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Effects of anoxia on kinetics of (/sup 13/N) glutamate and /sup 13/NH/sub 3/ metabolism in rabbit myocardium

Journal Article · · Circ. Res.; (United States)
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Positron emission tomography is a unique noninvasive imaging technique that provides cross-sectional images of radiotracer concentrations in myocardium and permits measurement of blood flow as well as metabolism. Ammonia and glutamate have been labeled with the positron-emitter /sup 13/N (half-life 10 minutes) for use with positron emission tomography as tracers of flow and metabolism, respectively. In order to characterize the fate of these /sup 13/N-labelled compounds in myocardium, isolated rabbit interventricular septa were used to study the kinetics of (/sup 13/N) glutamate ((/sup 13/N)glu) and /sup 13/NH/sub 3/ under aerobic and anoxic conditions. Tissue analyses 6 minutes after injection of a (/sup 13/N)glu bolus into myocardium revealed that 70% of the /sup 13/N-label was present in (/sup 13/N)glu 12%, 11%, and 4% in (/sup 13/N)alanine ((/sup 13/N)ala), (/sup 13/N)aspartate ((/sup 13/N)asp), and (/sup 13/N)glutamine ((/sup 13/N)gln), respectively. The corresponding relative specific activities were 1.0:0.4:0.5:0.01. Anoxia resulted in a significant increase in (/sup 13/N)ala with a reduction in (/sup 13/N)glu. This was consistent with increased pyruvate production due to increased anaerobic glycolysis and transamination of pyruvate with (/sup 13/N)glu to yield (/sup 13/N)ala. In support of this, addition of 2 mM pyruvate to the perfusate under control conditions produced a tissue distribution of /sup 13/N similar to that with anoxia. Six minutes after a bolus of /sup 13/NH/sub 3/ during both control and anoxic conditions, 60% of the tissue /sup 13/N-label was in (/sup 13/N)gln with no detectable amounts in other amino acids. The rest of the /sup 13/N-label was in /sup 13/NH/sub 3/. Time-activity curve analyses demonstrated that anoxia significantly reduced the tissue retention of /sup 13/N-label from /sup 13/NH/sub 3/ but not from (/sup 13/N)glu.

Research Organization:
Univ. of California, Los Angeles
OSTI ID:
6068522
Journal Information:
Circ. Res.; (United States), Journal Name: Circ. Res.; (United States) Vol. 60:4; ISSN CIRUA
Country of Publication:
United States
Language:
English

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Related Subjects

550601 -- Medicine-- Unsealed Radionuclides in Diagnostics
560300* -- Chemicals Metabolism & Toxicology
62 RADIOLOGY AND NUCLEAR MEDICINE
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
AMINO ACIDS
AMMONIA
ANIMALS
ANOXIA
BETA DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL EFFECTS
BLOOD FLOW
BODY
CARBOXYLIC ACIDS
CARDIOVASCULAR SYSTEM
COMPUTERIZED TOMOGRAPHY
DIAGNOSTIC TECHNIQUES
ELECTRON CAPTURE RADIOISOTOPES
GLUTAMIC ACID
HEART
HYDRIDES
HYDROGEN COMPOUNDS
ISOTOPES
KINETICS
LABELLED COMPOUNDS
LIGHT NUCLEI
MAMMALS
METABOLISM
MINUTES LIVING RADIOISOTOPES
MUSCLES
MYOCARDIUM
NITROGEN 13
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NITROGEN ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
RABBITS
RADIOISOTOPES
REACTION KINETICS
RETENTION
TOMOGRAPHY
VERTEBRATES