The experimental program will be directed toward an elucidation of the factors which regulate ammonia synthesis by the mammalian kidney. Studies utilizing isolated renal cortical mitochondria will be performed to define the interrelationships between bicarbonate ion and H+ in regulating glutamine and glutamate metabolism. These studies will be extended to the intact cell utilizing 15N-glutamine and 14C-glutamine to define further the regulatory steps and pathways. Kinetic studies are also planned defining the characteristics of glutamine transport across the inner mitochondrial membrane. As part of these studies, we will evaluate the role of transport and metabolism of glutamate and Alpha-ketoglutarate on glutamine transport and deamidation. To provide further insight into the factors controlling the accelerated rate of glutamate dehydrogenase flux in acidosis, the role of the mitochondrial oxidation reduction potential and protein synthesis will be assessed. The control of Alpha-ketoglutarate dehydrogenase flux will be investigated in detail by assessment of the role of calcium and H+ on the enzyme in kidney and liver. As part of this evaluation, mitochondrial free calcium and mitochondrial calcium efflux will be measured as a function of external pH. Utilizing cell fractionation methods, analysis of metabolite and pH profiles in the cytosolic and mitochondrial compartments of isolated renal tubules will be performed to understand better alterations in renal metabolism in acidosis. Of particular interest will be a determination of the contemporaneous changes in the cytosolic and mitochondrial pH as a function of external pH changes to determine whether metabolic rates may be effected by the pH gradient across the plasma and, particularly, the inner mitochondrial membrane. These studies will provide further insight into the biochemical mechanisms underlying the control of renal ammoniagenesis.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK036822-03
Application #
3235335
Study Section
General Medicine B Study Section (GMB)
Project Start
1985-07-01
Project End
1989-06-30
Budget Start
1987-07-01
Budget End
1988-06-30
Support Year
3
Fiscal Year
1987
Total Cost
Indirect Cost
Name
Virginia Commonwealth University
Department
Type
Schools of Medicine
DUNS #
City
Richmond
State
VA
Country
United States
Zip Code
23298
Drewnowska, K; Schoolwerth, A C (1997) Mechanism(s) regulating matrix pH in rat kidney mitochondria. Contrib Nephrol 121:62-8
Drewnowska, K; Labruyere, W T; van den Hoff, M J et al. (1997) Stimulation of phosphoenolpyruvate carboxykinase gene expression in cultured LLC-PK1-F+ cells. Contrib Nephrol 121:25-30
Drewnowska, K; Schoolwerth, A C (1994) Stimulatory effect of calcium on metabolism and its sensitivity to pH in kidney mitochondria. Am J Physiol 267:F153-9
Boon, L; Blommaart, P J; Meijer, A J et al. (1994) Effect of chronic acidosis on hepatic amino acid uptake and gene regulation: implications for control of acid-base balance. Contrib Nephrol 110:138-43
Boon, L; Blommaart, P J; Meijer, A J et al. (1994) Acute acidosis inhibits liver amino acid transport: no primary role for the urea cycle in acid-base balance. Am J Physiol 267:F1015-20
Schoolwerth, A C; deBoer, P; Moorman, A F et al. (1994) Time course of changes in mRNAs for enzymes of glutamine metabolism in kidney during metabolic acidosis. Contrib Nephrol 110:127-32
Boon, L; Blommaart, P J; Meijer, A J et al. (1994) Acute acidosis inhibits hepatic amino acid uptake: implications for regulation of acid-base balance. Contrib Nephrol 110:133-7
Waybill, M M; Clore, J N; Emerick, R A et al. (1994) Effects of corticosteroids on urinary ammonium excretion in humans. J Am Soc Nephrol 4:1531-7
Schoolwerth, A C; deBoer, P A; Moorman, A F et al. (1994) Changes in mRNAs for enzymes of glutamine metabolism in kidney and liver during ammonium chloride acidosis. Am J Physiol 267:F400-6
Schoolwerth, A C; Smith, B C; Drewnowska, K (1992) Regulation of glutamine metabolism in dog kidney cortex: effect of pH and chronic acidosis. Am J Physiol 262:F1007-14

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