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HERO ID
990690
Reference Type
Journal Article
Title
Human (13)N-ammonia PET studies: The importance of measuring (13)N-ammonia metabolites in blood
Author(s)
Keiding, S; Sørensen, M; Munk, OL; Bender, D
Year
2010
Is Peer Reviewed?
1
Journal
Metabolic Brain Disease
ISSN:
0885-7490
EISSN:
1573-7365
Volume
25
Issue
1
Page Numbers
49-56
Language
English
PMID
20217201
DOI
10.1007/s11011-010-9181-2
Abstract
Dynamic 13N-ammonia PET is used to assess ammonia metabolism in brain, liver and muscle based on kinetic modeling of metabolic pathways, using arterial blood 13N-ammonia as input function. Rosenspire et al. (1990) introduced a solid phase extraction procedure for fractionation of 13N-content in blood into 13N-ammonia, 13N-urea, 13N-glutamine and 13N-glutamate. Due to a radioactive half-life for 13N of 10 min, the procedure is not suitable for blood samples taken beyond 5–7 min after tracer injection. By modifying Rosenspire’s method, we established a method enabling analysis of up to 10 blood samples in the course of 30 min. The modified procedure was validated by HPLC and by 30-min reproducibility studies in humans examined by duplicate 13N-ammonia injections with a 60-min interval. Blood data from a 13N-ammonia brain PET study (from Keiding et al. 2006) showed: (1) time courses of 13N-ammonia fractions could be described adequately by double exponential functions; (2) metabolic conversion of 13N-ammonia to 13N-metabolites were in the order: healthy subjects > cirrhotic patients without HE > cirrhotic patients with HE; (3) kinetics of initial tracer distribution in tissue can be assessed by using total 13N-concentration in blood as input function, whereas assessment of metabolic processes requires 13N-ammonia measurements.
Tags
IRIS
•
Ammonia
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Physical-Chemical/Mechanistic/Toxicokinetics Studies
Toxicokinetics
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