Sources of ammonia for urea synthesis in isolated rat liver cells

• Published in: Biochimica et biophysica acta Vol. 496; no. 2; pp. 249 - 254
• Main Author: Rognstad, Robert
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 28.02.1977
• Subjects: Alanine - metabolism; Aminooxyacetic Acid - pharmacology; Ammonium Chloride - metabolism; Animals; Asparagine - metabolism; Glucose - biosynthesis; Glutamine - metabolism; Glycine - analogs & derivatives; Glycine - pharmacology; Lactates - biosynthesis; Leucine - pharmacology; Liver - metabolism; Ornithine - pharmacology; Rats; Urea - biosynthesis; Valine - pharmacology
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/0304-4165(77)90306-3

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 synthesiss 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.