title: Sources of ammonia for urea synthesis in isolated rat liver cells.
abstract: L-Leucine inhibits urea synthesis in rat hepatocytes from a number of nitrogen sources, including ammonia. The inhibition by L-leucine is largely overcome by addition of 1 mM L-ornithine, suggesting that the main site of L-leucine action is at ornithine transcarbamylase, rather than at glutamate dyhydrogenase. L-Norvaline is a more potent inhibitor of urea synthesis than is L-leucine, but again the inhibition is largely counteracted by L-ornithine. Addition of aminooxyacetate and L-norvaline strongly suppresses the formation of glucose and lactate from L-asparagine, suggesting that an alternate pathway of aspartate metabolism, the purine nucleotide cycle, in not a major pathway. Hadacidin, an inhibitor of adenylosuccinate synthetase, an enzyme of the purine nucleotide cycle, has no effect on urea synthesis in rat liver cells.
mesh_terms: D000409:Alanine / Q000378:metabolism; D000625:Aminooxyacetic Acid / Q000494:pharmacology; D000643:Ammonium Chloride / Q000378:metabolism*; D000818:Animals; D001216:Asparagine / Q000378:metabolism; D005947:Glucose / Q000096:biosynthesis; D005973:Glutamine / Q000378:metabolism; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D007773:Lactates / Q000096:biosynthesis; D007930:Leucine / Q000494:pharmacology; D008099:Liver / Q000378:metabolism*; D009952:Ornithine / Q000494:pharmacology; D051381:Rats; D014508:Urea / Q000096:biosynthesis*; D014633:Valine / Q000494:pharmacology
chemical_list: D007773:Lactates; D000643:Ammonium Chloride; D005973:Glutamine; D000625:Aminooxyacetic Acid; D001216:Asparagine; D014508:Urea; D009952:Ornithine; D007930:Leucine; D014633:Valine; D005947:Glucose; D000409:Alanine; D005998:Glycine