Abstract
PET is a functional imaging technique suitable for studies of brain ammonia metabolism. Dynamic 13N-ammonia PET yields time-courses of radioactivity concentrations in brain (PET camera) and blood (samples). Ahl et al. (Hepatology 40:73–79, 2004) and Keiding et al. (Hepatology 43:42–50, 2006) analysed such data in patients with HE by a kinetic model accounting for transfer of 13N-ammonia across the blood–brain barrier (BBB) and intracellular formation of 13N-glutamine. Initial unidirectional 13N-ammonia transfer across BBB was characterized by the permeability-surface area product PSBBB (ml blood min−1 ml−1 tissue). There was a tendency to lower PSBBB values in patients with cirrhosis and HE than in patients with cirrhosis without HE and healthy controls but the differences were not statistically significant. Keiding et al. (Hepatology 43:42–50, 2006) also calculated PSmet (ml blood min−1 ml−1 tissue) as a measure of the combined transfer of 13N-ammonia across BBB and subsequent intracellular metabolism of 13N-ammonia; neither did this PS-value show significant difference between the groups of subjects. Net flux of ammonia from blood into intracellular metabolites was linearly correlated to arterial ammonia. In conclusion, basic brain ammonia kinetics was not changed significantly in patients with cirrhosis +/- HE compared to healthy controls. Blood ammonia seems to be the more important factor for increased brain ammonia uptake in HE.
Similar content being viewed by others
References
Ahl B, Weissenborn K, van den Hoff J, Fischer-Wasels D, Köstler H, Hecker H, Burchert W (2004) Regional differences in cerebral blood flow and cerebral ammonia metabolism in patients with cirrhosis. Hepatology 40:73–79
Crone C (1964) Permeability of capillaries in various organs as determined by use of the indicator diffusion method. Acta Physiol Scand 58:292–305
Goldbecker A (2007, this conference) Cerebral ammonia metabolism in liver fibrosis. In: Metabolic brain disease (eds. xxx); in press
Keiding S, Sørensen M (2007) Hepatic removal kinetics: importance for quantitative measurements of liver function. In: Rhodés J, Benhamou JP, Blei A, Reichen J, Rizzetto M, (eds.) Textbook of hepatology: from basic science to clinical practice, 3rd edn. Blackwell, pp 468–478
Keiding S, Munk OL, Schiøtt KM, Hansen SB (2000) Dynamic 2-[18F]fluoro-2-deoxy-D-glucose positron emission tomography of liver tumors without blood sampling. Eur J Nucl Med 27:407–412
Keiding S, Sørensen M, Bender D, Munk OL, Ott P, Vilstrup H (2006) Brain metabolism of 13N-ammonia during acute hepatic encephalopathy in cirrhosis measured by PET. Hepatology 43:42–50
Kety SS (1951). The theory and application of the exchange of inert gas at lung and tissues. Pharmacol Rev 3:1–41
Lockwood AH, McDonald JM, Reiman RE, Gelbard AS, Laughlin JS, Duffy TE, Plum F (1979) The dynamics of ammonia metabolism in man. Effects of liver disease and hyperammonemia. J Clin Invest 63:449–460
Lockwood AH, Bolomey L, Napoleon F (1984) Blood–brain barrier to ammonia in humans. J Cereb Blood Flow Metab 4:516–522
Lockwood AH, Yap EW, Wong WH (1991) Cerebral ammonia metabolism in patients with severe liver disease and minimal hepatic encephalopathy. J Cereb Blood Flow Metab 11:337–341
Ott P, Larsen FS (2004) Blood–brain barrier permeability to ammonia in liver failure: a critical reappraisal. Neurochem Int 40:185–198
Phelps ME, Hoffman EJ, Coleman RE, Welch MJ, Raichle ME, Weiss ES (1976) Tomographic images of blood pool and perfusion in brain and heart. J Nucl Med 17:603–612
Phelps ME, Huang SC, Hoffman EJ, Selin C, Kuhl DE (1981) Cerebral extraction of 13N-ammonia: its dependence on cerebral blood flow and capillary permeability-surface area product. Stroke 12:607–619
Renkin EM (1959) Transport of potassium-42 from blood to tissue in isolated mammalian skeletal muscles. Am J Physiol 197:1205–1210
Rosenspire KC, Schwaiger M, Mangner TJ, Hutchins GD, Sutorik A, Kuhl DE (1990) Metabolic fate of [13N]ammonia in human and canine blood. J Nucl Med 31:163–167
Sørensen M, Keiding S (2006a) Ammonia metabolism in cirrhosis. In: Häussinger D, Kircheis G, Schliess F (Eds) Hepatic encephalopathy and nitrogen metabolism. Springer, pp 406–419
Sørensen M, Keiding S (2006b) Reply to letter to the Editor by Lockwood A, Wack D. The brain permeability-surface product for ammonia. Hepatology 44:1053–1054
Sørensen M, Keiding S (2007) Positron emission tomography of the liver. In: Rhodés J, Benhamou JP, Blei A, Reichen J, Rizzetto M (eds) Textbook of hepatology: from basic science to clinical practice, 3rd edn. Blackwell, pp 561–566
Weissenborn K, Bokemeyer M, Ahl B, Fischer-Wasels D, Giewekemeyer K, van den Hoff J, Köstler G, Berding G (2004) Functional imaging of the brain in patients with liver cirrhosis. Metab Brain Dis 19:269–280
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Sørensen, M., Keiding, S. New findings on cerebral ammonia uptake in HE using functional 13N-ammonia PET. Metab Brain Dis 22, 277–284 (2007). https://doi.org/10.1007/s11011-007-9066-1
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11011-007-9066-1