The goal of this project is to determine the stoichiometric relationships between O2 consumption, ATP synthesis, and Na transport by the intact kidney in vivo. The Na/O2 ratio of the kidney is greater than the theoretical maximum of 18 (assuming ATP/O = 3, ATP/O2 = 6, Na/ATP = 3). It has been proposed that the high Na/O2 is due to passive reabsorption of Na in the proximal tubule. This hypothesis will be tested by measuring ATP synthesis using 31P NMR saturation transfer and simultaneously determining O2 consumption and Na reabsorption by clearance techniques. In order to test certain assumptions which are necessary for an unambiguous interpretation of the NMR results, we will: 1) Reduce or eliminate the contribution of extracellular Pi and red cell metabolites to the intracellular Pi peak. 2) Determine if a NMR-invisible Pi pool participates in ATP synthesis by comparing the rates of synthesis and hydrolysis. 3) Determine if NMR measures ATP synthesis or Pi-ATP exchange by measuring the sensitivity of the reaction to cyanide or rotenone; ATP synthesis is inhibited by these agents while ATP-Pi exchange is not. 4) Determine if the ATP/O can be measured with reasonable precision by error analysis experiments. It is expected that these experiments will demonstrate with reasonable certainty that the ATP/O in vivo is 2-3. It has been proposed that the high Na/O2 of the kidney is due to passive Na reabsorption (Na/ATP greater than 3) in the proximal tubule. To test this we will measure: 1) the effect of inhibiting the loop of Henle with furosemide and 2) the effect of inhibiting the proximal tubule with acetazolamide, mannitol, or vanadate. The results should indicate the tubular segment responsible for the high Na/O2. Finally, to determine if the stoichiometry between O2 consumption, ATP synthesis, and Na transport varies in a regulated fashion, we will measure ATP/O and Na/ATP during the following maneuvers: 1) changes of glomerular filtration rate. 2) Hypoxia. 3) Hypo - and hyperthyroidism. The significance of this project is that: 1) Important assumptions necessary to interpret saturation transfer measurements of ATP synthesis will be tested. 2) The stoichiometry of oxidative phosphorylation in vivo will be measured. 3) The site of the high Na/ATP in the kidney will be determined. 4) Factors which may alter coupling of oxidative phosphorylation and ATP utilization for Na transport may be identified.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK033293-03
Application #
3231677
Study Section
Physical Biochemistry Study Section (PB)
Project Start
1984-09-30
Project End
1987-08-31
Budget Start
1986-09-01
Budget End
1987-08-31
Support Year
3
Fiscal Year
1986
Total Cost
Indirect Cost
Name
University of California San Francisco
Department
Type
Schools of Medicine
DUNS #
073133571
City
San Francisco
State
CA
Country
United States
Zip Code
94143
Higuchi, T; Graham, S H; Fernandez, E J et al. (1997) Effects of severe global ischemia on N-acetylaspartate and other metabolites in the rat brain. Magn Reson Med 37:851-7
Ebisu, T; Rooney, W D; Graham, S H et al. (1996) MR spectroscopic imaging and diffusion-weighted MRI for early detection of kainate-induced status epilepticus in the rat. Magn Reson Med 36:821-8
Hugg, J W; Maudsley, A A; Weiner, M W et al. (1996) Comparison of k-space sampling schemes for multidimensional MR spectroscopic imaging. Magn Reson Med 36:469-73
Miller, R G; Carson, P J; Moussavi, R S et al. (1995) Factors which influence alterations of phosphates and pH in exercising human skeletal muscle: measurement error, reproducibility, and effects of fasting, carbohydrate loading, and metabolic acidosis. Muscle Nerve 18:60-7
Meyerhoff, D J; MacKay, S; Sappey-Marinier, D et al. (1995) Effects of chronic alcohol abuse and HIV infection on brain phosphorus metabolites. Alcohol Clin Exp Res 19:685-92
Ebisu, T; Rooney, W D; Graham, S H et al. (1994) N-acetylaspartate as an in vivo marker of neuronal viability in kainate-induced status epilepticus: 1H magnetic resonance spectroscopic imaging. J Cereb Blood Flow Metab 14:373-82
Husted, C A; Matson, G B; Adams, D A et al. (1994) In vivo detection of myelin phospholipids in multiple sclerosis with phosphorus magnetic resonance spectroscopic imaging. Ann Neurol 36:239-41
Husted, C A; Duijn, J H; Matson, G B et al. (1994) Molar quantitation of in vivo proton metabolites in human brain with 3D magnetic resonance spectroscopic imaging. Magn Reson Imaging 12:661-7
Maudsley, A A; Matson, G B; Hugg, J W et al. (1994) Reduced phase encoding in spectroscopic imaging. Magn Reson Med 31:645-51
Husted, C A; Goodin, D S; Hugg, J W et al. (1994) Biochemical alterations in multiple sclerosis lesions and normal-appearing white matter detected by in vivo 31P and 1H spectroscopic imaging. Ann Neurol 36:157-65

Showing the most recent 10 out of 38 publications