Ovine Hepatic Metabolism. II. The Effect of Osmolarity and Ph of the Perfusion Medium on Hepatic Uptake of Ammonia and Nitrogen Excretion

摘要

The present investigation was carried out to assess the influence of changing perfusion medium osmolarity and pH with or without additional amino acid on the hepatic uptake of ammonia and production of urea and glutamine. To elucidate this effect, the caudal liver lobes of twenty Merino sheep (24-35 kg) were perfused using a non-reticulating perfusion model for 3-4 h using Krebs-Henseliet buffer solution containing 2.1 mM lactate, 0.3 mM pyruvate, 10 IU heparin m 1 at 37 C and gassed with O2-CO2 (95:5 v/v). An increase of perfusion osmolarity from 300 mosmol L 1 to 330 mosmol L 1 resulted in an increase in hepatic uptake of ammonia from 1200-nmol g 1 min 1 to 1900 nmol g min 1, thus assisting the hepatic clearance of ammonia. Similarly, hepatic glutamine production rosed from 48 to 177 nmol g 1 min 1. As the influent pH rose, a decline in urea and glutamine production was observed. The additions of amino acids favour glutamine hepatic uptake rather than production.