23 Na double-quantum-filtered (DQF ) NMR enables the detecfound between the residual quadrupolar interaction and the tion of anisotropic motion of sodium ions due to their interaction conformation of the cytoskeleton (3, 4). In the present study with ordered structures in biological tissues. Using the technique, the relative contributions to the DQF and triple-quantumanisotropic motion was found for sodium ions in mammalian red filtered (TQF) spectra of sodium bound to anisotropic and blood cell suspensions (RBC ) and the effect was shown to correisotropic binding sites in the intra-and extracellular sodium late with the integrity of membrane cytoskeleton. In the present pools of human RBC were quantified. DQF spectra were study relative contributions to the DQF and triple-quantum-filmeasured by a modified Jeener-Broekaert pulse sequence tered ( TQF) spectra of sodium bound to anisotropic and isotropic which enabled exclusive detection of anisotropically moving binding sites in the intra-and extracellular sodium pools ( Na sodium ions (5). The relative contributions of the extracellucontent being 15 and 150 mM, respectively ) of human RBC were lar sodium to the TQF and DQF spectra decreased as the quantified for different hematocrits. DQF spectra were measured by a modified Jeener -Broekaert pulse sequence which enabled hematocrit increased, but their efficiency relative to the soexclusive detection of anisotropically moving sodium ions. The dium content increased. The contribution of the extracellular relative contributions of the extracellular sodium to the TQF and sodium to the DQF was, however, significantly smaller, and DQF spectra decreased as the hematocrit increased, but their was only 22% at a hematocrit of about 90%. efficiency relative to the sodium content increased. The contribution of the extracellular sodium to the TQF signal was found to MATERIALS AND METHODS dominate the spectrum of the RBC suspension at all hematocrits studied. The contribution of the extracellular sodium to the DQF
The study was performed on human RBC from healthy was significantly smaller than that to the TQF and was only 22% volunteers. Venous blood was collected with EDTA (35 ml at a high hematocrit of about 90%.