title: Nitrogen metabolism in the isolated perfused rat liver. Nitrogen balance, redox state and rates of proteolysis.
abstract: Nitrogen balances were measured in isolated perfused rat livers in the presence and absence of nitrogen donors. In all instances the balance apparently was incomplete. The expression [alanine][alpha-oxoglutarate]/[pyruvate][glutamate] remained fairly constant under the metabolic conditions studied, indicating that it may be at near-equilibrium. The source of the extra nitrogen seems to be derived from increased hepatic proteolysis. The addition of a nitrogen donor to the perfusate arrested proteolysis, as did the addition of pyruvate. The free mitochondrial [NAD(+)]/[NADH] ratio, calculated from the glutamate dehydrogenase and beta-hydroxybutyrate dehydrogenase reactants, showed similar values and exhibited parallel changes under most metabolic situations studied. These results suggest that, under the reported experimental conditions, both dehydrogenases share a common mitochondrial NAD pool. Glutamate dehydrogenase plays an important role in hepatic nitrogen metabolism in vivo.
mesh_terms: D000409:Alanine / Q000378:metabolism; D049148:Aminoacylation; D000641:Ammonia / Q000378:metabolism; D000818:Animals; D001322:Autoanalysis; D002498:Centrifugation; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D005971:Glutamates / Q000378:metabolism; D006884:Hydroxybutyrate Dehydrogenase / Q000378:metabolism; D066298:In Vitro Techniques; D007656:Ketoglutaric Acids / Q000378:metabolism; D007700:Kinetics; D007773:Lactates / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008297:Male; D008930:Mitochondria, Liver / Q000032:analysis; D009243:NAD / Q000032:analysis; D009584:Nitrogen / Q000378:metabolism*; D010084:Oxidation-Reduction; D010447:Peptide Hydrolases / Q000378:metabolism; D010477:Perfusion; D011773:Pyruvates / Q000378:metabolism; D051381:Rats; D014508:Urea / Q000378:metabolism; D014633:Valine / Q000378:metabolism
chemical_list: D005971:Glutamates; D007656:Ketoglutaric Acids; D007773:Lactates; D011773:Pyruvates; D009243:NAD; D000641:Ammonia; D014508:Urea; D006884:Hydroxybutyrate Dehydrogenase; D005969:Glutamate Dehydrogenase; D010447:Peptide Hydrolases; D014633:Valine; D009584:Nitrogen; D000409:Alanine