This proposal entails a comprehensive examination of the mechanisms controlling hepatic ureagenesis and ammonia detoxification in isolated hepatocytes and the isolated perfused liver. The work will address four primary themes: (1) identification of those amino acids serving as precursor to ammonia and urea N in a variety of metabolic conditions; (2) the role of the purine nucleotide cycle in furnishing the nitrogen utilized for the synthesis of either urea of glutamine; (3) the role of various effectors and/or inhibitors of ureagenesis in determining the sources of urea nitrogen; and (4) the effect(s) of hydrogen ion concentration in regulating nitrogen flux through the liver. The latter theme will receive special attention through the study of hepatic N metabolism in rats made acutely or chronically acidotic or alkalotic. A unique feature of the work is the use of physiologic medium containing most of the amino acids normally present in the extracellular fluid, only one of which will be labelled with 15N or 13C. By utilizing both gas chromatography-mass spectrometry and nuclear magnetic resonance to quantify stable isotopic enrichment in ammonia, urea, amino acids and adenine nucleotides, it will be possible to measure metabolite flux and to identify important precursor-product relationships in a manner which has been hitherto impossible. The data do obtained will be of scientific import by deepening our understanding of ureagenesis and of hepatic nitrogen metabolism. The rational clinical management of patients with liver disease presupposes such a scientific foundation.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
1R01DK039348-01
Application #
3239169
Study Section
Biochemistry Study Section (BIO)
Project Start
1988-04-01
Project End
1993-03-31
Budget Start
1988-04-01
Budget End
1989-03-31
Support Year
1
Fiscal Year
1988
Total Cost
Indirect Cost
Name
Children's Hospital of Philadelphia
Department
Type
DUNS #
073757627
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Brosnan, J T; Brosnan, M E; Charron, R et al. (1997) Incorporation of 15N-labelled precursors into urea isotopomers. Contrib Nephrol 121:156-62
Nissim, I; Weinberg, J M (1996) Glycine attenuates Fanconi syndrome induced by maleate or ifosfamide in rats. Kidney Int 49:684-95
Nissim, I; Yudkoff, M; Brosnan, J T (1996) Regulation of [15N]urea synthesis from [5-15N]glutamine. Role of pH, hormones, and pyruvate. J Biol Chem 271:31234-42
Brosnan, J T; Brosnan, M E; Charron, R et al. (1996) A mass isotopomer study of urea and glutamine synthesis from 15N-labeled ammonia in the perfused rat liver. J Biol Chem 271:16199-207
Tannen, R L; Nissim, I; Sahi, A (1996) Hormonal mediators of ammoniagenesis: mechanism of action of PGF2 alpha and the implications for other hormones. Kidney Int 50:15-25
Nissim, I; States, B; Nissim, I et al. (1995) Hormonal regulation of glutamine metabolism by OK cells. Kidney Int 47:96-105
Foreman, J W; Benson, L L; Wellons, M et al. (1995) Metabolic studies of rat renal tubule cells loaded with cystine: the cystine dimethylester model of cystinosis. J Am Soc Nephrol 6:269-72
Sahai, A; Nissim, I; Sandler, R S et al. (1995) Prostaglandin F2 alpha- and 12-O-tetradecanoylphorbol-13-acetate-induced alterations in the pathways of renal ammoniagenesis. J Am Soc Nephrol 5:1792-8
Nissim, I; States, B; Nissim, I et al. (1994) pH and hormonal regulation of ammoniagenesis in cultured OK cells. Contrib Nephrol 110:30-40
Nissim, I; Sahai, A; Sandler, R S et al. (1994) The intensity of acidosis differentially alters the pathways of ammoniagenesis in LLC-PK1 cells. Kidney Int 45:1014-9

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