Sample site selection for tracer studies applying a unidirectional circulatory approach
The optimal arterial or venous sites for infusion and sampling during isotopic tracer studies have not been established. This study determined the relationship of plasma and tissue enrichment (E) when isotopes were infused in an artery and sampled from a vein (av mode) or infused in a vein and sampled from an artery (va mode). Adult dogs were given primed constant infusions of (3-/sup 13/C)lactate, (1-/sup 13/C)leucine, and /sup 14/C-labeled bicarbonate. Simultaneous samples were drawn from the vena cava, aortic arch, and breath. Tissue samples were removed from skeletal muscle, liver, kidney, and gut. Breath samples were analyzed for /sup 14/CO/sub 2/ by liquid scintillation counting and plasma isotopic enrichments of (/sup 13/C)lactate, (/sup 13/C)leucine, and alpha-(/sup 13/C)ketoisocaproate (KIC) were determined by gas chromatography-mass spectrometry. By using the va mode, the plasma E for lactate and leucine were 30-40% above tissue E. The av mode provided an accurate reflection of tissue E for lactate, which equilibrates rapidly with tissues, and a reasonable estimate for leucine, which exchanges more slowly. The isotopic enrichment of plasma KIC more directly reflected tissue leucine E than did plasma leucine E, and KIC enrichment was insensitive to sampling site. We also evaluated theoretically a circulatory model that predicts venous isotopic enrichments when the va mode is used. We conclude that the av mode is optimal but that the problems arising from use of the va mode can be overcome by use of a metabolic product (i.e., KIC) or by calculation of venous specific activity with our circulatory mode.
- Research Organization:
- Univ. of Illinois, Urbana
- OSTI ID:
- 6243960
- Journal Information:
- Am. J. Physiol.; (United States), Vol. 253
- Country of Publication:
- United States
- Language:
- English
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BLOOD CIRCULATION
TRACER TECHNIQUES
CARBON 13
INFUSION
CARBON 14 COMPOUNDS
ACETATES
ACID CARBONATES
ARTERIES
BIOLOGICAL MODELS
BLOOD PLASMA
CARBON DIOXIDE
DOGS
GAS CHROMATOGRAPHY
INTESTINES
KETO ACIDS
KIDNEYS
LEUCINE
LIVER
MASS SPECTROSCOPY
MUSCLES
RESPIRATION
SCINTILLATION COUNTING
SODIUM
VEINS
ALKALI METALS
AMINO ACIDS
ANIMALS
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BLOOD
BLOOD VESSELS
BODY
BODY FLUIDS
CARBON COMPOUNDS
CARBON ISOTOPES
CARBON OXIDES
CARBOXYLIC ACID SALTS
CARBOXYLIC ACIDS
CARDIOVASCULAR SYSTEM
CHALCOGENIDES
CHROMATOGRAPHY
COUNTING TECHNIQUES
DIGESTIVE SYSTEM
ELEMENTS
EVEN-ODD NUCLEI
GASTROINTESTINAL TRACT
GLANDS
INTAKE
ISOTOPE APPLICATIONS
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METALS
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
OXIDES
OXYGEN COMPOUNDS
SEPARATION PROCESSES
SPECTROSCOPY
STABLE ISOTOPES
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551001* - Physiological Systems- Tracer Techniques