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Title: NMR studies of renal phosphate metabolites in vivo: Effects of hydration and dehydration

Abstract

The present study characterizes the {sup 31}P-nuclear magnetic resonance (NMR) spectrum of rabbit kidneys in vivo and evaluates the effect of hydration on phosphorous metabolites including the organic solute glycerophosphorylcholine (GPC). Cortical phosphorylethanolamine is the predominant component of the phosphomonoester region of the {sup 31}P spectrum. The contribution of blood to the spectrum is mainly from 2,3 diphosphoglycerate, which comprises {approximately}30% of the inorganic phosphate region. Acute infusion of 0.9% saline decreases the sodium content of the inner medulla by >50% in 15 min as shown by {sup 23}Na imaging. Despite this medullary Na dilution, no change in renal GPC content was observed for >1 h even with the addition of furosemide or furosemide and antidiuretic hormone. However, 20 h of chronic dehydration with 0.45% saline did result in a 30% decrease in renal GPC content when compared with dehydrated animals. These findings are consistent with GPC not playing a role in the short-term regulation of the medullary intracellular milieu in response to acute reductions in medullary Na content.

Authors:
; ;  [1]
  1. (National Institutes of Health, Bethesda, MD (USA))
Publication Date:
OSTI Identifier:
6038124
Resource Type:
Journal Article
Resource Relation:
Journal Name: American Journal of Physiology; (USA); Journal Volume: 255:4
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; PHOSPHOLIPIDS; NUCLEAR MAGNETIC RESONANCE; CHOLINE; DEHYDRATION; HYDRATION; IN VIVO; INOSITOLS; KIDNEYS; METABOLITES; PHOSPHORUS 31; RABBITS; ALCOHOLS; AMINES; AMMONIUM COMPOUNDS; ANIMALS; BODY; CARBOHYDRATES; DRUGS; ESTERS; HYDROXY COMPOUNDS; ISOTOPES; LIGHT NUCLEI; LIPIDS; LIPOTROPIC FACTORS; MAGNETIC RESONANCE; MAMMALS; MONOSACCHARIDES; NUCLEI; ODD-EVEN NUCLEI; ORGANIC COMPOUNDS; ORGANIC PHOSPHORUS COMPOUNDS; ORGANS; PHOSPHORUS ISOTOPES; QUATERNARY COMPOUNDS; RESONANCE; SACCHARIDES; SOLVATION; STABLE ISOTOPES; VERTEBRATES; 550601* - Medicine- Unsealed Radionuclides in Diagnostics

Citation Formats

Wolff, S.D., Eng, C., and Balaban, R.S. NMR studies of renal phosphate metabolites in vivo: Effects of hydration and dehydration. United States: N. p., 1988. Web.
Wolff, S.D., Eng, C., & Balaban, R.S. NMR studies of renal phosphate metabolites in vivo: Effects of hydration and dehydration. United States.
Wolff, S.D., Eng, C., and Balaban, R.S. 1988. "NMR studies of renal phosphate metabolites in vivo: Effects of hydration and dehydration". United States. doi:.
@article{osti_6038124,
title = {NMR studies of renal phosphate metabolites in vivo: Effects of hydration and dehydration},
author = {Wolff, S.D. and Eng, C. and Balaban, R.S.},
abstractNote = {The present study characterizes the {sup 31}P-nuclear magnetic resonance (NMR) spectrum of rabbit kidneys in vivo and evaluates the effect of hydration on phosphorous metabolites including the organic solute glycerophosphorylcholine (GPC). Cortical phosphorylethanolamine is the predominant component of the phosphomonoester region of the {sup 31}P spectrum. The contribution of blood to the spectrum is mainly from 2,3 diphosphoglycerate, which comprises {approximately}30% of the inorganic phosphate region. Acute infusion of 0.9% saline decreases the sodium content of the inner medulla by >50% in 15 min as shown by {sup 23}Na imaging. Despite this medullary Na dilution, no change in renal GPC content was observed for >1 h even with the addition of furosemide or furosemide and antidiuretic hormone. However, 20 h of chronic dehydration with 0.45% saline did result in a 30% decrease in renal GPC content when compared with dehydrated animals. These findings are consistent with GPC not playing a role in the short-term regulation of the medullary intracellular milieu in response to acute reductions in medullary Na content.},
doi = {},
journal = {American Journal of Physiology; (USA)},
number = ,
volume = 255:4,
place = {United States},
year = 1988,
month =
}
  • Ten normal volunteers were studied in the hydrated and dehydrated states with the new renal radiopharmaceutical technetium-99m N,N'-bis(mercapto acetyl)-2,3-diaminopropanoate ((/sup 99m/Tc)CO/sub 2/ DADS). The data were used to determine the effect of hydration and dehydration and to determine the normal range in each state. Visual evaluation of the images indicated that the first appearance of tracer in the collecting system was approximately the same in either state, that the concentration of tracer in the collecting system was always higher in the dehydrated state and that the ureters always appeared more segmented in the dehydrated state. Quantitative analysis of the imagesmore » indicated that the kidney to background ratio 1-2 min after injection was somewhat greater in the dehydrated state than in the hydrated state, that the size of the bladder was always greater in the hydrated state, and there was no difference in the amount of tracer in the bladder at 30 min after injection. The results define the normal hydrated and dehydrated (/sup 99m/Tc)CO/sub 2/ DADS renal study and identify several differences between the two states which can be explained primarily by differences in urine flow rates.« less
  • Changes of phosphate metabolism in brains of neonate, weaning and adult rats were compared using both in vivo and in vitro nuclear magnetic resonance spectra. Ratios of phosphocreatine/nucleoside triphosphate (PCr/NTP) were the same in neonatal brain in both in vivo and in vitro studies, but not in weaning and adult brains. This discrepancy may have resulted from extended cerebral hypoxia due to slowed freezing of the brain by the increased skull thickness and brain mass in the weaning and adult rats. Variations of in vitro extraction condition for this age-related study may lead to systematic errors in the adult rats.more » Nevertheless, the phosphomonoester/nucleoside triphosphate (PME/NTP) ratios in extracts of brain from neonatal rats were higher than those obtained in vivo. In addition, the glycerophosphorylethanolamine plus glycerophosphorylcholine/nucleoside triphosphate (GPE+GPC/NTP) ratios, which were not measurable in vivo, showed age-dependent increase in extracts of rat brain. Some of the phosphomonoester and phosphodiester molecules in rat brain may be undetectable in in vivo NMR analysis because of their interaction with cellular components. The total in vitro GPE and GPC concentration in brain from neonatal rat was estimated to be 0.34 mmole/g wet tissue.« less
  • The approach to equilibrium between carbon dioxide and bicarbonate has been followed by zero-order kinetics both from direction of CO/sub 2/ hydration and HCO/sub 3//sup -/ dehydration. The rates are monitored at 25.0/sup 0/C using stopped-flow indicator technique in H/sub 2/O as well as D/sub 2/O. The hydration of CO/sub 2/ is subject to catalysis by H/sub 2/O (k/sub 0/ = 2.9 x 10/sup -2/ s/sup -1/) and OH/sup -/ (k/sub OH/sup -// = 6.0 x 10/sup 3/ M/sup -1/ s/sup -1/). The value of 0.63 for the ratio k/sub OH/sup -///k/sub OD/sup -// is consistent with a mechanism utilizingmore » a direct nucleophilic attack of OH/sup -/ on CO/sub 2/. In reverse direction HCO/sub 3//sup -/ dehydration is catalyzed predominantly by H/sub 3/O/sup +/ (k/sub H/sub 3/O/sup +// 4.1 x 10/sup 4/ M/sup -1/ s/sup -1/) and to a much lesser degree by H/sub 2/O (k/sub 0/ = 2 x 10/sup -4/ s/sup -1/). The value of 0.56 for ratio k/sub H/sub 3/O/sup +///kD/sub 3/O/sup +// indicates that HCO/sub 3//sup -/ may be protonated either in a preequilibrium step or in a rate-determining dehydration step. Both the hydration of CO/sub 2/ and the dehydration of bicarbonate are subject to general catalysis. For CO/sub 2/, dibasic phosphate, a zinc imidazole complex, and a copper imidazole complex all enhanced the rate of hydration with respective rate coefficients of 3 x 10/sup -1/, 6.0, and 2.5 M/sup -1/ s/sup -1/. For bicarbonate, monobasic phosphate catalyzed the rate of dehydration (k/sub H/sub 2/PO/sub 4//sup -// = 1 x 10/sup -1/ M/sup -1/ s/sup -1/). Additionally in going from an ionic strength of 0.1 to 1.0 there was a negligible salt effect for the water-catalyzed hydration of CO/sub 2/. However, the rate constant for the hydronium ion catalyzed dehydration of HCO/sub 3//sup -/ was reduced from 4.1 x 10/sup 4/ M/sup -1/ s/sup -1/ to 2.3 x 10/sup 4/ M/sup -1/ s/sup -1/ for the same change in ionic strength. Finally the rate of CO/sub 2/ uptake by the complex Co(NH/sub 3/)/sub 5/OH/sub 2//sup 3 +/ was followed spectrophotometrically both in H/sub 2/O and D/sub 2/O to determine the solvent isotope effect for a reaction known to involve a nucleophilic attack of a Co(III)-hydroxo complex on CO/sub 2/.« less
  • No abstract prepared.
  • /sup 13/C kinetic isotope effects on the hydration of CO/sub 2/ and the dehydration of HCO/sub 3//sup -/ in aqueous solution have been measured by rapid removal of the product and conversion to an isotopically stable form, followed by isotope-ratio analysis. The isotope effect on hydration is k/sup 12//k/sup 13/ = 1.0069 +/- 0.0003 at 24/sup 0/C. The isotope effect on dehydration is 1.0147 +/- 0.0007. The ratio of these two values gives an equilibrium isotope effect of K/sup 12//K/sup 13/ = 1.0077, in good agreement with previously measured values. The small magnitudes of the kinetic isotope effects indicate thatmore » the transition state for conversion of HCO/sub 3//sup -/ to CO/sub 2/ is very similar to that of HCO/sub 3//sup -/. This information together with previously measured solvent isotope effects indicates that the mechanism of HCO/sub 3//sup -/ dehydration probably involves general-acid-catalyzed donation of a proton from H/sub 3/O/sup +/ to the departing oxygen, rather than unimolecular decomposition of the zwitterion H/sub 2/O/sup +/-CO/sub 2//sup -/ in the rate-determining step. 21 references, 2 figures.« less