European Journal of Nuclear Medicine

, Volume 28, Issue 12, pp 1770–1775

Positron emission tomography of hepatic first-pass metabolism of ammonia in pig

  • Susanne Keiding
  • Ole Munk
  • Klaus Roelsgaard
  • Dirk Bender
  • Ludvik Bass
Original Article

DOI: 10.1007/s00259-001-0659-3

Cite this article as:
Keiding, S., Munk, O., Roelsgaard, K. et al. Eur J Nucl Med (2001) 28: 1770. doi:10.1007/s00259-001-0659-3

Abstract

Hepatic first-pass metabolism plays a key role in metabolic regulation and drug metabolism. Metabolic processes can be quantified in vivo by positron emission tomography scanning (PET). We wished to develop a PET technique to measure hepatic first-pass metabolism of ammonia. Seven anaesthetised pigs were given positron-labelled ammonia, 13NH3, into the portal vein and into the vena cava as successive 2-min infusions followed by 22-min dynamic liver scanning. Vena cava infusion data were used to account for recirculation of tracer and metabolites following the portal vein infusion. The scan data were analysed by a model of sinusoidal zonation of ammonia metabolism with periportal urea formation and perivenous formation of glutamine. The hepatic extraction fraction of 13NH3 was 0.73±0.16 (mean±SD, n=7 pigs). Values of clearance of ammonia to urea and to glutamine were obtained, as were rate constants for washout of these two metabolites. Overall, the modelling showed half of the ammonia uptake to be converted to urea and half to glutamine. The washout rate constant for glutamine was about one-tenth of that for urea. We conclude that hepatic first-pass metabolism of ammonia was successfully assessed by PET.

Positron emission tomography Liver drug metabolism

Copyright information

© Springer-Verlag 2001

Authors and Affiliations

  • Susanne Keiding
    • 1
  • Ole Munk
    • 1
  • Klaus Roelsgaard
    • 1
  • Dirk Bender
    • 1
  • Ludvik Bass
    • 3
  1. 1.PET Centre, Aarhus University Hospital, DK 8000 AarhusDenmark
  2. 2.Department of Medicine V, Aarhus University Hospital, AarhusDenmark
  3. 3.Department of Mathematics, University of Queensland, BrisbaneAustralia