Metabolic fate of L-(N-13) glutamate in normal isolated myocardium

Conference · Sun Jan 01 04:00:00 EST 1984 · J. Nucl. Med.; (United States)

OSTI ID:6845471

Keen, R E; Krivokapich, J; Barrio, J R; Douglas, A; Wittmer, S; Shine, K; Phelps, M E

In the present work nitrogen flux of an amino acid in myocardium is followed via arterial bolus injection of non-carrier added L-(N-13)glutamate (N-13 GLU) into the isolated rabbit septa. Incorporation of nitrogen-13 into (N-13)aspartate (N-13 ASP)(16%) and (N-13)alanine (N-13 ALA)(14%) predominates over (N-13)glutamine (N-13 GLN) (3.2%) as determined by reversed phase HPLC in normal septa 6 min after bolus injection. No N-13 ammonia or N-13 urea is detected. Introduction of the transaminase inhibitor aminooxyacetate (AOA, 2 nM) into perfusate completely blocked transaminase reaction and increased N-13 GLN (7.3%) and free N-13 ammonia (4.0%), probably resulting from glutamate dehydrogenase reaction. Inclusion of 2mM pyruvate in the perfusate resulted in 3 fold increase in N-13 ALA (44%), slight increase in N-13 GLN (5.0%) and significant decrease in N-13 ASP. Addition of 2mM AOA in the presence of pyruvate blocked production of N-13 ASP and N-13 ALA, and increased N-13 GLN slightly (6.0%). All studies had similar residual fractions (50%) except AOA treated septa (23%) indicating decreased metabolic trapping of the N-13 label. In conclusion, nitrogen-13 distribution in tissue is primarily governed by glutamate interaction with transaminases. Although the Michaelis constants of glutamate for GOT (Km = 4 nM, pig heart), GPT (Km = 8.1 mM, beef heart) and glutamine synthetase (Km = 2.5 mM, ovine brain) are similar, the transaminases play a predominant role because of their great abundance in myocardial tissue.

• Research Organization: UCLA School of Medicine, Los Angeles, CA
• OSTI ID: 6845471
• Report Number(s): CONF-840619-
• Conference Information: Journal Name: J. Nucl. Med.; (United States) Journal Volume: 25:5
• Country of Publication: United States
• Language: English

Related Subjects

550501* -- Metabolism-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALANINES
AMIDES
AMINO ACIDS
AMINOTRANSFERASES
ANIMALS
ASPARTIC ACID
BETA DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL FUNCTIONS
BIOLOGICAL PATHWAYS
BODY
CARBOXYLIC ACIDS
CARDIOVASCULAR SYSTEM
CHROMATOGRAPHY
DIAGNOSTIC USES
ELECTRON CAPTURE RADIOISOTOPES
ENZYME INHIBITORS
ENZYMES
FUNCTIONS
GLUTAMIC ACID
GLUTAMINE
HEART
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGHT NUCLEI
LIQUID COLUMN CHROMATOGRAPHY
MAMMALS
METABOLISM
MINUTES LIVING RADIOISOTOPES
MUSCLES
MYOCARDIUM
NITROGEN 13
NITROGEN ISOTOPES
NITROGEN TRANSFERASES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
RABBITS
RADIOISOTOPES
REACTION KINETICS
SEPARATION PROCESSES
TRACER TECHNIQUES
TRANSFERASES
USES
VERTEBRATES