Limitations of tracer oxygen uptake in the canine coronary circulation
Theoretical models of oxygen transport in the myocardium have failed to account for low average tissue pO/sub 2/ relative to to coronary sinus pO/sub 2/, measured with pO/sub 2/ electrodes and myoglobin saturation, and for hypoxic contractile failure at relatively high coronary sinus pO/sub 2/ levels. These findings could be explained by either arteriovenous diffusional shunting or a limiting rate of transfer of oxygen from blood to tissue, or both. To gain new insights, the authors performed multiple indicator dilution tracer experiments across the coronary circulation in the dog, with /sup 18/O/sub 2/ as the oxygen tracer and /sup 51/Cr-labeled red cells as the reference tracer for oxygen. /sup 125/I-Albumin and /sup 22/Na+ were included to provide the relative plasma flow rate. The tracer oxygen outflow curve consisted of a large early peak related to its reference red cell curve. No tracer emerged before the labeled red cells. The downslope, which contains the returning component of the tracer curve, decreased less steeply when oxygen consumption was reduced by propranolol. Fitting the tracer oxygen outflow curve with a distributed model including irreversible sequestration behind a resistance gave a transfer rate constant which was relatively small, and a relatively large rate constant for sequestration. Relative oxygen consumption (estimated from the arteriovenous difference) correlated closely with the rate constant for sequestration. Estimated average tissue oxygen concentrations were of the order of one-third blood concentration.
- Research Organization:
- McGill Univ. Medical Clinic, Quebec, Canada
- OSTI ID:
- 5708246
- Journal Information:
- Circ. Res.; (United States), Vol. 56:1
- Country of Publication:
- United States
- Language:
- English
Similar Records
Noninvasive assessment of canine myocardial oxidative metabolism with carbon-11 acetate and positron emission tomography
Validation of (1- sup 11 C)acetate as a tracer for noninvasive assessment of oxidative metabolism with positron emission tomography in normal, ischemic, postischemic, and hyperemic canine myocardium
Related Subjects
CORONARIES
BLOOD CIRCULATION
OXYGEN
MEMBRANE TRANSPORT
ALBUMINS
BLOOD FLOW
CATIONS
CHROMIUM 51
DOGS
ELECTRODES
ERYTHROCYTES
IODINE 125
LABELLED COMPOUNDS
MATHEMATICAL MODELS
MYOCARDIUM
MYOGLOBIN
OXYGEN 18
PERMEABILITY
SODIUM COMPOUNDS
TRACER TECHNIQUES
UPTAKE
ALKALI METAL COMPOUNDS
ANIMALS
ARTERIES
BETA DECAY RADIOISOTOPES
BIOLOGICAL MATERIALS
BLOOD
BLOOD CELLS
BLOOD VESSELS
BODY
BODY FLUIDS
CARBOXYLIC ACIDS
CARDIOVASCULAR SYSTEM
CHARGED PARTICLES
CHROMIUM ISOTOPES
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
ELEMENTS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
GLOBIN
HEART
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
IONS
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
MAMMALS
MATERIALS
MUSCLES
NONMETALS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
OXYGEN ISOTOPES
PIGMENTS
PORPHYRINS
PROTEINS
RADIOISOTOPES
STABLE ISOTOPES
VERTEBRATES
551001* - Physiological Systems- Tracer Techniques