals.

• Research Organization: Univ. of California, Los Angeles, CA (United States)
• DOE Contract Number: EY-76-C-03-0012
• OSTI ID: 6295032
• Report Number(s): UCLA-12-1189; TRN: 79-009436
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ANIMALS
RESPIRATION
CARBON DIOXIDE
RADIOASSAY
ERRORS
TRACER TECHNIQUES
WATER
METABOLISM
DEUTERIUM COMPOUNDS
DOUBLE LABELLING
HEAVY WATER
LABELLED COMPOUNDS
OXYGEN 18
TRITIUM COMPOUNDS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
EVEN-EVEN NUCLEI
HYDROGEN COMPOUNDS
ISOTOPE APPLICATIONS
ISOTOPES
LABELLING
LIGHT NUCLEI
NUCLEI
OXIDES
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
STABLE ISOTOPES
551001* - Physiological Systems- Tracer Techniques
550501 - Metabolism- Tracer Techniques
550201 - Biochemistry- Tracer Techniques