Sodium TQF NMR and intracellular sodium in isolated crystalloid perfused rat heart

Abstract

The feasibility of monitoring intracellular sodium changes using Na triple quantum filtered NMR without a chemical shift reagent (SR) was investigated in an isolated rat heart during a variety of interventions for Na(i) loading. Perfusion with 1 mM ouabain or without K+ present in the perfusate for 30 min produced a rise of the Na TQF signal with a plateau of approximately 190% and approximately 228% relative to the preintervention level, respectively. Stop-flow ischemia for 30 min resulted in a TQF signal growth of approximately 147%. The maximal Na TQF signal increase of 460% was achieved by perfusion without K+/Ca2+, corresponding to an elimination of the Na transmembrane gradient. The observed values of Na NMR TQF growth in the physiological and pathological ranges are in agreement with reported data by other methods and have a linear correlation with intracellular sodium content as determined in this study by Co-EDTA method and by sucrose-histidine washout of the extracellular space. Our data indicate that the increase in Na TQF NMR signal is determined by the growth of Na(i), and the extracellular Na contribution to the total TQF signal is unchanged at approximately 64%. In conclusion, Na TQF NMR without using SR offers a unique and noninvasive opportunity to monitor alterations of intracellular sodium. It may provide valuable insights for developing cardioprotective strategies and for observing the effects of pharmaceutical treatments on sodium homeostasis.

Acute changes in extracellular volume fraction in skeletal muscle monitored by23Na NMR spectroscopy

“…In the rat heart during cardioplegic arrest, it was reported that [Na + ] i increased during ischemia only after an initial delay of 15 min (Schepkin et al. 1998). …”

“…In previous work, the proportion of the total TQF signal originating from the extracellular compartment was found to be between 30% and 60% of total TQF signal (Schepkin et al. 1998; Navon et al. 2001; Eykyn et al.…”

Competition between Na+ and Li+ for Unsealed and Cytoskeleton-Depleted Human Red Blood Cell Membrane: A 23Na Multiple Quantum Filtered and 7Li NMR Relaxation Study

“…This results in the detection in the DQF spectra of a broad negative component presenting a pair of overlapping dispersive lines of the satellites in antiphase, split by 2 Q (12). Anisotropic motion of Na ϩ ions has been detected using this method (30) in a variety of biological systems, such as RBCs (12,14), connective tissuescartilage, tendon and skin (13,(31)(32)(33), perfused rat hearts (22,34), rat brain (35), and in vivo human skeletal muscle and brain (25), as well as cartilage (36). In RBCs the anisotropic sodium binding sites are present at the membrane level in both the intra-and extracellular compartments and depend on the integrity of the cytoskeleton (12,14,37,38).…”

“…This biexponential relaxation behavior allows the creation and detection of multiple quantum coherences (9,10). MQF NMR spectroscopy of quadrupolar I ϭ 3 2 alkali metal nuclei has been studied extensively in macromolecular model systems (11)(12)(13)(14)(15) and in perfused organs, such as rat salivary glands (16), rat and guinea-pig hearts (17)(18)(19)(20)(21)(22), and rat liver (23). It was also applied to in vivo organs, such as rat liver (24), human brain, and skeletal muscle (25).…”

Time-Domain Quantification of Multiple-Quantum-Filtered 23Na Signal Using Continuous Wavelet Transform Analysis

“…The overwhelming advantage of multiple-quantum (MQ) filter techniques is that they allow noninvasive measurements and, thus, can be applied to humans. In general, some extracellular sodium signal also passes through a MQ filter (2); however, this signal is relatively insensitive to possible changes in extracellular sodium (3,4). MQF 23 Na MRS has also been used to probe structural information in partially disordered biological systems such as cartilage (5).…”