This proposal entails a comprehensive examination of the mechanism(s) controlling renal amino acid metabolism, ammoniagenesis and gluconeogenesis in various acid base states. The work will address five primary themes: (1) the metabolic signals initiating augmented ammoniagenesis in acidosis; (2) the rate limiting metabolic pathway(s) for ammonia production; (3) the role of effectors and/or inhibitors of ammoniagenesis on the underlying biochemistry; (4) the putative relationship between renal ammonia and glucose formation; (5) the biochemical adaptation occurring both during the induction of and recovery from acidosis and alkalosis. The core hypothesis of the work is that diminished flux through the citrate synthetase pathway is an initial step in a coordinated sequence of events leading to an increased rate of ammoniagenesis in acidosis. A corollary hypothesis is that the diminution of the alpha-ketoglutarate pool secondary to reduced flux through citrate synthetase is accompanied by enhanced flux through glutamate dehydrogenase toward oxidative deamination of glutamate with the release of NH3. We also will explore the possibility that the augmentation of ammoniagenesis and gluconeogenesis in acidosis are (or are not) inter-dependent phenomenon subject to common metabolic signals and controls, with the increase of glucose production providing an outlet for glutamate carbon. The significance of diminished flux through the glutamine synthetase reaction in abetting HN3 production will be studied as well. These topics will examined by incubating isolated rat renal tubules with 15N and/or 13C labelled precursors in the presence and absence of metabolic modulators and/or inhibitors. Subsequent determination of important precursor-product relationships and flux rates will be made using gas chromatography-mass spectrometry and/or nuclear magnetic resonance spectroscopy. The data so obtained will be of scientific import by deepening our understanding of renal ammoniagenesis in response to perturbations of hydrogen ion homeostasis. The project will evaluate such adaptations in terms of the stage of acidosis or alkalosis, i.e., during the induction of or recovery from either state.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK034771-06
Application #
3233010
Study Section
General Medicine B Study Section (GMB)
Project Start
1984-12-01
Project End
1991-07-31
Budget Start
1989-12-01
Budget End
1991-07-31
Support Year
6
Fiscal Year
1990
Total Cost
Indirect Cost
Name
Children's Hospital of Philadelphia
Department
Type
DUNS #
073757627
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Sahai, A; Nissim, I; Tannen, R L (1991) Pathways of acute pH regulation of ammoniagenesis in LLC-PK1 cells: study with [15N]glutamine. Am J Physiol 261:F481-7
Nissim, I; States, B; Nissim, I et al. (1991) The role of gamma-glutamyl transpeptidase in glutamine metabolism by cultured human kidney cells. Contrib Nephrol 92:191-9
Nissim, I; Nissim, I; Yudkoff, M (1991) Adaptation of renal tricarboxylic acid cycle metabolism to various acid-base states: study with [3-13C,5-15N]glutamine. Miner Electrolyte Metab 17:21-31
Nissim, I; Wehrli, S; States, B et al. (1991) Analysis and physiological implications of renal 2-oxoglutaramate metabolism. Biochem J 277 ( Pt 1):33-8
Weinberg, J M; Nissim, I; Roeser, N F et al. (1991) Relationships between intracellular amino acid levels and protection against injury to isolated proximal tubules. Am J Physiol 260:F410-9
Nissim, I; Nissim, I; Yudkoff, M (1990) Carbon flux through tricarboxylic acid cycle in rat renal tubules. Biochim Biophys Acta 1033:194-200
Nissim, I; Korzets, Z (1990) Ammonia metabolism in cultured renal cells. Miner Electrolyte Metab 16:270-6
Nissim, I; Yudkoff, M; Nissim, I et al. (1989) Effect of 5-amino-4-imidazolecarboxamide riboside (AICA-riboside) on the purine nucleotide synthesis and growth of rat kidney cells in culture: study with [15N]aspartate. J Cell Physiol 138:536-40
Nissim, I; States, B (1989) Ammoniagenesis by cultured human renal cortical epithelial cells: study with 15N. Am J Physiol 256:F187-96
Nissim, I; Yudkoff, M; Segal, S (1988) Interrelationships between renal TCA-cycle metabolism and ammoniagenesis: studies with 13C-NMR and GC-MS. Contrib Nephrol 63:60-70