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Human (13)N-ammonia PET Studies: The Importance of Measuring (13)N-ammonia Metabolites in Blood

Human (13)N-ammonia PET Studies: The Importance of Measuring (13)N-ammonia Metabolites in Blood

Susanne Keiding, Michael Sørensen, Ole Lajord Munk, Dirk Bender

Metab Brain Dis. 2010 Mar;25(1):49-56.

PMID: 20217201

Abstract:

Dynamic (13)N-ammonia PET is used to assess ammonia metabolism in brain, liver and muscle based on kinetic modeling of metabolic pathways, using arterial blood (13)N-ammonia as input function. Rosenspire et al. (1990) introduced a solid phase extraction procedure for fractionation of (13)N-content in blood into (13)N-ammonia, (13)N-urea, (13)N-glutamine and (13)N-glutamate. Due to a radioactive half-life for (13)N 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 (13)N-ammonia injections with a 60-min interval. Blood data from a (13)N-ammonia brain PET study (from Keiding et al. 2006) showed: (1) time courses of (13)N-ammonia fractions could be described adequately by double exponential functions; (2) metabolic conversion of (13)N-ammonia to (13)N-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 (13)N-concentration in blood as input function, whereas assessment of metabolic processes requires (13)N-ammonia measurements.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP454675764	13,6-N-Sulfinylacetamidopentacene		454675-76-4	Price

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