## Abstract Previous __in vivo__ studies have demonstrated that Ξ±, Ξ². and Ξ³ ATP chemical shifts measured by ^31^P NMR spectroscopy can be used to determine intracellular magnesium in erythrocytes, but up to now such results have not been confirmed in striated muscle __in vivo.__ We report __BATP__
Assessment of magnesium concentrations by 31P NMR in vivo
β Scribed by H. R. Halvorson; A. M. Q. Vande Linde; J. A. Helpern; K. M. A. Welch
- Publisher
- John Wiley and Sons
- Year
- 1992
- Tongue
- English
- Weight
- 583 KB
- Volume
- 5
- Category
- Article
- ISSN
- 0952-3480
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β¦ Synopsis
Abstract
^31^P NMR spectra obtained in vivo reveal the presence of a few reasonably well defined chemical species, namely, ATP, orthophosphate (P~i~), and, in brain, phosphocreatine. The chemical shifts of these resonances respond to changes in concentrations of ions such as H^+^ and Mg^2+^ in a manner that depends on both the chemical shifts intrinsic to individual complexes and the formation or binding constants for the several complexes. Values of the appropriate formation constants are well established in the literature. We have derived estimates of the chemical shifts intrinsic to the individual complexes by analyzing high resolution spectra of solutions whose composition brackets the domain of physiological relevance. This provides information sufficient to estimate intracellular concentrations of H^+^ and Mg^2+^ from chemical shifts seen with in vivo spectra. The primary finding is an estimate of 0.3 mM for the concentration of free magnesium in human brain. Differing values are obtained from other tissues.
π SIMILAR VOLUMES
Prior in vitro studies, utilizing 31P nuclear magnetic resonance (31P NMR) to measure the chemical shift (sigma) of beta-ATP and lengthening of the phosphocreatine spin-spin (T2) relaxation time, suggested an assessment of their efficacy in measuring magnesium depletion in vivo. Dietary magnesium de
The effects that haemoglobin-metabolite interactions have on estimates of free magnesium-ion concentration in human erythrocytes, determined by 31P NMR [Gupta, R. K. et al., J. Biol. Chem. 253, 6172-6176 (1978)], were investigated. If the metabolite-haemoglobin association constants of Berger et al.
Free cytosolic [Mg'] can be assessed in vivo by "P MRS from the chemical shift of &ATP which in turn depends on the fraction of total ATP complexed to Mg2+ ions. The reliability of these in vivo measurements depends on the availability of an appropriate in vitro calibration to determine the limits o
A technique to determine absolute metabolite concentrations of the kidney in vivo using 31P NMR is described. The technique is based on the use of methylphosphonic acid (MPA), which gives rise to a well-resolved peak upfield from in vivo phosphorous metabolite resonances, as an "internal standard."