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Hepatic microcirculation assessed by positron emission tomography of first‐pass ammonia metabolism in porcine liver
Author(s) -
Keiding Susanne,
Munk Ole Lajord,
Vilstrup Hendrik,
Nielsen Dennis Tønner,
Roelsgaard Klaus,
Bass Ludvik
Publication year - 2005
Publication title -
liver international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.873
H-Index - 110
eISSN - 1478-3231
pISSN - 1478-3223
DOI - 10.1111/j.1478-3231.2005.01032.x
Subject(s) - metabolism , urea , chemistry , glutamine , positron emission tomography , coefficient of variation , nuclear medicine , medicine , endocrinology , biochemistry , amino acid , chromatography
Aims/Background: Intrahepatic branching of the hepatic artery (HA) to liver microcirculatory units, the acini, is more heterogeneous than that of the portal vein (PV). Furthermore, part of HA blood enters the sinusoid partially downstream between the in‐ and outlets. We examined the effects of these vascular variations on porcine hepatic first‐pass ammonia metabolism, which is characterised by high uptake and separate periportal urea and perivenous glutamine formations. Methods:13 NH 3 was given via the PV, HA or caval vein, followed by 22 min dynamic liver positron emission tomography (PET) recordings in six pigs. Heterogeneity of liver 13 N‐metabolism was quantified by the coefficient of variation of tissue 13 N‐radioactivity measured 10 min after tracer infusion. Sinusoidal zonal clearances of 13 NH 3 into 13 N‐urea and 13 N‐glutamine were calculated by kinetic PET modelling. Results: Liver metabolic heterogeneity was 0.65±0.20 (mean±SD, n =6) following 13 NH 3 ‐infusion into HA, 0.34±0.17 into PV and 0.10±0.02 into the caval vein. Clearance of 13 NH 3 to 13 N‐urea was of similar magnitude following 13 NH 3 administration into HA and PV: 0.27±0.11 ml/min/g (mean±SD) and 0.29±0.09 ml/min/g, respectively. Clearances of 13 NH 3 to 13 N‐glutamine when 13 NH 3 was given into HA and PV were also similar: 0.47±0.18 and 0.50±0.13 ml/min/g, respectively. Conclusions: The present measurements of the hepatic metabolism of 13 NH 3 showed metabolic heterogeneity compatible with variation of the HA supply of the acini. Second, results of PET modelling of the sinusoidal zonation metabolism of 13 NH 3 to 13 N‐urea and to 13 N‐glutamine did not indicate metabolically important partial downstream arterial entry into the sinusoids.