Intracellular sodium in cardiomyocytes using 23Na nuclear magnetic resonance

• Published in: Biochimica et biophysica acta. Molecular cell research Vol. 1221; no. 2; pp. 133 - 144
• Main Authors: Ivanics, Tamas, Blum, Haywood, Wroblewski, Krzysztof, Wang, Dah Jyuu, Osbakken, Mary
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.03.1994; Elsevier Science
• Subjects: Biological and medical sciences; Cardiovascular system; Investigative techniques, diagnostic techniques (general aspects); Iodoacetate; Ischemia; Medical sciences; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; Shift reagent; Ischemia; Shift reagent; Iodoacetate; Heart; Rat; Rodentia; Biological marker; Cardiovascular disease; NMR spectrometry; Myocardial disease; Myocyte; Vertebrata; Mammalia; Analysis method; Sodium; Heart disease; Animal; Clinical biology; Intracellular; Quantitative analysis
• ISSN: 0167-4889; 1879-2596
• DOI: 10.1016/0167-4889(94)90005-1

Intracellular sodium content in superfused isolated rat cardiomyocytes was measured using 23Na nuclear magnetic resonance. The shift reagent dysprosium tripolyphosphate was added to the buffer to distinguish between NMR signals from the intracellular region and the extracellular buffer. The NMR visibility of the intracellular sodium signal was experimentally determined by measuring the changes induced in the sodium NMR signals by application of ischemia as an intervention. Intracellular volume was accounted for by determining the change in the sodium signal upon adding cells (in beads) to the buffer solution at the beginning of each experiment and by killing the cells (in beads) with Triton X-100 at the end of each experiment. The visibility of intracellular sodium (relative to extracellular) was 0.47 ± 0.12 (mean ± S.D., n = 12). The average intracellular sodium concentration using this visibility is 29 ± 4.5 mM ( n = 12). This value is much higher than results obtained by some investigators using NMR techniques and by others using different standard methods, with the exception of those methods which evaluate the total intracellular sodium (atomic absorption spectroscopy and X-ray microanalysis). We conclude that total Na i is higher than generally reported, using other accepted techniques such as ion-specific electrodes, and that 23Na-NMR analysis can be used to accurately determine Na i in intact cells.